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Renew – User Guide - Fachbereich Informatik

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1. 2 3 Upgrade Notes These notes are supposed to help you when you have already installed an earlier version of Renew In Section 2 9 you can find a list of differences if you are interested in further details 2 3 1 General Note that you cannot usually read nets created with a later version by older versions of Renew However newer versions of Renew can read older files without problems I e an upgrade to the current version is simple but irreversible 11 2 3 2 Upgrade from Renew 1 5 or earlier Serialized shadow net systems exported by Renew 1 5 or earlier cannot be used with any later versions You can simply re export the net system A new keyword manual was added to the inscription language In rare cases you will have to rename a variable or package to account for this change 2 3 3 Upgrade from Renew 1 6 or earlier The required Java version has changed you need at least Java 1 4 to run newer versions of Renew You do not any longer need to install a separate XML parser like Xerces because Renew now uses the built in parser of Java 1 4 Saved simulation states exported by Renew 1 6 cannot be used with the current version of Renew Stubs compiled with Renew 1 6 or earlier cannot be used with the current version You can simply recompile the stubs and the resulting Java files Several classes of the Renew framework were moved or renamed In particular the class de renew simulator NetInstance has now become de renew net
2. The net from Fig 3 27 shows the basic algorithm of a juggler who wants to earn a few coins in a crowded mall He waits for spectators to come along and does a few tricks now and then This makes all spectators who were previously waiting happy and everybody contributes a fiver Try to load the net from the directory samples arcs and play around with it In the net implementation note that the variable x is bound to an array that holds all tokens of the place waiting during the firing of the transition We use the array to move 60 import samples reisig Doy Ixy t prod t neighbors x y pending Le guard z lt y xz xz guard z gt y show 0 n n o g show 1 n n o g show 2 n n o Figure 3 26 The net visualelection all the tokens to another place The array can also be used in ordinary Java computations if desired But because the set of tokens is determined only during the transitions firing a variable attached to a clear can only be used in an action inscription but not in guards in other transition inscriptions or in arc inscriptions A clear arc takes effect after all other input arcs have been evaluated This means that you can remove some tokens from a place using ordinary arcs and then remove the remaining tokens with a clear arc In the given net you may use this feature by adding an ordinary arc from the place waiting to the tra
3. Cad r Terminate Simulation gt 7 Cmnd Option B Set Breakpoint te id Option C Clear Breakpomt 6 gt Window S O Cmd R R So E Cmd 1__ Simulation Step Cind ShiR 1 Simulation Net Step Window Cmd M__ Bring Memo Front TSS Alphabetical List a Apple Specific b build in c customizable r reserved s switching simula tion editing p provided by optional plugin Gnd Align Middes e gt gt gt Cm 7 Spread Diagonal PB d Ca 0 PNG Espore gt Export Cmd i group Net Component p Net Components Cmd 3 ingroup Net Component p Net Components Cm Spread Middles fe 7 Cmd Spread Centers fe SSS Gnd a Select MSs CS Cnds B Bring to ont o ooo i Cad B_ Send to Back o Cmd Option B Set Breakpomt bs Cinc Option B Set Breakpomt bs Cmd Option C Clear Breakpomt b Cmd Option O Clear Breakpomt bs gt gt gt w pa Tay o CCS Ca b Doia Sid E EPSE p n F fsa 1 3 AE O Search ERa b Simulation Net Step b 7 Simulation Step b _ Layout Check gt _ EE ie Ea E Cmd Shift Cmd Shift Cmd MEN EA Cd 7 i AA eoo Eoo a LO Open Drawing b Cmd Shift E F H I I L M N R H m T E M__ Bring Menu to Front N CA e R 119 Gnd S Save Drawmg s d gt SSCS Cmd Shit_ S Save Drawing As b CmdOpion S Syntax Check o SSS Cod
4. This menu entry stops the current simulation run if there is any For certain reasons the simulator can not know if the simulated net is dead it could always be re activated from outside see Section 3 9 so a simulation only ends when you invoke this command When you issue another simulation command after this command a new simulation is automatically started All simulation related windows net instances current markings now also possible transi tion bindings are now automatically closed when simulation is terminated since they cannot be used after simulation anyway The keyboard shortcut for this function is Ctr1 T Configure Simulation Renew This dialog allows to change some simulation related configuration options These 2 0 options can also be controlled from the command line or the configuration file renew properties see section 2 6 1 All options presented in this dialog are evaluated each time a new simulation is started However the settings in this dia log are not stored permanently The dialog comprises several tabs each tab groups some configuration options The buttons at the bottom of the dialog affect all tabs 98 Apply passes the current settings to the plug in system so that the simulator plug in can interpret them at the next simulation startup Update refreshes the dialog to display the current settings known to the plug in system Unless you modify some properties concurrently you can think o
5. A last operator that must be mentioned is instanceof Its left operand is an expression as usual but its right operand must be the name of a class or interface It evaluates to true if the result of the expression is a reference to an object of the given class or one of its subclasses or of a class that implements the given interface With an object reference you can also inspect fields and invoke methods E g if there is an object o with a field f you can access the field by writing o f inside a Java expression The result will be the current value of that field For an object o a call of the method m with the parameters 1 and x would look like o m 1 x This has the result of binding the formal variables to the parameter values and executing the body statements of the method Unless the method is of the return type void a return value will be calculated and returned Due to overloading there might be more than one method of a given name within some class In that case the method that matches the parameter types most closely is invoked In order to create a new instance of a class you can use the new operator E g the expression new java lang StringBuffer will create a new object that belongs to the 41 guard i gt j amp j gt 0 i i j Figure 3 4 The net gcd class java lang StringBuffer and invoke its constructor A constructor can be seen as a special method that initializes a new object The new operator can take arguments
6. DM ae an ok hacer ary RN E E 78 Bote chet ie EE oer Se ae Sy aera ed ance eae ie ue le ae cs A 84 ge ase as eho Se aid reia be ele aps quo Gade cs Oe eee A 86 RA E 89 A5 A A A A 92 A ita des a a 97 EAT he eee eas 104 A ac E ho Shoe ae Rs 104 AAA oe Pe Aen oe E 104 4 5 1 Net Instance Windows 104 ee ae ee a ee E 105 ed wees a ae hea oo 105 66 adie Me ra ee 106 tides Apne ee eters a he Ba 107 4 7 1 Parser Error Messages o aoa a a a a a a a 108 e She eh ee Oe Gane Sek 108 bas ne eee ee dears eee a ee 112 A Contacting the Tea 116 B File Type 117 C Keyboard Shortcut 118 i 121 AA 121 paria 121 A 121 AI 121 A ee A 122 NA gee ee eS 122 ON of ea pa aes a Gece de ce de a 123 IS ee 124 Te Serre a ee re ee re te ee ee 124 DIA 124 AP eee ee as 124 Ah a os ete bod el oe eG eG ee ee 124 ie bb ee Be dd a oe ee ee de da 124 os se Whee A ed eats ee eee 125 List of Figures PEE AN E A E A A as as Be a a a a 3 11 The net othernet Shed Ae eee eee ee ba a 3 18 The net account itn PP corn oa ene ae 4S E A o a io Boe cod dea o Aa ciao aces ok Aa Saas 3 29 The net port bo ee ak eS we hk ee ew we ee 4 1 The Renew Window 000 a ee 4 2 The Petri Net Toolbar in its own Windo 4 3 The Renew Navigatoy 0 0000 a 4 7 The Santa Claus Example with Icons During Simulation List of Tab
7. How ever the execution of those transitions that are already firing continues This is especially important if a breakpoint is attached to a transition The transition might still run to com pletion while the breakpoint is reported That means that you will often want to attach a breakpoint to an input place of a transition if you want to inspect the state of the net before a certain transition fires You cannot currently detect a change of enabledness directly Set Breakpoint at Selection Before setting a breakpoint you must select a place or transition or a group thereof within a net instance window You can set a breakpoint either locally or globally A local breakpoint will affect exactly the chosen net instance and will not cause a simulation stop if other net instances change A global breakpoint automatically applies to all net instances even those that will be created after the breakpoint is established There are a number of different breakpoint types e Default This is a convenience type that is equivalent to a breakpoint on start of firing for transitions and on change of marking for places You can use it if you want to set a breakpoint to a place and a transition simultaneously e Firing starts This breakpoint is triggered whenever the transition starts firing The breakpoint happens just after all input tokens have been removed from their places and the transition is about to execute its actions e Firing completes Unli
8. If you just click the image is inserted using its original dimensions in pixels otherwise it is scaled to the rectangle area specified by your drag operation An image figure has the same handles as a rectangle figure The Text Tool The text tool is used to arrange text with your graphical elements The first mouse click after activating the tool selects the upper left corner of the text area and invokes a text editor Now you can type in any text including numbers symbols and so on You can even use the cursor keys delete any characters select some part of the text with the mouse and so on like in any other Java edit field Note that you can even type in several lines as usual by pressing the return or the enter key This is why pressing return or enter does not end the edit mode After you click somewhere outside of the text editing box the text is entered and all of the text is displayed If the editing box is empty at that moment the entered text comprises white spaces and line breaks only the text figure is automatically removed from the drawing The white box handles are just to show that a text figure is selected The dimension of a text figure can not be changed as it only depends on its text contents and font selection The only handle to modify a text figure is a small yellow round font sizing handle It can be dragged to alter the font size which can also be done using a menu command see Section 4 4 4 74 If you
9. Renew Tf you move outside a drawing window while operating with the mouse i e while 2 2 the mouse button is held down the viewable area of the drawing is scrolled until the drawing bounds are reached If you are dragging a figure or handle downward or rightward beyond the current drawing bounds the bounds are pushed forward until you either release the button or move the mouse back into the window 67 4 2 Basic Concepts When working with Renew you edit so called drawings A drawing consists of many drawing elements called figures Each drawing is displayed in a separate drawing window Since you are expected to work on many different drawings and thus have many different windows open at the same time it would consume lots of valuable desktop space to repeat a menu bar and tool buttons in every window To avoid this all commands have been grouped into one central window the Renew window which contains a menubar a toolbar and a status line see figure 4 1 This might seen a bit unfamiliar for Mac users but is related with the platform independence of Java Renew The shortcut Ctr1 M activates the central Renew window and brings it on top of 2 2 all other windows This key is useful if you are working with many large drawing windows these buried the central window and you need access to the menu bar or tools Reference Net Workshop File Edit Layout Attributes Net Simulation Plugins Windows Help NON A Le A om A AL SINIS ilan
10. if you use the Mac OS X application bundle this directory is located inside the application package at the path Contents Resources Java plugins If the plug in comprises several files one of which is the file plugin cfg then you can create a subdirectory below e g renew2 4 3 plugins myplugin and copy all files in this directory On the next startup the plug in system will find and include the plug ins automati cally If you want to include the plug in in the running system use the load command see Section 2 7 4 in addition 24 If you do not want to install the plug in to your renew distribution directory you can install it to some other directory let s say home myself devel myplugin jar as single jar plug in or home myself devel myplugin as multi file plug in Then you again have two possibilities To make the plug in system aware of the plug in at the next startup add the line pluginLocations home myself devel to your renew properties file see Section 6 1 for details When entering multiple paths they must be separated by the system s path separator which is on Windows and on Unix systems To load the plug in immediately but temporarily into a running plug in system use the load command Depending on the number of files comprising the plug in it s one of the following commands load file home myself devel myplugin jar load file home myself devel myplugin plugin cfg 2 7 2 Exclud
11. opers may use these properties to replace the default implementations by enhanced versions The server class determines the simulation control features which are remotely accessible The socket factory may enhance RMI transmissions by compression and or encryption of the network traffic All properties except socketFactory are re evaluated at each simulation setup They are configurable at runtime in the editor s Configure Simulation dialog see Section 1 4 6 Renew The renew property de renew remote rmi host name can now be set to define the 2 4 rmi server hostname to the correct ip if the remote server cannot be found It is similar to the java property java rmi server hostname 2 6 10 Logging Renew Starting with release 2 1 Renew uses the Log4j package from the Apache Logging 2 1 Services project I to give detailed feedback about its activities The Log4j frame work allows users to tailor the logging output to fit their needs The level of detail can be configured for every application package or class individually The Renew base installation contains a binary distribution of Log4j in the renew2 4 3 libs directory The package is loaded immediately at application startup before any configura tion of the plug in system is done The early load time of this package has the consequence that the enhanced configuration methods mentioned at the beginning of this Section are not applicable to configure the logging system Configuration mec
12. special subclass like inscriptions see Section 1 3 3 The Inscription Tool to a new parent Whenever the landing point of a connected text drag operation is another potential parent it is selected immediately to indicate that instead of changing the offset to the old parent the targeted figure will become the new parent of the connected text figure as soon as you release the mouse button If you drag the connected text figure to a location outside this new parent again its old parent if there is any is selected in the same manner to indicate if you let go the mouse button now the parent will stay the same Note that the offset the connected text figure had to its old parent is re established for its new parent so it might jump to another position after reconnection This is quite convenient if you moved an inscription to a preferred offset to its parent e g to the right hand side of a transition and want to keep this offset even after connecting it to a new figure 4 3 3 Net Drawing Tools Now it is really getting interesting This group of tools allows you to draw Petri nets that have a semantic meaning to the simulation engine Renew differentiates between a simple rectangle and a transition although they may look the same When you use the net drawing tools some syntactic constraints are checked immediately see Section 4 7 A Since all net element figures transitions places and arcs may have inscriptions Y Renew sup
13. then 2147483646 then 2147483645 until a binding of an integer variable is found Instead variables that occur as inscriptions to input arcs are bound to the values that occur as tokens in the corresponding places This leads to an important design rule Always make sure that the bindings for all variables can be determined by binding input arc variables to tokens Remember that the simulator 64 r _ One n guard buffer length gt 10 O buffer buffers buffer new StringBuffer puffer buffer append Figure 3 31 The net buffer does not evaluate expressions backward Remember that flexible arcs do not contribute to variable bindings If the simulation engine does not manage to bind a variable in this way it simply gives up and declares the transition disabled In some other Petri net formalisms unbound variables are used as a sort of random generator While this may be a good idea sometimes it is not difficult to simulate this behavior by a direct call to a random number generator Closely related are spelling mistakes for variable names In the untyped formalism every identifier is a legal variable name therefore many spelling mistakes cannot be detected Often this leads to unbound variables and completely disabled transitions although all tokens seem to be in place In fact Fig 3 30 contains such an error because in one place authorAddr is misspelled as authotAddr 3 12 3 Side Effects It has already been noted that side
14. 2 2 image file which can be displayed by many modern web browsers Petri net semantics are not retained The SVG export is based on the FreeHep library 82 Macao Macao see 12 is a graph drawing editor with connection to the FrameKit platform see http move 1ip6 fr software FRAMEKIT This function is probably of use for a very limited number of people and still in beta status Do not expect every Renew net to be mappable to Macao This function can merely be used to check the net structure of a single net Also you may have to manually adjust inscriptions etc Exported nets in Macao format can not be read with Macao version 3 0 2 They might be readable by earlier versions of Macao However they can be used as import format for the Coloane Eclipse plug in https coloane 1ip6 fr which is an alternative graph editor with connection to the FrameKit platform Woflan Woflan see 7 is a Workflow Analysis tool that checks if a Petri net conforms to some restrictions that make sense for Workflows As Woflan only handles single non colored Petri nets without synchronizations only the structure of the active window s net is exported Still if you have the Woflan tool it makes sense to check Renew workflow models for severe modeling errors in their structure For the time being the initial place of the workflow net must carry the name pinit Otherwise a place with this name but without any connected arcs will be
15. An inhibitor arc however does not contribute any information about possible bindings to the simulator i e all variables used in the inscription must be determined by other inscriptions It is not possible to inhibit whole groups of token values e g to make sure that no tuples whose first component is a given value are contained in a place But this can usually be simulated by providing a second place that stores only the first components of the tokens and that is updated consistently with the original place In Fig 3 28 a typical use of inhibitor arcs is shown In the place at the top a filetype is given and the system has to decide whether this is a known file type All known file types are supposed to be registered in the place at the lower center Now the left hand transition selects the known file types whereas the right hand transition can only fire if the filetype is not contained in the center place Using ordinary Petri nets it is rather difficult to express such a constraint Note however that inhibitor arcs lack a robust concurrency semantics so that they have to be used with the extended sequential mode as described in Subsection 2 6 5 3 11 Timed Nets While pure Petri nets capture the causality and conflict situations of a system nicely there are reasons to add a notion of time to the formalism in order to model additional dependencies This is especially true in the case of simulations of physical systems Renew To en
16. NetInstance If you use typed variables for net references in your nets you must adapt the variable declarations or package imports When a new net is created the newO is no longer implicitly invoked It is only invoked when you create the net using the notation n new NetName as opposed to n new NetName You might have to rewrite some nets as a result of this change The way of including custom classes in a Renew simulation has changed please read Section 2 6 6 for more details 2 3 4 Upgrade from Renew 2 0 2 0 1 or earlier The main application class has been changed from de renew plugin PluginManager to de renew plugin Loader There are now two configuration file locations first the per installation configuration file renew2 4 3 config renew properties is read then the user specific file renew properties is consulted The property pluginLocations has been changed to a classpath like syntax see Section 2 71 The net loader priorities have changed instead of preferring sns files over rnw files regardless of the order of their directories in the de renew netPath property now the order of directories is considered first while the order of file types is undetermined The Renew code has been modified to compile without warnings under Java 1 5 but we still use Java 1 4 2 The conformity with Java 1 5 also implies the use of an up to date version of JavaCC during compilation The old collections package has been removed from al
17. T Terminate Simulation b Ca y pe S Coad W Cose Window pe SS x o S Ca z oos h ooo Gnd __ Align Center pe SS Toggle Key Mappings for Main Drawing Tools By setting the property de renew keymap use mapping true the following keys can be used to select the main Renew tools Selection Tool t Transition Tool p Place Tool v Virtual Place Tool a Arc Tool x Test Arc Tool r Reserve Arc Tool f Flexible Arc Tool i Inscription Tool n Name Tool d Declaration Tool 120 Appendix D License We refers to the copyright holders You refers to the licensee Renew refers to the complete set of sources executables and sample nets that make up the Reference Net Workshop Renew is available free of charge but not without restrictions The majority of Renew is published under the GNU Lesser General Public License for details see Section Original Parts below However Renew builds up on other people s work that has been licensed under other terms The license section got a bit long We apologize but we cannot hope to do better because we included many external parts with many different licenses D 1 Contributed Parts Renew uses several parts that were previously developed by other people and have been made publicly available D 1 1 The collections Package The collections package is used as our set queue list implementation The relevant license information states Ori
18. a net drawing mime type application x renew net rst a saved simulation state mime type application x renew state sns a serialized shadow net system mime type application x renew sns stub a net stub description sty a T X style definition tex a TEX source file zip a ZIP compressed archive 117 Appendix C Keyboard Shortcuts List by Category a Apple Specific b build in c customizable r reserved s switching simula tion editing p provided by optional plugin Cm N New RW S Lomas N Open Navigator p Navigator Cmd 0 Open Drawing b 7 Cm S Save Drawing o gt gt Onda 8 Save Drawing As b Cm W Close Window Je Cm E EPs Export Export Cnt Shi P PDF Epo p Export Cmd oo PNG Export Cmd Q Quit Program ra oo Edit Cmd Cmd ma Jo Gad v Cmd D__ Duplicate Cmd F Search Search amp Replace Select All Cmd Finish Editing Layout see below for customization options Cmd Send to Back Bring to Front Align Center Align Middles Spread Centers Spread Middles Spread Diagonal F Search Cmd pb Cmd b Cmd b Cmd b Cmd e Cmd b P b Cmd b pb b b 118 Net Cmd Option Cmd Option Cmd Option Cmd Option Simulation Set Breakpoint Clear Breakpoint Syntax Check Layout Check C S L vnan Run Simulation b Simulation Step b Cmd Shift Simulation Net Step b
19. all other commercial damages or losses even if such Contributor has been advised of the possibility of such damages D 1 7 The FreeHEP VectorGraphics package Renew comes with a slightly modified version of Java libraries provided by the the FreeHEP project to support several export formats like EPS PDF SVG or PNG The FreeHEP libraries are provided under the same license as Renew itself the Gnu Lesser General Public License for a link see below which allows the inclusion of a binary distribution within other projects The modified sources are available at https github com renew tgi D 2 Original Parts This copyright section deals with those part of Renew that are not based on other works i e the example nets and the packages fs and de renew without the JavaCC grammars D 2 1 Example Nets The example nets are in the public domain You may modify them as you like You may use them as the basis for your own nets without restrictions D 2 2 Java Source Code and Executables Sources and executables are copyright 1998 2015 by Olaf Kummer Frank Wienberg Michael Duvigenau Lawrence Cabac and others You can distribute these files under the GNU Lesser General Public License You should have received a copy of the GNU Lesser General Public License along with this program in the file doc COPYING if not write to the Free Software Foundation Inc 59 Temple Place Suite 330 Boston MA 02111 1307 USA D 3 Created Parts You ar
20. and ARM files are also shown by the navigator 2 4 Usage of the Navigator At the top of the naviga tor window is an iconbar with eight buttons We de 000 File Navigator scribe these buttons and their function left to right m ED Bl ey x The Home button displays the home directory El FireExtinction rnw which defaults to the preconfigured files see next 11 Fireman rnw paragraph or if there are none to the current direc gt icon tory The NetPath button displays all folders which gt Gi pitfalls are included in the netpath of Renew This is usu gt 3 prosecute v Greisig t election rnw 11 visualelection rnw ally empty but can be set when starting Renew or in the menu Simulation gt Configure Simulation gt Net Path The Add Folder button opens a file choose dialog and adds the chosen directory or file to the gt 3 simple v time tree El port rnw gt J tuple Renew The Expand button expands the complete i folder structure The Collapse button collapses all nodes of the tree The Refresh button checks for new and deleted files and updates the display in the tree area The Remove button removes a single node from the tree while the Remove all button removes the whole tree Figure 4 3 The Renew Navigator Configuring the Navigator The navigator has two properties that can be configured in the usual configuration files de renew navigator workspace and de renew navigator filesAtStartup Th
21. and array or a list The compiler was able to determine that the given expression will always evaluate to null Maybe the inscription is attached to the wrong net element Maybe the arc was not intended to be a flexible arc 111 Only one declaration node is allowed You have two or more declaration nodes in your net drawing In general the simulator cannot determine in which order multiple declaration nodes should be processed hence this is not allowed Maybe a declaration node was duplicated unintentionally Maybe you want to merge the nodes into one node Output arc expression for typed place must be typed A typed place must only hold values of the given type An untyped output arc is not guaranteed to deliver an appropriate value so this might lead to potential problems Maybe you want to type your variables Maybe you want to remove the typing of the place Place is typed more than once At most one type name can be inscribed to a place Multiple types are not allowed even if they are identical Maybe a type was duplicated unintentionally Time annotations are not allowed The compiler detected an annotation of the form but the current compiler cannot handle such inscriptions which require a special net formalism You should switch to the Timed Java Compiler see Subsection 4 4 6 Transition has more than one uplink At most one uplink can be inscribed to a transition Maybe an uplink was duplicated unin tentionally Mayb
22. and thus defines several points which are connected by lines You can also define single points by single mouse clicks The creation mode is ended by double clicking at the last point or right clicking in the drawing window The clou about the scribble figure After it has been created every single point can still be changed by dragging the corresponding white square handle To drag the whole figure start dragging on a line segment rather than inside a handle or deselect the figure first and then start dragging anywhere on a line of the figure The Polygon Tool A polygon is created analogous to a scribble figure see above While you create the polygon you can already see that the area surrounded by the lines is filled with the fill color In contrast to the scribble figure the surrounding line is closed automatically By intersecting the lines you can create un filled areas Like in the scribble figure there are white square handles to 73 drag every single point of the polygon figure A new function is that a point that is dragged to somewhere on the direct line between its ancestor and predecessor point is removed from the polygon Also there is a new round yellow handle that can be used to turn and to scale the entire polygon figure by dragging the handle which looks really nice thanks to Doug Lea Renew The round yellow handle is restricted to pure rotation as long as the shift key is 2 2 pressed and to pure scaling as long a
23. arc inscription When a transition fires its arc expressions are evaluated and tokens are moved according to the result Transitions can be equipped with a variety of inscriptions Expression inscriptions are 37 Figure 3 1 The net elements int 49 guard x y Figure 3 2 The net colored ordinary expression that are evaluated while the net simulator searches for a binding of the transition The result of this evaluation is discarded but in such expressions you can use the equality operator to influence the binding of variables that are used elsewhere Guard inscriptions are expressions that are prefixed with the reserved word guard A transition may only fire if all of its guard inscriptions evaluate to true With these additions we cover the basic colored Petri net formalism In Fig B 2 which is also provided in the directory samples simple we find a net that uses the basic place and arc inscriptions At the left we have a place that is typed int which means that it can only take integers as tokens In this case it has an initial marking of one integer 42 token The other places are untyped and initially unmarked The leftmost transition will take 42 out of the place and deposit one 4 and one 2 into the respective places The upper middle transition takes some x which happens to be 4 in this case out of its input places and copies it into its two output places The lower middle transition is similar but here the equality of
24. are not as easy to understand We postpone the description of these arcs until Section 3 10 Each place or transition may be assigned a name Currently this name is used only for the output of trace messages By default names are displayed in bold type In Fig 8 1 you can see a net that uses all net elements that were mentioned so far You can find it in the directory samples simple of the Renew distribution A single place p is surrounded by six transitions Initially the place is unmarked Assume that transition a fires which is always possible because all its arcs are output arcs Now one token is placed in p and all transitions except c are activated Transition c is still disabled because it reserves two tokens from p while it fires In contrast to this transition e may fire because it is allowed to test a single token twice If a fires again transition c becomes activated too because a second token is now available A firing of the transitions b c e and f does not change the current marking However transition d will remove one token from p during each firing Every net element can carry semantic inscriptions Places can have an optional place type and an arbitrary number of initialization expressions The initialization expressions are evaluated and the resulting values serve as initial markings of the places In an expression denotes a simple black token By default a place is initially unmarked Arcs can have an optional
25. are not equal In Fig 3 9 you can see an example net which reverses a list by successively splitting off the head of the original list and appending it to a result list The remainder of the original list and the result list are jointly contained in a tuple Once the original list is fully consumed the result list is extracted 3 6 Net Instances and Net References When a simulation run of a net is started the simulator creates a net instance of the net that is simulated A net that is drawn in the editor is a static structure However an instance of the net has a marking that can change over time Whenever a simulation is started a new instance is created Most net formalisms stop here They create one instance of a net and simulate it Renew allows you to create many instances of a single net Each instance comes with its own marking and can fire independently of other instances Every net has a name The name is derived from the file where it is saved by removing the directory name and the suffix E g a net saved in users foo bar baz rnw would have baz as its name New net instances are created by transitions that carry creation inscriptions which consist of a variable name a colon the reserved word new and the name of the net E g x new baz makes sure that x is bound to a fresh instance of the net baz In Figs 3 10 and you can see a simple example These nets are available in the samples creation directory When you st
26. as this feature is on the plug in system will not terminate automatically because there is no active plug in see Section 2 7 3 However an explicit termination request will still be executed keepalive off turns the keep alive feature off keepalive without argument displays the current state of the keep alive flag The initial state of the keep alive flag is determined from the value of the property de renew prompt keepalive If you tend to use the prompt as your only active plug in most of the time you should consider adding the line de renew prompt keepalive true to your renew properties configuration file As an alternative to the command line prompt there also exists a gui prompt plug in for download This plug in adds a small dialog to the Plugins menu of the editor which accepts commands to the plug in system Renew The graphical prompt automatically keeps the plug in system alive as long as its 2 1 dialog is open The dialog can also be opened by the command line command guiprompt The command feedback is now visible in the dialog instead of the Java console window 27 Renew Jt js possible to escape whitespace characters by surrounding double quotes or with a preceding backslash e g gui foo bar file rnw or gui fool bar file rnw 2 7 6 Net Components Net Components NC are sets of net elements Figures that are grouped in a flat and weak fashion The aim is to be able to allow to move the whole set of net ele
27. but it will not show up in a drawing window on the screen Matching shadow net system files must contain a single net with the same name alone If more than one net is found in the shadow net system file it is rejected to avoid confusion about the source of compiled nets There is a command in the menu File Export Export all single file each to generate such single net shadow net system files for all open drawings see Subsection 4 4 1 When the simulation has been started via the Simulation menu in the editor and only then the net loader will also look for rnw files in the netPath If it finds a matching drawing file the drawing shows up in an editor window and is immediately compiled into the running simulation Renew Ifa net can be obtained from several different sources at the same time the net 2 1 loader takes the first one in the order of the netPath entries If it encounters sns files in the same directory as rnw files with the same name it is not defined which one gets loaded The editor also uses the net loader during simulation to open drawings from rnw files that are needed to display net instances But you should be aware that the net loading feature comes with a big pitfall If sns files and rnw files are not kept up to date compiled nets in the running simulation may have a different structure than the nets shown in the editor Since the mapping from a simulated net to its drawing is based solely on the net name it
28. by a listener E g a button triggers a java awt event ActionEvent that is handled by a java awt event ActionListener public interface ActionListener implements java util EventListener void actionPerformed java awt event ActionEvent Of course a net could implement the ActionListener interface but there is a catch The call to an event listener blocks the entire Java windowing thread such that no events can 54 o action frame new java awt Frame action frame setSize 300 300 En action frame show action changer changer lt new samples call SizeChanger frame Pa frame East small O Center close N Pa West large gt frame f a A location type changer y ype a action button new java awt Button type action frame add button location frame action button addActionListener changer action button setActionCommand type frame En action frame validate Figure 3 20 The net buttonmaker be processed before the listener completes the method call Because further user interactions might be needed to trigger the next simulation step we might run into a deadlock To solve this problem we may denote that a method should return before its synchronous channels are invoked The channel calls are then processed in the background where they do not block other tasks Of course this is only possible for void methods because other methods must first compute their return val
29. by the menu entry Simulation Configure Simulation contains a checkbox named Sequential mode and a box where you can change the engine multiplicity for details see Section 1 4 6 These two elements in combination represent the current value of the property de renew simulatorMode and its value is changed when you press the Apply or OK buttons As a fourth way to set properties the plug in system provides a set command This command comes in useful in combination with the script command see Section 2 7 or if you installed one of the prompt plugins Although this command allows to set values for any known and unknown property at runtime it is not guaranteed that the value change has any effect In fact many properties are evaluated only once at startup time As a rule of thumb all options that affect the simulation behavior are evaluated at each simulation setup For example the command set de renew simulatorMode 1 has no effect on a simulation currently active if there is any But the next time you start a simulation from within the running application it will be sequential When you configure properties at runtime any setting of that property from the command line or the configuration file is overridden Runtime settings are not stored permanently 2 6 2 Drawing Load Server Many users like to load documents into the corresponding application just by double clicking the document in the file manager A typical problem is that this
30. drawing The keyboard shortcut for this function is Ctr1 E 81 Renew The EPS and Postscript export feature relies on the VectorGraphics package of the 2 2 Free HEP project see java freehep org This choice enables some of the features that lacked the de renew util PostscriptWriter class by Frank Wienberg that we have used before However there are still some issues as of VectorGraphics 2 1 Generated files are larger than before exported figures are still always opaque in postscript based export formats and the font embedding feature is incomplete The Renew FreeHep Export plugin provides the de renew io export epsFontHandling configuration property which can be set to Embed Shapes or None The Shapes option is the default as it produces the most similar output with respect to screen display However the generated files can become rather large The None option comes close to the old Renew export behavior without any font information included The Embed option should be the best theoretically but it often produces unreadable results Renew The background of drawings exported to eps can also be set to transparent by setting 2 A the property de renew io export eps transparency to true PNG Renew This function produces a PNG image that contains the current drawing A file 2 2 with the default extension of png is generated This export format differs from the previously mentioned formats since it is pixel oriente
31. effects must only occur in action inscriptions However there is another tricky point The enabledness of a transition must not depend on a mutable property of a Java object In Fig 8 31 we have a net whose modeler is guilty on both accounts It was intended to have a string that grows and grows and that some other transition should fire as soon as the length of the string exceeds 10 But if you run the net you will find out that the upper right transition never fires Or at least it is very improbable that it fires This is because it is checked for enabledness early on while the string length is still 1 or 2 Afterward it is not rechecked because its input place did not change its marking It is also possible that the length of the string increases by 2 during some cycles How can that be The call to append is not contained in an action so that could be evaluated once during the search for a binding and once during the actual firing Note that this is a relatively harmless scenario 3 12 4 Boolean Conditions The standard way of ensuring the equality of two expressions is the transition inscription expri expr2 But note that the inscription expr1 expr2 does not lead to inequality It is merely a boolean expression that is evaluated and whose result is discarded If you want to specify inequality you have to use a guard like guard expr1 expr2 3 12 5 Custom Classes It is often sensible to encapsulate complex operations in helper class
32. expand a directory sub tree The Navigator now loads directories without locking the GUI PNML and ARM files are shown in the Navigator The keyboard shortcut Ctrl Enter closes the text editor overlay 35 The background transparency of EPS files can now be controlled by setting the property de renew io export eps transparency For Windows the installation script installrenew bat creates reg files that associate and disassociate Renew drawing files with loadrenew bat and register icons We provide deb packages for Debian based systems Relevant for Developers We refactored large parts of the code base Many Java compiler warnings have been re solved and Javadoc documentation have been improved A few more JUnit tests have been introduced Logging and the simulator have been partially reworked to allow deadlock free real time GUI logging with only minimal time delay Several tools that were originally mandatory to build Renew are now optional these are Cobertura Jalopy JUnit and Latex 2 9 16 Changes in Version 2 4 1 This is a maintenance release that provides a fix for a race condition that occurs under rare conditions during the termination of the simulation 2 9 17 Changes in Version 2 4 2 This is a maintenance release that provides a fix for the import of reference nets from PNML format RefNet 2 9 18 Changes in Version 2 4 3 This is a maintenance release that provides an update of the FreeHep library and a new ver
33. figure These handles let you change the dimension and location of a figure after you created it Depending on the position of the handle only certain changes are allowed For example the east sizing handle only allows to change the width of a figure while maintaining the location of the left side and the south west sizing handle only lets you relocate the lower left corner of a figure while maintaining the location of the upper and right side Renew The south east handle restricts itself to sizes of equal height and width squares as long as the control key is pressed The control key can also be used as a modi fier while you are working with the rectangle creation tool and many other figure creation tools All newly created figures have a black outline and aquamarine as the fill color if there is any To change these attributes use the Attributes menu see Section 4 4 4 To create figures with the same attributes as an existing figure use copy amp paste see Section 4 4 2 The Round Rectangle Tool The round rectangle tool works the same way as the rectangle tool see above only that the created figure is a box with rounded corners A round rectangle figure has the same handles as a rectangle figure plus an additional single round yellow handle to change the size of the curvature Drag this handle and change your round rectangle to anything between a rectangle and an ellipse 71 The E
34. handles Just drag one of these handles to the new start or end figure If you release the mouse button while the connection is not snapped into a new figure the connection will jump back into its old position 72 An advanced feature is to produce intermediate points or pin points in a connection When selected connection figures show additional insert point handles to create new inter mediate points in the middle of each line segment These are depicted as small circles with a cross plus sign inside When you click on an insert point handle a new location handle see below is created within the given line segment and can immediately be moved By holding Ctrl while pressing holding and dragging an intermediate point you can orient the two emerging line segments in a right angle A different method to create and delete intermediate points is to use the connection tool Activate the tool and click on a point on the connecting line Now a new location handle white square is created which you can see the next time you select the connection figure This handle can be dragged to an arbitrary position When you hold down the control key while moving a location handle the intermediate point jumps to the closest position so that the adjacent line segments form a right angle You can also keep the mouse button pressed down right after clicking on an intermediate point and drag the new handle immediately without actually ha
35. individual nets that communicate via synchronous channels 3 12 Pitfalls A few common and especially dangerous pitfalls will be discussed in this section 3 12 1 Reserve Arcs and Test Arcs Reserve arcs and test arcs look alike because they do not change the marking of the associated place This can lead to subtle modeling errors The net from Fig 3 30 which is filed in the directory samples pitfalls shows a small excerpt of a workflow when a printing error is found in an article in a book The desired effect is to lookup the address of both author and editor so that they can be sent a notification The modeler wanted less net elements therefore both lookups were done by a single transition However the database access is done with a reserve arc so that this procedure fails when author and editor coincide In this case it would have been better to use a test arc because there is no need to reserve the information in the database This error which is not the only one in the net is especially difficult to detect because it is hidden behind a synchronous channel invocation Use test arcs to access information use reserve arcs to access physical items or logical resources 3 12 2 Unbound Variables The main task of the simulation engine is to find bindings of the variables under which a transition becomes activated However the simulation engine never tries to bind variables blindly to all possible values e g trying 2147483647
36. inside the parentheses The arguments are then passed to the constructor just as in an ordinary method call 3 4 The Inscription Language Because we are dealing with a colored Petri net formalism the net simulator must determine which kind of token is moved for each arc The possible kinds of tokens are Java values or references By default an arc will transport a black token denoted by But if you add an arc inscription to an arc that inscription will be evaluated and the result will determine which kind of token is moved 3 4 1 Expressions and Variables Arc inscriptions are simply Java expressions but there are a few differences The first dif ference concerns the operators that are used in expressions In Java the binary operators amp amp logical and and logical or are short circuit operators I e if the result of the left operand determines the result of the operator the right operand is not even evaluated This would imply an order of execution which we tried to avoid in our net formalism Hence the two operators are not implemented The same holds for the ternary selection operator An additional benefit of its exclusion from the language is that this frees up the colon for other syntactic constructs Possibly these three operators might still occur in later releases of Renew In Java variables receive their value by assignment After a second assignment the value from the first assignment is lost This flavor
37. is possible that transitions and places in a net instance window do not fire in accordance to the visible net structure Renew The de renew netPath property is re read every time a simulation is started It 2 0 is configurable at runtime in the editor s Configure Simulation dialog see Sec tion 4 6 2 6 8 Database Backing You can run Renew using a database that keeps a persistent copy of the current simulation state In the case of a system crash this allows you to continue the simulation from a valid state just before the crash when Renew is restarted Database backing is only supported when the simulation is started from the command line see Section 1 6 for information on controlling a simulation from command line Using database backing in gui mode may lead 21 to unexpected behavior But note that this feature is still experimental and has not been tested across platforms due to lack of funds The setup of the persistent database backing is definitely more tricky than the other Renew options but it is supported by some predefined scripts The source package contains among others the SQL script initTable sql which can be found in Simulator src de renew database entitylayer It creates the required database tables for an Oracle server For other databases the script will need some changes but even the various versions of Oracle differ enough to cause minor problems A database backend which supports transactions is required
38. is provided by the Simulator plug in simulation controls a running simulation without using the graphical editor Use one of the subcommands help run step stop or term as argument See Section This command is provided by the Simulator plug in setFormalism chooses the formalism given as argument as current formalism This is equiva lent to selecting a formalism in the menu see Section 4 4 6 This command is provided by the Formalism plug in listFormalisms lists all installed formalisms The names listed by this command can be used as argument to the setFormalism command or as value for the renew compiler property This command is provided by the Formalism plug in keepalive displays and manipulates the keep alive feature of the prompt plug in see Sec tion 75 guiprompt opens a graphical prompt dialog see Section 2 7 5 if the Gui Prompt plug in is installed 2 7 5 Prompt The prompt plug in is part of the base distribution It enhances the plug in system by an interactive command shell in the Java console window The editing features are limited but it allows to issue commands to the plug in system at runtime If you start the renew from a shell you will be presented with the prompt Enter command at the Java console Here you can enter any of the commands mentioned in the previous subsection The prompt plug in itself offers one command with two alternative arguments keepalive on enables the keep alive feature As long
39. it is a Inscription it is used for the simulation see Section 4 3 3 The Inscription Tool A Name text type does not change the simulation but makes the log more readable see Section 4 3 3 The Name Tool A It is quite convenient to switch off certain inscriptions by converting them to labels Y if you suspect them causing some problems This way you can easily re activate them by converting them back to inscriptions You might also want to have certain inscriptions appear as transition names during the simulation You can achieve this by duplicating the inscription figure dragging the duplicate to the transition see Section The Connected Text Tool and changing the duplicate s text type to Name 4 4 5 Net This menu offers commands that are useful for nets only You can semantically modify figures in a drawing check the active drawing for problems or configure the graphical simulation feedback for net elements Split transition place This command provides a simple way to refine net elements by splitting a single transition or place into two 92 If a transition is split the old transition is connected to a newly created place This place in turn is connected to a newly created transition The inbound arcs of the old transition remain unchanged the outbound arcs are reconnected to the new transition Reserve arcs are split into an inbound and an outbound arc which are handled respectively If a place is split it w
40. modulo number plus number String minus number lt lt shift left integral gt gt shift right integral gt gt gt signed shift right integral lt less than number gt greater than number lt less than or equal number gt greater than or equal number equal primitive reference unequal primitive reference amp and primitive 7 exclusive or primitive or primitive Table 3 2 Java binary operators rules separate operators of equal precedence negate number bit complement integral not boolean Table 3 3 Java unary operators explicit cast E g byte bi b2 adds the two bytes b1 and b2 and truncates the result to 8 bits You might also want to reduce the precision of a floating point number by saying float d1 where d1 is a double variable The opposite case where precision is added e g long b1 is helpful too but usually this kind of conversion is added automatically in the places where it is needed Casts between reference types are also possible but here no conversion takes place In stead it is checked that the operand is indeed of the given reference type either at compile time or at run time if required E g if a variable o of type Object is declared we can say String o to ensure that o does indeed hold an object of type String There are a few unary operators too They are listed in Table 3 3 Unary operators and casts have a higher operator precedence than any binary operator
41. of all drawing and editing capabilities Renew offers 4 1 Mouse handling Most current computer platforms use a mouse with at least two mouse buttons Whenever this manual instructs you to do mouse operations you should use the left mouse button You should use the right mouse button only when it is especially indicated to do so If your mouse has three or more buttons the excess buttons usually behave like the right mouse button Your operating system might support a special option to switch the two mouse button so that left handers can operate the device more easily This will also switch the meanings of the mouse buttons within Renew Older Apple Macintosh mice have got one mouse button only In this case you can press and hold the Apple key while clicking the single mouse button whenever this manual commands you to press the right mouse button On other operating systems too you might be able to use a single button mouse by pressing some control key whenever you need access to the right mouse button In all cases you can substitute right mouse clicks by appropriate menu commands or tool selections but the right mouse button greatly adds to drawing speed Some mouse operations react to a simultaneously held down shift or control key These operations alter their behavior slightly as long as the modifier key is pressed For example a resize operation can be restricted to obtain square dimensions as long as the control key is pressed
42. of the output of JavaCC D 1 4 Bill s Java Grammar A Java grammar billsJava1 0 2 jj was distributed together with JavaCC 0 7 as a sample grammar Bill McKeeman mckeemantmathworks com contributed this grammar to JavaCC The relevant license information from Sun states 2 SAMPLE GRAMMARS You may modify the sample grammars included in the Software to develop deriva tives thereof Sample Grammar Derivatives and sublicense the Sample Gram mar Derivatives directly or indirectly to your customers 4 YOUR INDEMNIFICATION OF SAMPLE GRAMMARS DERIVATIVES AND DEVELOPED PRODUCTS You agree to indemnify hold harmless and defend Sun from and against any claims or suits including attorneys fees which arise or result from any use or distribution of Sample Grammar Derivatives and or Developed Programs The original parts of billsJava1 0 2 jj which are now contained in a modified form in the files JavaNetParser jj FSNetParser jj FSParser jj and StubParser jj are Copy right C 1996 1997 Sun Microsystems Inc A sublicense for these grammars is hereby granted If you have any further questions please consult the file COPYRIGHT as distributed with JavaCC D 1 5 Graph Layout Algorithm The graph layout algorithm used in the class de renew util GraphLayout was originally provided by Sun as part of the Java Development Kit The relevant license information from Sun states Sun grants you Licensee a non exclusive royalty
43. of their tops middles bottoms or borders Diagonal This command spreads the figures in both directions horizontally and vertically All figures are treated with respect to their center point First of all a virtual line is drawn from the outermost figure in relation to the center of the bounding box of all selected figures to the figure most apart from the outermost one Afterward all other figures are moved onto that line with equal distances between their center points The order of the figures on the line is determined by the order of the orthogonal projections of their original location onto the virtual line 87 Figure size These two commands set the size of figures The function copy within selection sets the size of all selected figures to the size of the figure that was selected first The command reset to default resets the selected figure s sizes to their figure type specific default As there are defaults specified only for net element figures the command will not have any effect on ordinary drawing figures Send to Back Bring to Front The figures in a drawing have a so called Z order that determines the sequence in which the figures are drawn If a figure is drawn early other figures may cover it partially or totally To change the Z order of figures the functions Send to Back and Bring to Front are available Send to Back puts the selected figure s at the beginning of the figure list and Bring to Front puts it them at
44. points within the figure Using these handles a figure can be manipulated The different types of handles are discussed in Section 4 3 2 in the subsection of the corresponding figure s tool To move a single figure it is crucial not to hit a figure s handle otherwise the handle s function is invoked instead of moving the figure s When more than one figure is selected the handles of all selected figures are shown but have no effect To actually use the handles you have to select exactly one figure The easiest way to do so is to click on an empty spot in the drawing and then select the figure you want to manipulate In Table 4 1 we summarize the actions of the inspection and direct manipulation functions for all figures The actions associated to the different figures are explained in more detail in the section that documents the corresponding tool Some of the entries in the table refer to the simulation mode which will be explained in more detail in Section 4 4 6 4 3 2 Drawing Tools Renew provides several drawing tools which create and manipulate drawing figures These drawing figures do not have any semantic meaning to the net simulator but may be used 70 type of figure rectangle ellipse text connected text transition place virtual place arc declaration inscription name label transition instance place instance cardinality marking token marking double click select children select select parent
45. prompt capabilities Since release 2 2 it also provides Finder integration for Renew drawing files 2 5 2 Unix We supply a simple install script at renew2 4 3 bin unix installrenew that will handle the installation on most flavors of Unix Run that script with cd renew2 4 3 bin unix sh installrenew and it will create the shell scripts renew loadrenew compilestub makestub and jcompile in the same directory see Table 2 1 However you must make sure that java can be called with your current setting of the PATH environment variable It is also required that you start the installation script from the bin unix directory otherwise it cannot find the location of the package Renew We distribute some files to support desktop integration in FreeDesktop based envi 2 2 ronments like Gnome In the directory renew2 4 3 bin unix freedesktop there is a README file that explains how such desktop integration can be achieved How ever desktop integration still requires a manual configuration process Renew With release 2 4 there is an installdesktop and an uninstalldesktop script 2 4 to automatically install and uninstall the desktop integration in the FreeDesktop environment We also provide deb packages for Debian based distributions Just add the following lines to your etc apt sources list The Renew Repository deb http www informatik uni hamburg de TGI renew debian renew stable Download the public key for the Renew reposito
46. sequence of numbers The first number of the sequence determines the length in pixels of the first dash The second number is 90 interpreted as the length of the gap after the first dash The third number determines the second dash s length then the next gap s length follows and so on The sequence must consist of an even number of numbers There is only one exception A single number can be used for a simple dashed line where dashes and gaps are of the same length The normal solid line style can be set by applying an empty sequence Some examples from our predefined line styles dashed 10 S medium dashed 15 10 nn dash dotted 7313 a A Renew Line styles can not only be applied to lines connections and scribble figures but 2 also to rectangles ellipses polygons transitions places and other closed shapes Line Shape With this attribute a straight line can be changed to a B Spline and vice versa Every linetype can be changed to a B spline But these lines retain their other like handles and behavior If this conversion is applied there are more attributes offered to influence the bspline algorithm standard This works as a reset to standard settings with a degree of 2 and a segment size of 15 Segments This is used to change the number of segments to smooth the edges Degree The lower the number the closer the line sticks to the handles 2 creates maximally curved line The degree depends on the number of
47. source distribution consumes about 18 MByte Compiling the source will additionally generate 5 MByte of executables for the main distribution and the compilation of all available plugins will consume another 30 MByte for additional libraries and executables The full JavaDoc will occupy between 45 and 57 MByte 2 4 1 Base Installation In the following we assume Unix filename conventions i e directories separated by slash For other operating systems you might need to change it to backslash Also the list separation character differs In Unix based environments is used while in DOS based environments the is reserved for drive letters so is used for lists Extract the base distribution to a directory of your choice A directory renew2 4 3 will be created in the current directory Documentation files for example this manual are placed in the subdirectory renew2 4 3 doc The subdirectory renew2 4 3 samples contains example nets The functionality of Renew has been decomposed into several plug ins which reside as jar files in the subdirectory renew2 4 3 plugins This is also the place where you can add extra plug ins see Section 2 7 The file renew2 4 3 loader jar is a jar file that could be used to execute Renew e g by saying java jar some where renew2 4 3 loader jar gui if you extracted the zip file into some where In a DOS based environment this would look something like java jar C some where renew2 4 3 load
48. the button is re leased all figures that are completely inside the rectangle area are selected Combining this with the Add to Selection function is possible Inspection Some figures have an additional inspect function that is invoked by double clicking them which displays some additional information of the figure without modi fying it E g all connected text figures see Section 1 3 2 The Connected Text Tool select their parent during inspection Direct Modification Some figures have an additional direct manipulation function that is invoked by clicking on them with the right mouse button E g all text figures switch into edit mode Dragging If the mouse button is depressed inside a figure and held down the drag mode is activated All figures that are currently selected are moved until the mouse button is released An advanced feature of dragging is that it is possible to change a figure s parent For more information on this function see Section 1 3 2 The Connected Text Tool Stepwise Movement You can use the cursor movement keys on the keyboard to move selected figures upward downward leftward or rightward in steps of one pixel If no figure is selected the cursor keys scroll the viewable area of the drawing in its window Renew By holding the shift key during cursor movement selected figures are moved in steps of 10 pixels Manipulating Depending on the kind of selected figure handles are displayed at special
49. the current simulation 2 1 In previous Renew releases the trace has always been printed to the console now you can closely inspect the trace inside the editor The shortcut for this command is Ctrl1 L By default the drop down list on top of the window provides one simulation trace that covers the last 20 simulation steps You can configure additional traces of different length that focus on specific net instances places or transitions using the Logging tab of the Configure simulation dialog see above A double left mouse button click on a simulation trace entry opens a window that displays the whole message using multiple lines if appropriate A right mouse button click opens a context menu that allows you to display the net template or instance that was involved in the simulation step Renew Jt is also possible to select the individual place or transition in the net template or 2 2 instance y The mouse actions to inspect a trace entry are not available before you have selected SY any line of the simulation step it belongs to Formalisms Renew This submenu configures the current formalism used during compilation and simu 2 0 lation Please note that a running simulation will always stay with the formalism it has been started with To apply the chosen formalism to the simulation you have to terminate it and start a new one The entries of this menu depend on the set of plug ins currently installed The basic renew distrib
50. the end with the result explained above i A Sometimes certain figures can not be reached to select and modify them Using Y these functions it is possible to temporarily move the covering figure to the back select the desired figures and move the figure to the front again Another option in cases like this one is to use Area Selection see Section 4 3 1 Automatic Net Layout Especially for automatically generated nets it is nice to have an automatic layout of the net graph so that one gets at least a rough overview of the structure of the net This menu entry start an automatic net layout on the current drawing While this mode is active the nodes of the net are moved according to certain rules that are to some extend inspired by physical forces acting on a mesh of springs e Arcs have a certain optimal length that is dependent on the size of the adjacent nodes They will act as springs e Arcs feel a torque whenever they are not horizontally or vertically oriented The torque works toward these optimal positions e Nodes feel a repulsive force from each other until a certain distance is reached where this force disappears entirely e Nodes feel friction i e the motion that was caused by the forces mentioned before continually slows down unless the force is still applied and compensates the friction e Nodes that would move out of the upper or left border are pushed back into the viewable area of the drawing These rul
51. the user moves them By fixing the location of some nodes you can select a preferred direction or specify the basic shape of the net while leaving the details to the layout algorithm 4 4 4 Attributes This menu helps you to change a figure s attributes after its creation If several figures are selected the attribute is changed for all figures that support that attribute If you try to change an attribute that some selected figures do not support e g font size for rectangles nothing is changed for that figures but the change is still applied to the other figures Fill Color The fill color attribute determines the color of the inner area of a figure All figures but the line based figures like connection arc etc offer this attribute The values for this attribute could be any RGB color but the user interface only offers 14 predefined colors from which you can choose The default fill color is Aquamarine except for text figures where it is None Renew When you choose other at the end of the list of colors you get a full featured 2 1 color chooser dialog that provides multiple ways to define any color There are four buttons at the bottom of the dialog Apply applies the currently chosen color to selected figures Update chooses the color of a selected figure and makes it the current color in the dialog OK closes the dialog and applies the currently chosen color to selected figures Cancel closes the dialog 89 Ly The dial
52. the various places Virtual place copies depicted by doubly lined circles on the right hand side are arranged according to the used topology so that the topology becomes immediately obvious Of course it is now harder to try different topologies but this kind of visualization is quite effective in classroom demonstrations 3 10 2 Clear Arcs Clear arcs are used to remove all tokens from a place They are typically applied to reset the state of the net to a well defined marking I3 gives some thoughts on clear arcs and on many other arc types In order to use this arc type you need to select the extended sequential mode as described in Subsection 2 6 5 A clear arc is indicated by a double arrow tip attached to the transition s end of the arc where the arrow tip is hollow i e filled with the background color It need not be inscribed If it is inscribed it must be inscribed with a single variable that is either untyped or that has an array type In the latter case all the tokens in the place are put into an array and the variable is bound to the array Note that the binding occurs only during the firing i e as though the variable was assigned in an action statement Hence you cannot use the variable of a clear arc for other input arc inscriptions or for guards However you can use the variable for output arcs This is very useful in conjunction with a flexible output arc when you want to move all tokens from one place to another
53. type E g it offers the possibility to select all transitions or all arcs or all inscriptions that are attached to places This command comes in handy when you want to set attributes like color or font size for all figures of a certain type Add To Selection This command is similar to the select command but it does not clear the selection before it selects the net elements thereby achieving a union of the selection sets This command is especially useful when you want to select a combination of net elements that is naturally covered by the selection command itself E g you can select all transitions and then add all inscriptions of transitions to the selection Remove From Selection This command is the opposite of the add to selection command It removes certain figures from the selection but leaves the selection state of the remaining figures unchanged This command can be used to select all figures but not the transitions or not the arcs Restrict Selection Sometimes you want to select a certain type of net elements inside a certain area In this case the restrict command allows you to select the entire area as described in Subsection 4 3 1 but to restrict the selection to a certain type of figures afterward The remove from selection command can be used instead of this command if you want to specify the figures to drop from the selection instead of the figures to keep in the selection 4 4 3 Layout The Layout menu allow
54. unfortunately this does not work on all Unix platforms Then create a new inscription by right clicking the net element Edit the new inscription by right clicking it and paste the copied text by pressing Ctrl V a r Duplicate Duplicate works like Copy followed by Paste see previous Section where the paste coordi nates are not depending on the last mouse click but are just a small offset to the right and down from the position of the original selection The keyboard shortcut for Duplicate is Ctrl D Delete Removes the selected figures from the active drawing Note that if a figure is removed all its connected text figures and connection figures are also deleted The keyboard shortcut for Delete is the backspace and or the delete key depending on the platform Search Search amp Replace Search looks for a match or substring match of an user given search string in all textfields of all loaded nets Search is case sensitive After an occurrence of the search string is found the next can be found by pressing the search button again Changes on the search string start a new search The keyboard shortcut for this function is Ctr1 F Search amp Replace gives the opportunity to replace any found search string with a replace string Each replacement is prompted and has to be confirmed by the user Changes on the replace string start a new search The keyboard shortcut for this function is Ctrl G Renew Since 2 3 the se
55. value of an attribute happens to be an object that already appeared in the open part of the object graph only the temporary name number of that object is display as the attribute s value To help you find the original object you can click on this object number and all appearances of this object are highlighted by a red frame To get rid of the highlighting just click on any of the numbers again Figure 4 4 shows an example of a java awt MenuBar object that is being browser as an Expanded Token In the example the menu bar contains one menu File with two menu item of which the first one is Load The parent of the first menu item is again the menu as you can see by the highlighting The second menu item is closed Renew tries to find attributes of the token object by using Java s reflection mechanism on fields and get methods Any method without parameters and with a return type which is not void is regarded a get method In some cases such methods return volatile changing results but are only queried once when the token figure is expanded This means you should not expect to see changes of a token object while browsing it Renew stores for each place the preferred display mode chosen by the Marking menu This means that every new simulation starts with the display mode chosen for each place and the display mode is also saved to disk The menu can also be used to change the display mode during run time To do this either the token figure
56. want to change the text contents of an existing text figure just make sure the text tool is activated and click on the text figure The text editor described above will appear Again confirm your changes by clicking somewhere outside the editing area er A fast way to enter text edit mode for any text figure including connected text Y inscription name and declaration figures is to right click on these figures The corresponding tool is activated and the figure is put into text edit mode immediately The Connected Text Tool Connected text works exactly like normal text except that it is connected to some other figure which is called its parent To create a connected text figure select the connected text tool and click on the figure that is to become the parent of the new connected text figure If you select a figure that cannot take a connected text figure or if you select no figure at all your selection is ignored If the figure was successfully chosen continue with editing text like with a normal text figure see above Now every time you move the parent figure the connected text figure will move with it Only when you drag the connected text figure itself the offset to its parent is changed To verify which figure is the parent of some connected text figure double click on the connected text figure and the parent if there is any is selected A special feature of connected text is dragging a single connected text figure or any
57. will interpret paths with it as two arguments 2 6 Special Configuration Options There are several options that can help to adapt Renew to your specific needs Usually you should not need to use these options so it is best to skip this section on the first reading 2 6 1 Ways of configuring Renew Renew There are at least two ways to configure any of the options mentioned in the following 2 0 sections In Java terminology an option is configured by setting a property to a value At startup You can supply property values on the Java command line with the D option when you start Renew this is the way you could configure previous Renew releases For example to configure that Renew uses a sequential simulator instead of the default concurrent one you can set the property de renew simulatorMode to the value 1 This is done by starting Renew with the command line java Dde renew simulatorMode 1 jar loader jar gui It is important that you do not insert any spaces between the D option the property the sign and the value Also property names are case sensitive This way you can configure any property for just one run of Renew However you lose the simplicity provided by the platform dependent startup scripts You will have to enter the Java command line directly including the full path to loader jar and the initial command gui for the loader Permanently Renew To configure properties permanently create or edit either t
58. with place capacities test arcs and inhibitor arcs In M Ajmone Marsan editor Application and Theory of Petri Nets 1993 Proceedings 14th International Conference Chicago Illinois USA volume 691 of Lecture Notes in Computer Science pages 186 205 Springer Verlag 1993 Available at http www daimi au dk sorenchr publ html Eindhoven University of Technology Woflan The Workflow Analyser 1998 WWW page at http www win tue nl woflan Erich Gamma JHotDraw 1998 Available at http members pingnet ch gamma JHD 5 1 zip Olaf Kummer Simulating synchronous channels and net instances In J Desel P Kem per E Kindler and A Oberweis editors 5 Workshop Algorithmen und Werkzeuge f r Petrinetze pages 73 78 Forschungsbericht 694 Universitat Dortmund Fachbereich Informatik October 1998 Olaf Kummer Tight integration of Java and Petri nets In J Desel and A Ober weis editors 6 Workshop Algorithmen und Werkzeuge ftir Petrinetze pages 30 35 J W Goethe Universit t Institut f r Wirtschaftinformatik Frankfurt am Main Fach bereich Informatik October 1999 114 11 Olaf Kummer Referenznetze Logos Verlag Berlin 2002 12 Laboratoire d Informatique de Paris 6 Macao Graph Editor Framework 1998 13 14 15 16 17 18 19 WWW page at http move 1ip6 fr software MACAO Charles A Lakos and S ren Christensen A general systematic approach to a
59. 6 is now required for compiling and running Renew Renew now includes and uses the 2 2 version of the FreeHEP project for graphical exports of drawings Renew offers a better syntax check for Java reference net models If a Java inscription references a non existing method or field of an object a proposal for existing methods or fields is made instead of just pointing out the syntax error see also Section 1 7 Minor modifications to the graphical editor functionality of Renew consist of the following The names and colors of place figures are now transferred to their virtual places The editor prevents adding more than one arc inscription by right clicking on an arc with the mouse as this happened rather by accident than on purpose However it is still possible to add multiple arc inscriptions by using the inscription tool Additions On startup Renew displays a splashscreen that gives information about the loaded plugins There are two new entries in the File menu The first addition is a list of recently saved drawings The second addition is the possibility to open the Renew Navigator which allows to import file folders and show their content in a tree view A more detailed description of how to use the navigator can be found in Section 4 4 1 It is now possible to define re usable Net Components A net component consists of a set of net elements that typically fulfill some generic function and can be treated as a whole in a larger net mod
60. List The second part of the menu allows you to view all breakpoints locate the associated net elements and possibly reset individual breakpoints Save simulation state This menu entry saves the current simulation state to a file so it can be restored later on by the menu command Load simulation state The saved state also includes all net instances currently opened in drawings and all compiled nets The default extension for Renew simulator state files is rst Points to be aware of e Saved simulation states will most likely not be compatible between different versions of Renew e All custom classes used in the current marking of the net must implement the interface java io Serializable in a sensible way to obtain a complete state file There are also some minor side effects e This command halts the simulator because there must not occur any changes to the current simulation state while it is saved to obtain a consistent state file You can continue the simulation afterward e The binding selection window will be closed if it is open Load simulation state This menu entry loads a simulation state from a file saved by the menu command Save simulation state before You will then be able to continue the simulation as usual from the point at which the simulation state was saved If all drawings used in the state are loaded you can use all simulation control facilities as usual However it is not necessary to have all used
61. NTIFIER gt This gives at least a hint where the syntax error originated and which context the parser expected In our case the inscription a do was reported because do is a keyword that must not be used as a channel name 4 7 2 Early Error Messages These errors are determined during the immediate syntax check following each text edit Bad method call or no such method Typically you entered two pairs of parentheses instead of one Possibly a class name was mistaken for a method call Maybe a name was misspelled Boolean expression expected An expression following the keyword guard must be boolean Maybe you wrote guard x y but meant guard x y Cannot cast An explicit cast was requested but this cast is forbidden by the Java typing rules Renew determined at compile time that this cast can never succeed Cannot convert The Java type system does not support a conversion that would be necessary at this point of the statement Cannot make static call to instance method An instance method cannot be accessed statically via the class name A concrete reference must be provided Maybe the wrong method was called Enumerable type expected The operator requested at the point of the error can act only on enumerable types but not on floating point numbers Expression of net instance type expected For a downlink expression the expression before the colon must denote a net instance E g it is an error if in x ch the vari
62. Renew User Guide Olaf Kummer Frank Wienberg Michael Duvigneau Lawrence Cabac University of Hamburg Department for Informatics Theoretical Foundations Group Release 2 4 3 September 11 2015 This manual is 2015 by Olaf Kummer Frank Wienberg Michael Duvigneau Lawrence Cabac Arbeitsbereich TGI Renew Fachbereich Informatik Universitat Hamburg Vogt K lln StraBe 30 D 22527 Hamburg Germany Apple is a registered trademark of Apple Computer Inc Alphaworks is a registered trademark of IBM Corporation IBM is a registered trademark of IBM Corporation Java is a registered trademark of Oracle Corporation JavaCC is a trademark of Oracle Corporation IATEX is a trademark of Addison Wesley Publishing Company Macintosh is a registered trademark of Apple Computer Inc Mac OS X is a trademark of Apple Computer Inc Microsoft Office is a registered trademark of Microsoft Corporation MySQL is a trademark of Oracle Corporation Oracle is a registered trademark of Oracle Corporation PostScript is a registered trademark of Adobe Systems Inc Solaris is a registered trademark of Oracle Corporation OpenOffice is a trademark of The Apache Software Foundation Stufflt is a trademark of Aladdin Systems Inc Sun is a registered trademark of Oracle Corporation TEX is a trademark of the American Mathematical Society UML is a trademark of the Object Management Group Unicode is a registered trademark of Unicode Inc
63. Renew does not provide an automatic net loading mechanism that would correspond to class loading in Java In Fig 3 19 you can see the net customer that describes a customer accessing a bank account A new account is created money is deposited and the customer checks the current savings 53 If you load the two nets from the directory samples call and start the simulation of net customer you will see that the firings of the transitions are no longer sequential E g we have in the simulation log file Synchronously Removing in customer 0 created Testing account 2 in customer 0 account Firing customer 0 deposit Synchronously Removing int 0 in account 2 money Firing account 2 deposit Putting int 500 into account 2 money Untesting account 2 in customer 0 account Putting into customer 0 deposited The transition deposit of customer fires at step 3 but at first it can only remove its input token and test the account reference The output token is not put into the place deposited before the action inscription is completed This requires the invocation of the method acc deposit 500 Because this method must perform a synchronization it cannot complete immediately First the method requests a synchronization with transition deposit of net account in step 4 After that step the method returns the action is completed and a token appears in place deposited Note how the individual steps are mixed wi
64. Sequential mode in the Configure Simulation dialog see Section 4 4 6 and restart the simulation Renew Please note that the sequential mode does no longer use the SequentialSimulator 2 0 class but the NonConcurrentSimulator class The latter is not able to detect deadlocks and will not terminate the simulation automatically The change became necessary because the simulator plug in now allows to relive dead simulations at any time by creating new net instances 19 2 6 6 Class Loading and Reloading When you are developing an application that consists of Java code and net drawings or if you want to extend some Renew plug in by supplying custom Java classes then you need to make your classes known to Renew The Java way of doing this is to add your classes to the Java classpath either by setting the environment variable CLASSPATH or by providing an appropriate classpath option to the java command Renew With the new plug in system see Section 2 7 providing custom classes via the Java 2 0 classpath option or variable has some issues First our suggested startup command line uses the jar option which simply overrides any supplied classpath see the Java tool documentation for details Second the plug in system uses its own class loader to find plug ins Due to the Java class loader concept the plug in class loader hides all plug in classes from any class that is loaded via the system classpath This means that Renew can load an
65. Step This menu performs the next simulation step in the active simulation run or starts a new simulation run if there is no active simulation If a simulation is already running in continuous mode one more step is executed and then the simulation is paused to be continued in single step mode Thus it is possible to switch between continuous and single step simulation modes The keyboard shortcut for this function is Ctrl I Simulation Net Step Renew This menu entry performs a series of simulation steps in the active simulation run 2 1 or starts a new simulation run if there is no active simulation The simulation is paused when an event in the net instance in the current instance window occurs Renew The keyboard shortcut for this function changed and is now Ctrl Shift I 2 3 Halt Simulation This menu halts the current simulation run which has been started with Run Simulation or terminates the search for a possible binding in single step mode No further simulation steps are made but you are free to resume the simulation with Run Simulation or Simulation Step y There are situations where a net invokes a Java method that does not terminate In these cases Renew cannot succeed in halting the simulation The keyboard shortcut for this function is Ctr1 H Renew Qn Mac OS X systems Cmd H is bound system wide to hide the application window 2 1 Therefore the shortcut key has been changed to Shift Cmd H Terminate Simulation
66. The simulation engine was restructured The GUI application classes were restructured and partly converted to use the Swing package from the Java foundation classes The import and export menus have been restructured The handling of the various configuration properties has been canonised by the plug in system The class loader for custom classes has changed The net channel is no longer invoked implicitly on instance creation The class SequentialSimulator is replaced by the NonConcurrentSimulator without deadlock de tection feature The expanded token display feature has moved into the optional fs plug in this option has no effect unless the fs plug in is installed Additions A plug in system was added as bottom layer of the application The ability to switch simulator modes net formalisms the net loader path and the remote access feature on the fly was added A PNML compatible export format was added The editor is able to load drawings from URLs The net loader can now search nets relative to the classpath 2 9 10 Changes in Version 2 0 1 Modifications This was a maintenance release that provided bug fixes for the install scripts and some redraw issues of the graphical net editor Additions An experimental AppleUI plug in is available as optional download It provides rudimentary integration with the MacOS look amp feel 2 9 11 Changes in Version 2 1 Modifications Many error messages of the Java net compiler or about probl
67. UNIX is a registered trademark of AT amp T Windows is a registered trademark of Microsoft Corporation X Windows System is a trademark of X Consortium Inc The trademarks may be claimed in one or more countries Other trademarks are trademarks of their respective owners The use of such trademarks does not indicate that they can be freely used Please refer to the license section of the Renew user guide for more information about copyright and liability issues This document was prepared using the IAT X typesetting system This document is contained in the files doc renew ps and doc renew pdf as distributed together with Renew 2 4 3 Contents e de ot ie y ads eee Ei is A od eo dado ao AS A eae hee ee ee ee oe Ee hye ah See eras Sead eg eas Moke didedye te 8 4 4 ood eh a eet Te eee ee eee da iia ee ba dl e 4 e bd Bae dais die ocio dd ee Ser ee rifas des seed 2 4 1 Base Installatiodl a a riada e a ea FAA IIS A PA A ee E E E A isa ka a oe ee es as A 2 6 1 Ways of configuring Renedo AAA E O ds Phd are E a a pod a ica da a Be ba oe a OOS ata a ow ia db dd 2 6 6 Class Loading and Reloading 2 9 1 Changes in Version 1 1 0 a 29 2 9 2 Changes in Version 1 9 0000000 0 ee ee 30 2 9 3 Changes in Version 1 3 30 ea a aaa 31 2 9 6 Changes in Version 1 5 1 31 2 9 7_ Changes
68. able timed simulations two options need to be configured The usual Java 2 0 compiler complains about time inscriptions you have to choose the Timed Java Compiler in the Formalisms menu see section 4 4 6 or with the setFormalism command see section 2 7 4 Timed nets can only be simulated in the sequential 62 x Math random lt 0 2 import de renew util Dist ship next waiting for counter x ship ship arrived unloading required customs 1 OO cintas AR 1 x 1 Dist Xx e x true e X x 5 negexp 2 waiting no unloading check check required X start xoDist B ynioeding pos es et pe negexp 6 1 unloading crane O 0 0 Ww mn Officers checked chief officer x 10 0 x i e HAD gt gt 9 load ship empty ship finish unloading goods on truck truck departs delivered goods Figure 3 29 The net port simulation mode as described in subsection 2 6 5 For your convenience the sequen tial simulation mode is enabled automatically when you choose the Timed Java Compiler in the editor In timed mode a time stamp is attached to each token It denotes the time when the token becomes available Delays may be used with arcs in order to control the time stamps of token and the firing times of transitions A delay is added to an arc by adding to the arc inscription the symbol and an expression that evaluates to the number of time units E g x 1 t indicates that the token value x 1 has to be move after t time units Input ar
69. able x is of type String Maybe you have to use a cast Expression of type void not allowed here An expression of void type was encountered in the middle of an expression where its result is supposed to be processed further e g by an operator or as an argument to a method call Maybe you called the wrong method 108 Integral type expected The operator requested at the point of the error can act only on integral types but not on floating point numbers or booleans Invalid left hand side of assignment In an action inscription only variables fields and array elements can occur on the left hand side of an equation Maybe this expression should not be an action Multiple constructors match A constructor call was specified but from the types of the arguments it is not clear which constructor is supposed to be called There are overloaded constructors but none of them seems to be better suited than the others Maybe you should use casts to indicate the intended constructor Multiple methods match A method call was specified but from the types of the arguments it is not clear which method is supposed to be called There are overloaded methods but none of them seems to be better suited than the others Maybe you should use casts to indicate the intended method No such class The compiler could not find a class that matches a given class name but it is quite sure that a class name has to occur here Maybe you misspelled the class na
70. achine where the server will be running This is a program distributed together with Java that stores RMI objects and makes them accessible to other VMs Simply run the program rmiregistry e g as a background task Note that the rmiregistry process either needs a classpath with renew2 4 3 plugins remote 2 4 31 0 jar included or that the simulation server has to be configured with the java rmi server codebase property see Java RMI docs for details Property name Type Comment de renew remote enable boolean Enables remote access defaults to false de renew remote publicName string Name to use for RMI registration de faults to default de renew remote serverClass class Implementation of the interface de renew remote Server defaults to de renew remote ServerImp1 de renew remote socketFactory class Implementation of the interface java rmi server RMISocketFactory defaults to RMI s default factory Table 2 3 Properties to configure a remote simulation The remote simulation can be configured by using the properties listed in Table 2 3 The defaults are suitable for most cases so you just need to enable the remote access by setting the property de renew remote enable to true The publicName property is required if you intent to run several servers on one machine When connecting from an editor you can specify the server to connect to by its name The serverClass and socketFactory properties are normally not needed Plug in devel
71. ameter string a All Java methods can be used in reference nets but there are some critical points First of all methods can be evaluated more than once Worse a method might be invoked even though the transition does not fire This is done because the result of a method invocation might be needed to determine whether a transition is enabled at all Therefore it is best if the invoked methods do not produce any side effects If side effects are required then they should be invoked in action inscriptions only Fig 3 7 shows some example method calls that are invoked by net inscriptions The net is saved in the directory samples simple The declaration node contains an import statement that instructs the simulator to search the package java awt for classes whose names appear in the net The variables f and b are then declared as a Frame and a Button These two classes are in the package java awt so we could have written java awt Frame and java awt Button instead The procedure that has been implemented here is simple A window and a button are created the window is resized and the button is added to the window Now we can show the window let the user click it some times and remove it from the screen again It is possible to give multiple actions in a single transition inscription in a semicolon separated list e g action y 0 m x action x o m would be allowed Note that the order of execution need not match the textual order In the pre
72. and specialized classes that implement some useful topologies like RingTopology StarTopology or LineTopology If further topologies are needed new classes can easily be added say for hypercubes or meshes The net from Fig B 25 shows a simple algorithm that determines a global leader within a network of processors that can only communicate locally The green net elements constitute the core algorithm as presented in 17 Additional yellow net elements care for the initializa tion process You can see the colors when you load the net from its directory samples reisig In your nets too the use of color might improve the nets presentation 59 import samples reisig x y x y t prod t neighbors x y pending x y x y xz guard z lt y x z guard z gt y Figure 3 25 The net election In this example a star topology is used By default a star topology is directed but in this case we add the inverse to the original topology so that a symmetric topology arises Flexible arcs are used to send messages to all neighboring arcs whenever a possible new leader has to be announced Fig 5 26 shows the same net but augmented by a visualization component For every node of the communication network there is a place that is marked with the node of best currently known priority Transitions with synchronous channels which are located in the lower part of the drawing are used to sort the information into
73. arch window allows you to select whether the search should be case 2 sensitive and whether the search shall include all drawings or only the active one Group Ungroup You can create a group of all currently selected figures in the active drawing A group is actually a new figure which consists of all the selected figures You can even group a single figure which does not really makes sense unless you want to prevent resizing of this figure From now on the figures inside the group can only be moved deleted etc together until 85 you ungroup the group of figures again To release a group one or more groups have to be selected Then select the Ungroup menu and all group participants are single figures again which are all selected Select All Commands that allow selection or deselection of large sets of nodes allow the user to select groups of logically related net elements together For selecting locally related net elements or individual net elements see Subsection 4 3 1 Using the select all command all figures of a drawing are selected This is useful when you want to move all the net elements to a different place This command works even for figures that are located off screen Invert Selection Inverts the selection of the drawing All selected net elements will be removed from the selection whereas all the other net elements will be selected Select This menu hierarchy is used to select all nodes of a certain
74. ariables Worse if a method is overloaded the choice of the actual method must be delayed until runtime when all operator types are known This is contrary to ordinary Java where overloaded methods are disambiguated at compile time Fig 3 5 shows a typed variation of the greatest common divisor algorithm First you can see the type inscriptions of the places that are all int in this case Second you will notice the declaration node where the two variables are declared As in Java declarations consist of the type followed by the name of the variable Places can be typed too This allows the simulator to catch some difficult situations before the actual simulation For input arcs the type of the arc inscription should be comparable to the type of the place i e either a subtype or a supertype Otherwise it is probable that the expression yields a value that cannot be a token in the place Note that for this type check we have to use the lossless conversion rules as depicted in Figure 3 3 For output arcs we require that the type of the arc expression is narrower than the type of the place so that the place can always take the resulting token This is important because the values of the output expressions might only be determined during the firing of the transition when it is too late to declare the transition disabled For input arcs we can simply ignore any binding that would result in a token of a bad type As a special case it is required t
75. arious freeware libraries namely Mark Donszelmann Erich Gamma Doug Lea David Megginson Bill McKeeman and Sriram Sankar Dr Maryam Purvis Dr Da Deng and Selena Lemalu from the Department of Informa tion Science http divcom otago ac nz infosci University of Otago Dunedin New Zealand kindly aided us in the translation of parts of the documentation and are involved in an interesting application project Valuable contributions and suggestions were made by students at the University of Ham burg most notably Hannes Ahrens Tobias Betz Lars Braubach Timo Carl Dominic Dib bern Friedrich Delgado Friedrichs Matthias Ernst Daniel Friehe Olaf Grofler Julia Hage meister Sven Heitsch Marcin Hewelt Thomas Jacob Andreas Kanzlers Lutz Kirsten Michael K hler Till Kothe Annette Laue Matthias Liedtke Marcel Martens Klaus Mitrei ter Eva M ller Jens Norgall Sven Offermann Martin Pfeiffer Alexander Pokahr Tobias Rathjen Heiko R lke Benjamin Schleinzer Jan Schl ter Marc Schonberg J rn Schumacher Volker Tell Benjamin Teuber Matthias Wester Ebbinghaus and Eberhard Wolff We would like to thank the numerous users of Renew who provided hints and constructive criticism They helped greatly in improving the quality of the code and the documentation In particular we would like to name Alun Champion and Zacharias Tsiatsoulis 10 Chapter 2 Installation In this chapter we will give a short overview of the installati
76. art a simulation of creator the top transition can fire and creates two new net instances of othernet References to the two nets are deposited in the middle places Now three transition instances are activated namely the two transitions in the two instances of othernet and the bottom transition of creator The guard is satisfied because two different creation inscriptions are guaranteed to create different net instances You never create the same instance twice Now the order of execution is undefined It might be possible that the bottom transition of creator fires first Even in that case the two transitions instances of othernet remain activated A net does not disappear simply because it is no longer referenced On the other hand if a net instance is no longer referenced and none of its transition instances can possibly become enabled then it is subject to garbage collection Its presence has become undetectable and hence we might remove it without further ado In Java the reserved word this denotes the object whose method is currently executed In reference nets this denotes the net instance in which a transition fires 47 ll x new othernet y new othernet guard x y Figure 3 10 The net creator Figure 3 11 The net othernet ch C this ch Figure 3 12 The net synchro We are often going to treat net instances like objects of an object oriented programming language They are instances of a net just like objects are
77. ase contact the authors 125
78. at can ease the task of making an imported net readable is described in Subsection 4 4 3 Print The print menu invokes a platform dependent print dialog and lets you make hardcopies of the active drawing Using the Java standard print system though the quality of the printer output is usually very poor This is why we implemented a PostScript output feature see next section The keyboard shortcut for this function is Ctrl P Exit Tells Renew to terminate All drawings are closed as if you closed them manually which means that now Renew asks you about saving changed drawings see Subsection 4 4 1 Renew Due to the introduction of the plug in system other plug ins might still be active 2 0 when the editor is closed With respect to the simulator plug in the editor now asks you for confirmation to terminate a running simulation if there is any If you choose No then the non graphical simulation of Renew will continue To enforce that the whole plug in system is shut down when you close the editor you can configure the property de renew gui shutdownOnClose see Subsection 2 7 3 for details 4 4 2 Edit The Edit menu contains functions to insert remove and group figures and to change a figure s Z order Details can be found in the following sections Undo Redo Up to ten modifications to each drawing can be undone step by step The effect of an undo can be undone by the redo command Cut Copy Paste This function gr
79. ator is not able to establish these breakpoints Set Selection as Icon This feature allows you to assign icons to your nets These icons will be displayed during simulation whenever a place marking is displayed in token mode see subsection 4 4 5 and references an instance of a net with an icon Select exactly one figure which can be of any type then select the menu Set Selection as Icon If more than one figure was selected nothing happens but in the case of a single figure it is assigned as the net s icon When the figure is removed the net does not have a special icon so that references to this net are again displayed as text When the figure is or includes a text figure the string ID contained anywhere within the text has a special meaning During simulation ID will be replaced by the index number of the referenced net instance You can use net icons as in the following example which can be found in the samples folder icon Remember the Santa Claus example from Section B 7 Imagine you want to visualize the bag and its contents as icons Figs and 4 6 show modified versions of the nets from the Santa Claus example wakeup boots Wy deposit thing take thing esmo 2 b new iconbag m1 new muffin m2 new muffin m3 new muffin b deposit m1 b deposit m2 b deposit m3 A thing thing thing b take thing bag Figure 4 5 The net iconsanta Figure 4 6 The net iconbag 95 Add an icon to the
80. ava Series Prentice Hall 1996 115 Appendix A Contacting the Team To get in contact with us you can send an email to support renew de regarding any aspect of the Renew tool especially update notification requests bug reports feature requests and source code submissions Our postal address is Arbeitsbereich TGI Renew Department Informatik Universitat Hamburg Vogt K lln Strafe 30 D 22527 Hamburg Germany in case you do not have access to email The latest news about Renew are available from the URL http www renew de and in the same place improved versions and bug fixes appear first 116 Appendix B File Types Renew creates uses and consists of many different kinds of files that are distinguished by their file extension We will describe the most important file types here A file named contains aut an autosaved net drawing may be renamed to rnw bak a backup net drawing may be renamed to rnw bat a Windows batch file bib a BibT X bibliography class a compiled Java class draw a drawing mime type application x renew drawing dtd an XML DTD dvi a device independent output file of Tex eps Encapsulated PostScript graphics x gif a bitmap in GIF format jar a JAR compressed archive java Java source code jj a JavaCC grammar pdf a PDF document pnml one or more nets in PNML format ps PostScript graphics or a PostScript document rnw
81. awings are included in the palette without specific order There are two ways to use the net component repositories within the plugin First reposi tory folders can be opened directly using the menu command Second plugins can extend the functionality of the NC plugin by providing a repository Such a plugin can use the provided generic plugin facade PalettePlugin or a customized facade class can be provided In the latter case also other tool buttons and command line commands can be added to the sys tem Plugins using the PalettePlugin class must provide two properties for the definition of the directory and two for the automatic initialization switch de renew nc dir prop name de renew nc init prop name A minimal example for a plugin configuration file plu gin cfg is presented below More information about the concept and the tool can be found in mainClass de renew netcomponents PalettePlugin name Renew ExampleComponents provides com example nc requires de renew util de renew gui de renew nc de renew nc dir prop name com example nc dir de renew nc init prop name com example nc init com example nc dir tools com example nc init false 2 8 Troubleshooting A few possible problems and their solutions are described here If you have problems contact us If you have solutions contact us too e I cannot extract the files from the archives Maybe the files got corrupted on their way to you Maybe you are using an old versio
82. bag ml new muffin m2 new muffin m3 new muffin b deposit m1 b deposit m2 Noy b deposit m3 thing thing b take thing Figure 4 7 The Santa Claus Example with Icons During Simulation Associate Highlight It is not only possible to select the kind of feedback given for the marking of a place see Subsection 4 5 1 but also to specify arbitrary graphical elements to be highlighted whenever a place is marked or a transition is firing Each net element can have at most one highlight figure but this figure can be any Renew drawing figure like any rectangle line text etc even a group figure You can for example draw a StateChart with Renew s drawing facilities construct a net which simulates the StateChart s behavior and associate figures such that during simulation the StateChart is highlighted accordingly The first function one needs for dealing with such highlights is to associate a highlight to a net element such as a place or a transition When the menu Associate Highlight is invoked exactly two figures have to be selected of which one has to be a place or a transition The status line tells you if associating the highlight to the net element was successful otherwise displays an error message 21t is even possible to associate another net element as a highlight but this is not recommended as it can lead to confusion 96 Now during simulation the associated figure will be highlighted exactly when th
83. bag net by drawing an ellipse coloring it gray and drawing a polygon which looks like the closure of the bag Add a text with the string BAG 1D to the drawing Group together all new figures Edit Group This is necessary since the icon of a net has to be a single figure Now you can select the group and then the menu Set Selection as Icon Note that when you have to Ungroup the icon e g to move one of the included figures individually this corresponds to removing the group figure So after re grouping the icon you have to invoke the menu again or the group figure will not be set as the net s icon The next step to make an iconized version of the Santa Claus example is to create a new net add an image figure with your favorite sweet in my case this is a muffin and a text figure saying ID Then again group together the image and the text select this new group and select the menu Set Selection as Icon Save this net as muffin Now you can select the net iconsanta and start a new simulation After performing two steps the running nets may look like those in Figure Note that the reference to the net bag is now display as the bag icon with ID replaced by the net instance index 1 Without the icon the token would have been described as bag 1 Also note that the muffins all have different index numbers so that you can see to which net they refer iconsanta 11 a O X iconbag 13 O xX deposit thing take thing b new icon
84. be you should restart Renew with another net formalism 113 Bibliography 1 Y 10 Apache Logging Services Log4j 2005 WWW page at http logging apache org log4j Jonathan Billington S ren Christensen Kees van Hee Ekkart Kindler Olaf Kummer Laure Petrucci Reinier Post Christian Stehno and Michael Weber The petri net markup language Concepts technology and tools In W van der Aalst and E Best editors Applications and Theory of Petri Nets 2003 Proceedings of 24th International Conference Eindhoven The Netherlands volume 2679 of Lecture Notes in Computer Science pages 483 505 Springer Verlag 2003 Lawrence Cabac Net components Concepts tool praxis In Daniel Moldt editor Petri Nets and Software Engineering International Workshop PNSE 09 Proceedings Technical Reports Universit Paris 13 pages 17 33 99 avenue Jean Baptiste Cl ment 93 430 Villetaneuse June 2009 Universit Paris 13 Giovanni Chiola Susanna Donatelli and Guiliana Franceschinis Priorities inhibitor arcs and concurrency in nets In Application and Theory of Petri Nets 1991 Proceedings 12th International Conference Gjern Denmark pages 182 205 1991 S ren Christensen and Niels Damgaard Hansen Coloured petri nets extended with channels for synchronous communication Technical Report DAIMI PB 390 Aarhus University 1992 S ren Christensen and Niels Damgaard Hansen Coloured petri nets extended
85. ble float f int float long int char short char short byte byte Figure 3 3 The Java type hierarchy and the hierarchy of lossless conversions as classes For a detailed discussion of the Java type system and the Java system libraries we refer the reader to the literature Now we are going to look at the syntax of Java expressions We only deal with the subset of Java that is relevant to reference nets Variables are represented by identifiers Identifiers are alphanumeric strings starting with a non numeral character E g renew WRZLGRMF go4it and aLongVariableName are all valid variable names By convention variable names should start with a lower case character The declaration of a variable is denoted by prefixing the variable name with the type name e g int i Variables were already silently assumed in Fig 8 2 The Java language provides literals for integers 123 long integers 123L floats 12 3F and doubles 12 3 Furthermore there are the boolean literals true and false string literals string and character literals c Java uses 16 bit Unicode characters and strings There are no literals for the primitive types byte and short There is also one literal of reference type named null Every variable of a reference type may take null as a value null equals only itself and no other reference Trying to invoke a method of the null reference will fail with a runtime exception A sizable set of operators is
86. cally a place figure is created with its center set to the location where you released the mouse pointer and the newly created arc connects the transition and the new place cl es This feature offers you a very fast way to create reference nets Just start with a Y transition and use its blue arc handle to create a new arc and the next place Since this works for places see below too you can continue to create the next arc and transition using the arc handle of the newly created place If you want to reuse an existing place or transition just drag the arc to that figure as usual Thus you can create arbitrarily complex nets without selecting any other tool Tf you combine this with the automatic inscription generation and editing see above even colored nets will only take seconds to create The Place Tool The place tool works analogously to the transition tool only that the arc handle the small blue circle creates input arcs see previous section If the new arc is not released on top of an existing transition a new transition is created and used as the target of the arc The Virtual Place Tool The virtual place tool is used to create virtual copies of a place It improves the readability and graphical appearance of nets in which certain places are used by many transitions Other Petri net tools sometimes call such a virtual copy of a place a fusion place If the contents of a place is needed for many transitions the readabili
87. cause it might throw the simulator into an infinite loop A different search strategy could have avoided this problem but it would have incurred a significant performance cost We mentioned that message passing can be simulated by synchronous channels The canonical way would be to create a transition with a single parameter uplink and a single output arc in the receiving net which can then put the argument of its uplink into its output place Because this transition is always enabled messages can always be sent and the state of the receiver does not influence the sender in any way After the message has been put into the place it can be processed in an arbitrary way Using the special inscription x new net you can indicate that you want to create a new 50 crit manual request tok notok wait request manual Figure 3 17 The net mutex net with name net assign it to the variable x and perform a synchronization with the uplink new in the newly created net in one step Note that unlike earlier versions of Renew the channel new is only invoked when you request it explicitly An implicit invocation even for the initially created net instance is not performed For additional examples see the nets that are distributed with Renew in the directory samples Not all of them are given a detailed discussion in this manual In directory samples fireman you can find the fireman example that is based on an idea of Petri 15 A work
88. ch time you check the box or choose the Timed Java Compiler However the engine is not switched back to concurrent mode when you uncheck the box or change to another formalism 4 4 7 Windows This menu contains a list of all drawings loaded into memory The drawings are classified into Nets Net instances and Token Bags and appear in alphabetically sorted submenus A drawing can be loaded supplying its file name to Renew as a command line argument invoking the Open Drawing menu or created through the New Drawing menu A newly created drawing can be named and any drawing can be renamed by saving it using the Save Drawing as menu By selecting a drawing in the Windows menu its window is raised and becomes the active drawing window In the menu the name of the active drawing appears checked Renew Non modal tool and attribute dialogues are now included in the windows menu in 2 their own categories These windows are raised when the corresponding menu entry is selected but there is no effect with respect to the list of active drawings 4 4 8 Additional Top Level Menus The menu manager allows for the registration of a menu item by the plugins under any top level menu Additionally plugins may use a new top level name Typical candidates are Plugins Tools and Application Renew The optional plugin GuiPrompt offers its command under the Plugins menu The 2 3 NetComponents plugin and the optional pluging Diagram NetDiff and Lola re
89. clicking on an already existing figure You can then drag the intermediate point to its destination To get rid of intermediate point right click the associated handles The Inscription Tool Inscriptions are an important ingredient for most high level Petri net formalisms An inscrip tion is a piece of text that is connected to a net element place transition or arc Refer to Section B to find out what kind of inscriptions are valid in our formalism You can inscribe types and initial markings to places You can provide inscriptions for arcs in order to deter mine the type of tokens moved Transitions may carry guards actions uplinks downlinks and expressions Multiple transition inscriptions may be given in a single figure but they have to be separated by semicolons 77 z K Ed Y ES e e li When editing inscription figures you have to know that in principle they behave like connected text figures This means that all functions for connected text figures also work for inscription figures see Section The Connected Text Tool For example to check that an inscription figure is in fact connected to the net element you want it to be connected to double click on the inscription figure Then the corresponding net element should be selected Also you can drag an inscription to another net element Again in contrast to text figures inscription figures have a semantic meaning to the simulator By default inscriptio
90. could have been changed this check is a little bit pessimistic and if so asks you whether to save the drawing You have the options to answer Save now Close or Cancel Save now tries to save the drawing Drawings which already have a name are saved with that name If the drawing is untitled the normal save dialog appears see above Here you still have the option to cancel which also cancels the closing of the drawing If you select Close the drawing is closed and all changes since the last save are lost or the whole drawing if it was still untitled Last but not least you have the option to Cancel closing the drawing Export The items in the export submenu allow you to save the active drawing in several formats for use with other applications Renew The Export menu now has three submenus Export current drawing comprises 2 O export filters for the active drawing only All these filters are available through the first menu entry Export current drawing any type too where you can choose the desired export format via a drop down box in the file dialog Export all drawings single file each provides the same set of filters but there they are applied to all drawings automatically This results in one exported file per drawing these files are stored in the same location and with the same name as the respective drawing files but with a different extension Export all drawings merged file comprises export filters that are able to mer
91. cs can require that a token remains available for given time before enabling the transition For input arcs the delay must not be created by a random number generator or depend on the result of an action inscription However an input arc delay may depend on token values and indeed on the value of the delayed input token itself which means that x t t would be a legal although somewhat peculiar arc inscription Output arcs can specify that a token is only available after some time The output arc delay may be calculated in an action and it may be a random number The output arc delay cannot influence the enabling of a transition but only the timestamps of the generated tokens Double arcs can specify an output arc delay The input arc delay is always zero the token is consumed at the current time Test arcs cannot specify a time They can only access currently available tokens They put the token back with the original time stamp Clear arcs cannot specify a time They remove all tokens regardless of the time stamp Inhibitor arcs cannot specify a time They block on all tokens regardless of the time stamp Flexible arcs can remove only currently available tokens In Fig 3 29 you can see an example model of a sea port where ships arrive and are unloaded The loading of the ships is not displayed At the upper left hand corner you can see that new ships are created each ship being numbered accordingly Probabilistically it is determined wheth
92. d You can switch between servers by selecting them in the drop down box The connection stays alive until you press the Disconnect button or either Renew application local or remote terminates In the net instance list you can select a net instance and open it by double click or by pressing the Open button The title of the net instance window shows that it is the instance of another server You can use nearly all the interaction features of local net instance drawings All your modifications are executed on the server Like local simulation windows events from the remote simulation ensure that the drawings will be up to date at every time 100 j The editor is not able to display two net instances with the same name and id It will 4 bring the existing net instance window to front when you select a net instance with the same name and id from a different simulation To see the other net instance close the existing net instance window Breakpoints You can set breakpoints to stop the simulation at a predefined point of time which is espe cially helpful for debugging purposes where the simulation might have to run for extended periods of time before an interesting situation arises The breakpoint menu consists of two sections The first allows you to set and clear breakpoints and the second allows you to view all breakpoints currently set in the simulation A breakpoint will stop the search for enabled bindings when running a simulations
93. d explained in the next section 2 6 5 Sequential Mode By setting the property de renew simulatorMode to the value 1 you can request a se quential mode where transition firings are no longer concurrent There is usually little reason to do so but sometimes concurrently executed transition inscription might lead to strange results You can then select the sequential mode to check your nets Please note that net methods as described in Section 3 9 cannot be used in this mode As you might have noted the property used to configure sequential mode is the same as for multiprocessor mode So the configuration and evaluation notes given in the previous section still apply to this property If we restrict the Petri net formalism to purely sequential behavior we can add certain Petri net extensions that were not suitable for a true concurrency formalism Most notably we can use inhibitor arcs and clear arcs These extensions will be described in Subsections 3 10 2 and 3 10 3 Renew The Extended sequential mode provided by previous Renew releases has disap 2 0 peared as of version 2 0 The sequential arc types can now be added to and removed from the tool bar via the menu entry Simulation Show sequential only arcs see Section 4 4 6 If you try to simulate nets that contain sequential only features and the simulation is configured to use a concurrent engine you will encounter an error message In this case you just need to set the
94. d in Selection Tool Figure 4 1 The Renew Window There is always one active drawing window Selecting a pull down menu invokes a com mand which affects the active window its drawing or a selection of figures of that drawing unless it has a global effect only Examples of menu commands are saving or loading a docu ment or changing attributes of figures The menu commands are explained in Section 4 4 On the other hand the toolbar is used for selecting a current tool With a tool you can create or edit certain kinds of figures in a drawing All tools available in the toolbar are discussed in Section 1 3 Since each tool but the selection tool is related to a certain type of figures the corresponding figure type is also explained in that section To manipulate figures handles are used Handles are small squares or circles that appear at special points of a figure when the figure is selected Dragging and double clicking handles has varying effects depending on the kind of figure and handle Handles are also explained in the corresponding figure s section To find out how to install Renew refer to Section 2 4 You should then be able to start Renew from the command line just typing renew or using a program icon you created depending on your operation system You can also provide some drawings file names as command line parameters After typing renew just provide the path and name of one or more files including the extens
95. d instead of vector based The generated image has a fixed resolution that cannot be scaled without loss of information The PNG export is based on the FreeHep library XML There are several export formats that use XML We provide experimental PNML support since Renew 2 0 PNML stands for Petri net Markup language and has been presented at the ICATPN 2003 in 2 With Renew 2 2 the SVG format has been added With Renew 2 4 the support for the experimental XRN format provided in previous releases has been discontinued PNML http www informatik hu berlin de top pntd ptNetb This format saves the drawing as a P T net compatible with the P T net type definition in a version from sum mer 2003 Note that all drawing elements which are not needed to describe the P T net are omitted PNML RefNet This format saves the drawing as a Renew reference net Graphical figures without semantic meaning e g those figures produced by the drawing tool bar are omitted The underlying PNML type definition is experimental it may be subject to changes without notice Please note that the PNML standard allows multiple nets to be contained within one file J The Renew PNML export and import have been developed at a time where the PNML standard was still under development The code has not been revised since so that it might not comply with the current PNML standard SVG Renew This format exports the complete graphical information of a drawing into an SVG
96. d use your custom classes from the classpath but your classes cannot refer to any Renew class This problem especially affects net stubs they need to refer the NetInstance class of the simulator plug in To work around this the plug in system provides the property de renew classPath You can set the property de renew classPath to any value that follows the syntax and semantics of the Java classpath which depends on the operating system you use The property is evaluated once at startup time to configure the class loader of the plug in system changes at runtime are not recommended by Java s class loader concept All classes available through de renew classPath can be used in simulations and as plug in extensions However if a class with the same qualified name exists in a plug in and in the de renew classPath the plug in class takes precedence For your convenience the renew startup script automatically transfers the value of the CLASSPATH environment variable to the de renew classPath property at startup As long as you stick to the renew script you should be able to stick to the classical method of configuring the CLASSPATH variable to include your custom classes and stubs When you are developing an application that consists of Java code and net drawings you might want to modify and recompile your own classes and use them in your nets with out restarting Renew Therefore we provide a class reloading mechanism to simulations in Re
97. d variable A clear arc is inscribed with a variable that is typed The arc is supposed to clear an untyped place Because it cannot be safely assumed that all tokens in the place will have the correct type it might not be possible to clear the place entirely Consider declaring the variable that is inscribed to the arc 110 Cannot losslessly convert A typed place must hold only values of the given type Hence the type of an output arc expression must be a subtype of the corresponding place type The type of an input arc expression is allowed to be a subtype or a supertype but it is not allowed that the type is completely unrelated Maybe you were confused by the slight variations of the typing rules compared to Java Have a look at Subsection 3 4 2 Cannot use void expressions as arc inscriptions Void expressions do not compute a value If you use such an expression typically a method call as an arc inscription the simulator cannot determine which kind of token to move Class imported twice In a declaration node there were two import statements that made the same unqualified name well known e g import java lang Double and also import some where else Double Remove one import statement and use the fully qualified class name for that class Detected two nets with the same name The simulator must resolve textual references to nets by net names hence it is not allowed for two nets to carry the same name Maybe you have o
98. declared in each method that has a non void return type A non void method returns the value of return at the end of its body The stub description can now be compiled with the command compilestub samples call Account stub from the Unix command prompt assuming that the stub description is contained in the file samples call Account stub A similar script is also provided under Windows but for other operating systems we do not currently supply a convenient shell script but you can achieve the same effect by running java cp plugins misc 2 4 3 1 2 jar de renew call StubCompiler samples call Account stub or similar commands Now the command the classpath has to be entered on one line javac classpath loader jar libs log4j log4j 1 2 12 jar plugins util 2 4 3_1 3 jar plugins misc 2 4 3_1 2 jar plugins formalismgui 2 4 3_1 1 0 jar plugins simulator 2 4 3_1 5 1 jar samples call Account java compiles the Java source resulting in the file Account class Renew Because this command is rather long we provide the script jcompile for Unix and 2 0 Windows which includes an appropriate classpath to compile Renew related classes Just type the following command to achieve the same result jcompile samples cal1l Account java We will now use this class inside a reference net but it could be used in Java code just as well The only limitation is that the net assigned to this class has to be loaded in Renew At the moment
99. ded in the key the value or in between list prints a list with the names of all loaded plug ins The command respects some mode switches which cannot be combined 1 or long shows date and version information of plug ins if available c or comments shows compilation comments of plug ins if available j or jar shows the jar file locations of plug ins and libraries o shows an alphabetically ordered list of plug in names info prints information about one plug in The plug in s name has to be specified as com mand argument use list to see the plug in names load loads one plug in dynamically if possible The argument to this command is a URL specifying the plug in s location The plug in location can be given relative to the de renew pluginLocation directories For example load file gui jar would load the gui plug in from the renew distribution renew2 4 3 plugins gui jar unload terminates and unloads a plug in if possible The plug in s name has to be specified as command argument use list to see the plug in names If other plug ins depend on the given plug in the plug in system will complain You can add the argument v to see a list of dependent plug ins or the argument r to unload all recursively dependent plug ins are still accessible Fixing this bug requires a different plug in class loader T Although the plug in is terminated and all dependencies are cleaned its classes which will hopefu
100. dern operating systems without changes e Renew comes complete with source so its algorithms may be freely extended and im proved It is in fact possible to add special net inscriptions quickly It is even possible to implement completely new net formalisms without changing the basic structure of Renew e Renew can make use of any Java class Today there exist Java classes that cover almost all aspects of programming e Reference nets are themselves Java objects Making calls from Java code to nets is just as easy as to make calls from nets to Java code The Petri net formalism of Renew too might be very interesting for developers e Renew supports synchronous channels Channels are a powerful communication mech anism and they can be used as a reliable abstraction concept Net instances allow object oriented modeling with Petri nets While a few other net formalisms provide net instances it is their consistent integration with the other features that makes them useful Reference nets were specifically designed with garbage collection of net instances in mind which is indispensable for good object oriented programming Many arc types are available that cover almost all net formalisms Simulation time with an earliest firing time semantics is integrated There are however a few points to be aware of 1 2 There are currently only rudimentary analysis tools for Renew Although a few export interfaces have already been implemen
101. determines the action to be taken It is always a good idea to be able to close a window because otherwise an undue amount of uncloseable windows might accumulate on the desktop 3 9 3 Automatic Generation A single synchronization per method is only appropriate for the most trivial methods namely those methods that can be completed atomically Most methods will require at least two synchronizations one to pass the arguments of the call and one to collect the results A very simple scheme would require the following two channel invocations this method arg0 argl arg2 this result return When two or more concurrent method calls are allowed this scheme breaks up It becomes impossible to match the two synchronizations and a caller might receive a result that was requested by someone else Therefore we consider a more elaborate scheme where each method call is identified by some method instance value this method instance argO argi arg2 this result instance return The first channel provides the arguments to the net and receives a method instance value back We do not specify how this value is composed but it must identify the original call uniquely In the case of a void method it would not be sensible to compute a return value hence we could leave out the return parameter from the second channel invocation It still makes sense to have the second invocation though because we usually want to wait for the completion of the meth
102. ditional or different license terms and conditions for use repro duction or distribution of Your modifications or for any such Derivative Works as a whole provided Your use reproduction and distribution of the Work otherwise complies with the conditions stated in this License 7 Disclaimer of Warranty Unless required by applicable law or agreed to in writing Licensor provides the Work and each Contributor provides its Con tributions on an AS IS BASIS WITHOUT WARRANTIES OR CONDI TIONS OF ANY KIND either express or implied including without lim itation any warranties or conditions of TITLE NON INFRINGEMENT MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License 8 Limitation of Liability In no event and under no legal theory whether in tort including negligence contract or otherwise unless required by applicable law such as deliberate and grossly negligent acts or agreed to in writing shall any Contributor be liable to You for damages including any direct 123 indirect special incidental or consequential damages of any character aris ing as a result of this License or out of the use or inability to use the Work including but not limited to damages for loss of goodwill work stoppage computer failure or malfunction or any and
103. ditions The timed simulation mode was added Lists were provided in addition to tuples Breakpoints were added in order to control the graphical simulation An XML import and export facility was added A graph layout algorithm that may help in viewing nets was added More commands for arranging figures manually were provided The ability to select and deselect figures by type was added 2 9 4 Changes in Version 1 4 Modifications This was a maintenance release that provided mainly improvements in the user interface documentation updates and bug fixes Additions You can now inspect token Java objects in detail and put toolbars into their own window You can insert intermediate points into connections more easily 30 2 9 5 Changes in Version 1 5 Modifications The compatibility with Java 1 2 was improved Bugs in the simulation engine were fixed Some GUI problems were corrected The menu structure was cleaned up and simplified Additions A persistent database backing supports the deployment of the simulator in environment with high availability requirements Arcs can be B splines An alignment can be specified for every text figure Transitions and places can be refined Subnets can be coarsened Nets can be merged Drawings are now autosaved A backup copy of every file is kept Undo and redo com mands were added Search and replace commands were added The architecture guide was added which is a manual that describes the most
104. drawings open If some drawing is missing the only drawback is that its net instances will not be displayed in instance drawings As a consequence you will not be able to use the extended control features described in Section 1 5 for these nets but the menu commands Simulation step and Run simulation will still work and trace events will still be logged This holds even if no drawing used by the saved simulation state is loaded at all The mapping from a compiled net contained in the saved state to an open net drawing is done by the net s name This mapping occurs every time when you try to open an instance drawing for any instance of the net If you added to or removed from the net drawing any transitions or places since the simulation state was saved some messages informing you about the problem and its consequences are printed to the application log An instance drawing will still be opened but it will not necessarily display the same structure that the compiled net uses Further points to be aware of e If you load a simulation state any running simulation will be terminated and all related windows are closed e Tf the class reinit mode is selected see Subsection 2 6 6 custom classes will be reloaded while restoring the simulation state 102 e All custom classes used in the saved simulation state must be available when restoring the state Show simulation trace Renew This menu command opens a window that shows the trace of
105. e Plug ins Temporarily To hide installed plug ins from the plug in finder at startup you can specify the property de renew plugin noLoad either via D command line option or the renew properties file see Section 2 6 1 for details The value of the property is a comma separated list of plug in names For example the line java Dde renew plugin noLoad Renew JHotDraw jar renew2 4 3 loader jar gui will start the plug in system but terminate with the complaint that the gui command is unknown Because the JHotDraw plug in has not been loaded all dependent plug ins can also not be loaded This affects the Renew Gui plug in which would otherwise have provided the gui command Of course it would make more sense to use some non graphical command like startsimulation instead 2 7 3 System Termination The plug in system tries to detect the situation where no plug in is active and therefore the system can be shut down Plug ins are active if they have some long term work to do This always holds for the windows of the graphical editor A running simulation also counts as active The prompt plug in has a special keep alive flag which marks it as active see Section 2 7 5 Besides automatic termination the plug in system can be terminated by request The exit command see Section 2 7 4 has just that purpose The editor may also terminate the plug in system when it s main window is closed The editor does this not by default you
106. e a database so that the number of tuples in a place can be considerable Often one component of an input arc tuple can be determined without accessing the place In this case Renew accesses only those tokens that match the known component Because few tokens need to be checked the simulation can proceed quickly If two components of the input arc tuple are known the simulation engine will use that component as a key that results in fewer matches In functional programming nested pairs are used as a representation of lists This could be simulated by nested tuples but it would result in nets that are hard to read Hence we added explicit list support to the language Lists are delimited by curly braces e g 1 2 3 4 would be a four element list Lists like tuples support pattern matching Using 1 2 3 4 u v w x as a transition inscription we would get u 1 v 2 and so on 46 dos 1 0 0 11 li i li I OT AO tl hd 1iJ hd tH li Figure 3 9 The net reverse In order to handle lists of unknown length a tail expression may be added to the list The tail expression is separated from the ordinary list elements by a colon The tail expression matches an arbitrary list of elements By requiring 1 2 3 4 u v w we get u 1 v 2 and w 3 4 The tail consists of all elements that are not explicitly represented The tail may be empty as in 1 2 3 4 u v w x y where y Note that the empty tuple and the empty list
107. e first property defines the base directory for the navigator plugin It needs to be an absolute path like path to renew2 4 3 or c path to Renew2 4 3 The second property is a semicolor separated list of paths relative to the base directory All folders and files defined in this list will be added to the tree area on startup Example MyNets Core samples home renewuser exampleNets Open URL Renew Renew can now load drawings from a remote location specified by a URL This 2 0 command opens a dialog where you can type the URL and press OK Note that Renew is not able to save drawings to URLs it still requires a local file name TA semicolon has to be used even on Unix based systems where paths are usually separated with the colon 79 Open Drawing This function displays a file selector dialog that lets you select a drawing that was saved previously The file selector dialog looks a little bit different depending on the platform but always allows you to browse the file system and select an existing file By pressing the OK button the selection is confirmed and Renew tries to load this file as a drawing If that does not succeed an error message is displayed in the application log and in the status line of the Renew window Otherwise the drawing is added to the list of drawings in memory see Section 1 4 7 and opened in a new drawing window The keyboard shortcut for this function is Ctr1 0 Renew The open dialog n
108. e formats import any type The first entry of the Menu combines all import filters into one dialog where you can choose the desired format from a drop down box For window managers where this drop down box is not available the separate menu entries are still available XML Renew Analogous to the export features described in subsection 4 4 1 Renew now provides 2 0 several XML import filters 83 XML Imports a file in the obsolete XML format of Renew 1 6 Whenever possible the graphical and semantic information is restored from the file Note again that you will not be able to import an XML file of a different Renew version with this command This feature has been cannot be used anymore Its support has been discontinued PNML Tries to import a file in PNML format The filter automatically guesses the net type used in the PNML file It tries to extract as much graphical and semantic information as possible from the file Shadow Net System Lets you import a previously exported or automatically generated shadow net system see above Since a shadow net system does not contain any graphical information the places tran sitions arcs and inscriptions are located in a rather unreadable manner Thus this function only makes sense for shadow net systems automatically generated by other tools After im porting it is of course also possible to edit all nodes and inscriptions in a normal fashion An automatic graph layout function th
109. e g MySQL does not support transactions when using the default MyISAM engine use InnoDB instead Having created the tables you should configure a set of properties to enable the database backing feature see Table 2 2 These properties are evaluated each time a simulation is set up The class names specified for the driver and dialect properties should be accessible Property name Type Comment de renew simdb driver class JDBC driver class mandatory de renew simdb url URL JDBC connection URL mandatory de renew simdb dialect class Subclass of de renew database entitylayer SQLDialect optional de renew simdb user string User account for database login optional de renew simdb password string Password for database login ignored when de renew simdb user is not set Table 2 2 Properties to configure database backing via the de renew classPath see Section 2 6 6 The dialect class is an internal class that adapts Renew to the SQL dialect of your database The default is the generic SQLDialect but for some databases we already provide experimental implementations like OracleDialect MySqlDialect or MSqlDialect When using the database backing your nets must conform to certain restrictions Un fortunately these restrictions cannot be checked by Renew automatically so that you must take special care when preparing your net All tokens used in your net must be serializable i e custom classes must implement java io Serializab
110. e net element is highlighted If the associated figure is invisible it will be made visible whenever it is highlighted If the figure is already visible its color will change as a result of the highlighting Select Highlight s To find the associated highlight figure see above to a net element select the net element and then this menu If the net element does not have any highlight figure a corresponding message appears in the status line You can also select multiple net elements and all associated highlight figures of any one net element of the group will be selected Unassociate Highlight Sometimes you also want to get rid of a highlight association see above Then select one single net element place or transition with an associated highlight figure and then invoke this menu When you associate a net element to a highlight figure any old association is automatically canceled Syntax Check This menu entry checks the net for syntax errors without starting a simulation run Of course most syntax errors are immediately reported after the editing of an inscription but not all errors are found this way E g multiple uplink inscriptions cannot be detected immediately You can also invoke a syntax check when you have corrected one error in order to make sure that no other error remains It is always a good idea to keep the nets syntactically correct at all times Layout Check This menu entry checks in all loaded drawings whe
111. e nets types play two roles A type may be an inscription of a place This means that the place can hold only values of that type The net simulator can statically detect many situations where type errors might occur i e when transitions try to deposit tokens of the wrong type into a place Furthermore variables may be typed This means that the variable can only be bound to values of that type In Java every variable needs to be declared There are of course many good reasons to demand this but there are times when it is valuable to write programs without having to worry about a type declaration One of these cases are throw away prototypes which are supposed to be developed very quickly Petri nets are generally usable for prototyping so we wanted to be able to write nets without having to declare variables But for stable code that will be used in a production application types are a must There fore reference nets provide the option to create a declaration node In the declaration node an arbitrary number of Java import statements and Java variable declarations are allowed If a declaration node is present then all variables must be declared This means that you have the choice between complete liberty no variables can be declared and complete security all variables must be declared Note that an undeclared variable does not have a type Therefore the type of an ex pression can only be determined at runtime if it contains undeclared v
112. e one uplink has to be a downlink Unknown net In a creation expression an unknown net name occurred Maybe the name is misspelled Maybe you have not opened the net in question Variable declared twice In a declaration node there were two declarations of the same variable Remove one variable declaration Variable is named identically to an imported class In a declaration node there was a variable declaration and an import statement that refer enced the same symbol e g import some where Name and String Name This error is rare because by convention class names should start with an upper case letter and variable names should start with a lower case letter You should probably rename the variable Variable of array type expected If a clear arc is inscribed with a typed variable that variable should have an array type so that the set of all tokens can be bound to the variable in the form of an array You should check whether the correct variable is used and whether the variable is correctly typed 4 7 3 Late Error Messages Here we discuss the error message that is not reported during the immediate check but only during the complete check before the simulation 112 Unsupported arc type An arc of the net was of an illegal type i e the current net formalism does not support it This can only happen when you execute a net with a net formalism that is incompatible with the net formalism that was used to draw the net May
113. e permitted to use works that you create with Renew i e Java stubs net drawings PostScript output simulation states and other exported data without restrictions D 4 Disclaimer We distribute Renew in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose We are not liable for any direct indirect incidental or consequential damage including but not limited to loss of data loss of profits or system failure which arises out of use or inability to use Renew or works created with Renew This clause does not apply to gross negligence or premeditation Some parts of Renew may use patented techniques that may not be freely usable in some countries In that case it is the responsibility of the user of Renew to obtain a license on the aforementioned techniques before using Renew Some parts of Renew may include additional disclaimers in their license terms In such cases both disclaimers hold simultaneously If one clause of any disclaimer is found invalid 124 under applicable law this does not affect the validity of the remaining clauses or of other disclaimers The applicable court is Hamburg Germany D 5 Open Source This license is intended to be Open Source compliant If you find any clause within this license that is incompatible with the guidelines set forth in the Open Source definition see http www opensource org osd htm1 ple
114. e syntax check whenever an inscription has been changed Additionally a syntax check is done before the first simulation step of a model The simulation will not start if there is any error in any net If an error is detected an error window is opened which displays the error message At the bottom of the window is a button labeled select Pressing this button selects the offending net element or net elements and raises the corresponding drawing If the error originates from a text figure that figure is edited with the corresponding text edit tool The cursor is automatically positioned close to the point where Renew detected the error For more information on editing see Section 4 3 2 The Text Tool Renew displays exactly one error at a time If a second error is found the old error message will be discarded and the new error message will be displayed in the error window Some errors are not reported at the place where they originate E g if you are using a declaration figure an undefined variable is detected where it is used but the missing definition has to be added to declaration node Similar effects might happen due to missing import statements This is unavoidable because Renew cannot tell an undeclared variable from a misspelled variable 107 4 7 1 Parser Error Messages If the expression parser detects a syntax error it will report something like Encountered do at line 1 column 3 Was expecting one of new lt IDE
115. el More details can be found in Section 2 7 6 The background of expanded tokens in instance simulation drawings can be changed to be transparent by setting the property de renew gui noTokenBackground Several keyboard shortcuts have been changed and more have been added especially for selecting the main drawing tools A comprehensive list of existing shortcuts can be found in Appendix 34 Relevant for Developers only Generics are now used throughout the code The RMI functionality which was formerly included in the Simulator plugin was extracted into a new Remote plugin The lock functionality was moved from the Simulator to the Util plugin There are several changes to the Ant build environment The Ant target clean in the meta build file now iterates over all subdirectories instead of having a fixed list of plugins Source files of nets rnw can optionally be included in the generated plugin archives jars with the Ant target rnw To activate this function you need to set the property option include rnws in your Ant properties build xml of the plugin in question or ant local properties The property option sns compile switches the syntax check for shadow net files sns on and off The Ant target javac accepts an encoding parameter which is set via the property option compile encoding and defaults to utf 8 The Ant task createpng allows to export net drawings to png files 2 9 15 Changes in Version 2 4 Modifications The supp
116. eload custom classes during development The Eager simulation mode setting equivalents the de renew eagerSimulation prop erty explained in section 2 6 3 It allows the simulator to run ahead without having to wait for the graphical animation display Renew The Simulation priority sets the priority of each thread the simulation spawns 2 2 Higher values allow for faster simulations but might result in reduced GUI respon siveness The default value of 5 is considered a good tradeoff between speed and gui response time Remote Access The options provided by this tab find their equivalents in the remote properties which are explained in section 2 6 9 When you check Enable remote access the simulation will be published over Java RMI to allow remote inspection and simulation control this feature needs a running RMI registry to work To distinguish multiple simulations on the same registry you can assign a Public name to the simulation Plug In developers might be interested in the possibility to replace the remote Server class by a custom implementation A custom RMI Socket factory can only be supplied at startup therefore this property cannot be changed here To observe the simulation from a remote editor use the the Remote server command explained in section 4 4 6 Net path This tab allows the manipulation of the de renew netPath property used by the net loader see section 2 6 7 On the left you have a list of path entries one director
117. ems in a running simulation became more detailed The command line tool ShadowTranslator and the corresponding Ant task now optionally include the specified formalism and a syntax check Fixed transition modes of bool net compiler Fixed manual transitions in saved simulation states The color and font attribute dialogues were improved Whitespace only inscriptions are now deleted automatically like empty ones The GuiPrompt plug in now provides a text area for command feedback The binding selection frame is now scrollable Tool windows and dialogues are now listed in the Windows menu Breakpoints pre set via the Net menu are now visually tagged Fixed some drawing edit bugs in the GUI Fixed some rare deadlocks in the token game display Improved scrolling effect of mouse wheel in drawings Fixed handling of polygons Some important changes to configuration properties are documented in the upgrade notes see Section 2 3 Developers might also have a look there because of some code changes The set of Ant build files that come with the Renew source has undergone some changes The build process now stores information about the compilation environment with the plug ins Distribution file names can now optionally include version information The list and info commands optionally display this information 32 Additions All Renew components except the console prompt now use the Apache Log4J logging frame work instead of Java console output In
118. ent options to the context menu in the simulation trace window The 33 net stub compiler now additionally supports stub objects that wrap themselves around an existing net instance during instantiation before a stub object always created its own net instance We provide a MacOS X application bundle as well as configuration files for the FreeDesk top e g Gnome environment that allow desktop integration with separate icons and mime types for Renew document files However there is still no such support for the Windows family of operating systems Relevant for developers only GUI and simulation have been separated so that they use different threads now All calls to the simulation are decoupled and executed in specialized simulation threads All calls to the GUI are delegated to or synchronized with the AWT event thread Simulation threads can now be configured with a separate priority Loading of user supplied classes in the context of simulations has been improved A new parameter netpath has been added to the Ant task to create shadow net systems The Ant build environment has been enhanced to support separate source code trees for JUnit tests and Cobertura coverage reports However there still are nearly no test cases implemented Several tools that form the Renew build environment are now required in newer releases Please refer to the readme file in the source package 2 9 14 Changes in Version 2 3 Modifications Java 1
119. er jar gui mind the drive letter and the use of backslash instead of slash The gui part at the end of the line is a command that tells the loader to start the graphical user interface of Renew Note that for Unix and Windows 2000 XP Vista 7 8 we provide ready made startup scripts already They will be generated when Renew is installed In that case you do not have to provide a loader command manually and some classpath related issues see Section 2 6 6 are handled more conveniently for most use cases See Section 2 5 for details 2 4 2 Source Installation Usually there is no need to do a source installation If you feel confused by this section simply skip it Extracting the source distribution will put files into the directories renew2 4 3 src and renew2 4 3 doc Renew The sources are now accompanied by build xml files for the Apache Ant tool 2 O You should install Ant to build Renew from sources it is available at http ant apache org Further you will need the unit testing package JUnit the parser generator JavaCC and the code beautifier Jalopy to compile the sources See the file renew2 4 3 src README that lists the software packages and versions you need and gives some hints on how to compile and run the application Renew JUnit and Jalopy are no longer mandatory to build Renew from sources 2 4 After you have successfully built Renew you can test your compilation result Just follow the instruct
120. er the ship needs unloading If yes the ship is unloaded and the customs declarations are checked concurrently The ship is unloaded by one of three cranes where the unloading takes six hours on average with a negative exponential distribution Two customs officers handle declarations in three hours but they need another two hours for filing afterward If a declaration is not handled for at least five hours the chief customs officer 63 Miller 10 Renew Street Jones 117 Java Park Smith 42 Petri Avenue go y Guthotadar En name addr O Smith Smith this getAddress author getAddress name addr authorAddr this getAddress editor editorAddr editorAddr Figure 3 30 The net reserve helps processing the forms He does not look very carefully and needs only one hour in total With the good and the signed customs forms a truck may leave the port After another hour of cleaning up the ship may be reloaded Note how we use a reserve arc to model a resource that is unavailable during some time An input arc delay was used to prioritize the ordinary customs officers over the chief officer and to force the chief officer into action at the right time You might want to try to add different unloading times to the three cranes Try to model the loading of the ship Consider partial unloading of ships Try to convert the net to an object oriented design where the port the cranes the ships and the officers are all
121. ers The Line Tool The line tool produces simple lines that are not connected see also the next section The Connection Tool Creating a line is similar to creating a rectangle Press the primary mouse button where the starting point is supposed to be and drag the mouse to specify the end point while holding down the mouse button The line figure has two sizing handles small white boxes in order to let you change the starting and end point afterward It also has an intermediate point as described in Section The Connection Tool A line figure has no fill color but it respects the pen color see Section 4 4 4 The Connection Tool This tool lets you create connections arcs between other figures A connection is like a line except that it connects two existing figures and is automatically adapted every time one of the connected figures changes Consequently the location of pressing down the mouse button does not specify a starting point but a starting figure Again the mouse button has to be held down while dragging the end point of the connection If an appropriate figure is found under the mouse button the end point snaps into this figure s center This figure is confirmed as the end point figure as soon as you release the mouse button The connecting line always is cut off at the outline of the start and end figure so that it just touches their borders A connection can be re connected using its green square connection
122. erves requests for everyone A transition that is called through an uplink need not know the identity of the initiator just like an activated method of an object does not necessarily know of its caller Therefore the expression that designates the other net instance is missing for uplinks An example uplink inscription would look like ch x y z which means that the channel name is ch and that the three channel parameters must match the binding of the variables x y and z The uplinks and downlinks of a transition may be given as individual transition inscrip tions or in a single semicolon separated list in one inscription The list might even include action inscriptions and creation inscriptions simultaneously with the channel invocations Let us first look at the special case where two net instances within the same net syn chronize This is done by providing the keyword this as the target of the downlink In Fig 3 12 you can see an example net with local channels which is provided in the directory samples channel like all other nets of this section The input place of the left transition is marked and the transition s downlink specification can be met by synchronizing with the right transition Both transitions fire synchronously such that one token is removed from the left place and one token is added to the right place in a single step Now no more transitions are enabled The left transition lacks a token on its input place the right transi
123. es informing about tokens flowing through this arc are omitted Renew With the integration of the Log4j framework see Section 2 6 10 the need for the 2 1 trace attribute has been reduced The configuration of Log4j is much more flexible it allows for multiple log event targets with individual filter criteria while the trace flag globally controls the generation of log events for a net element A valid reason to still use the trace attribute may be the simulation speed when you want to discard the trace anyway but Log4j is rather efficient in such a situation too Please note that Renew provides a graphical Log4j configuration dialog for simulation traces see Subsection 4 4 6 Marking This menu controls the default as well as the current choice how the contents of each place is to be displayed during simulation There are four ways to display the marking of a place during simulation Either the marked places are simply highlighted in a different color highlight only or the number of tokens is shown Cardinality or the verbose multiset of tokens Tokens is shown or each token and its attributes is shown in detail expanded Tokens This is also the default mode for current marking windows However these modes can be switched at drawing time and at simulation time using the Marking menu 93 Renew The expanded token mode relies on the undocumented feature structure fs formal 2 0 ism to display object attributes Since the f
124. es that are associated with a net In this way it is possible to keep the nets free of unneeded detail Of course the helper classes need some changes occasionally and have to be recompiled If the helper class was already used in the simulator at the time of recompilation e g in a previous simulation run then the Java virtual machine will not load it again Instead it will continue to use the old version of the class To reload new classes you either have to close and restart Renew entirely or use the class reinit mode as described in subsection 2 6 6 65 3 12 6 Net Stubs A net stub see 3 9 is created with the name of its associated net At runtime the net stub tries to find a net with this name but it will only succeed if the net is already compiled or if the net is accessible through the net loader see section 2 6 7 If not the constructor will throw an unqualified RuntimeException When using a stub declared with for net netname it is important that the stub object is created instead of the net instance itself This means that the net should not be instantiated by the usual new inscription The constructor of the stub class must be used because such a stub is not able to wrap an existing net instance The alternative declaration for netinstance allows wrapping of net instances but creates a second object Calls to stub methods or the stub constructor should be encapsulated in action in scriptions because these methods cannot ter
125. es uses the logs home property see above so that you get two log files renew 1og and simulation log in that directory The former comprises application messages while the latter stores simulation traces In the default configuration application log messages are also printed to the Java console but the simulation trace is not The logging plug in provides a graphical user interface that displays the simulation trace and allows flexible configuration of logged events see Section 1 4 6 2 7 Plug ins Renew As of Renew 2 0 the application is controlled by a plug in system The system 2 1 started through the class de renew plugin Loader which replaces the different startup classes of previous releases e g de renew gui CPNApplication The loader sets up some class libraries and then loads the main plug in manager The plug in manager finds loads initializes and terminates plug ins but it knows noth ing about Petri nets The Renew functionality is provided by a set of plug ins More plug ins can be installed to extend Renew In this section there will be a lot of examples with file names and directories These are all given in Unix syntax Users of other operating systems please transform these examples to your appropriate syntax 2 7 1 Install Plug ins There are two ways to install a plug in If it comes in one single jar file which includes a file named plugin cfg you can just copy the file in the renew2 4 3 plugins directory
126. es will not produce the nicest net graph in many cases but they can ease the early stages of the layout considerably They might also be used to maintain a layout during early prototyping phases when the structure of a net changes constantly In order to improve the layout of the graph a special window pops up that allows you to control some parameters or the physical model using sliders The first slider controls the length of the springs Some diagrams tend to clump together too much which might can be a reason to raise this value On the other hand the spring might be too rigid not allowing some springs to stretch to their optimal length In that case you can control the rigidity of the spring with the second slider The repelling force acts only up to a certain distance By default the force is quite far reaching and establishes a nice global spreading But you may want to reduce this force s maximum distance in order exclude only overlapping nodes In that case it may also be good idea to increase the repulsion strength 88 The torque strength controls whether the arcs are supposed to be very strictly horizontal or vertical Initially this force might actually inhibit the progress toward to optimal layout but in the end it helps to get a nice net Try to vary this slider s position during the layout for optimal results Lastly the friction slider may be lowered so that the motion is faster overall Use this slider with care beca
127. esults in a rather clumsy net structure Now we can see the two kinds of flexible arcs in action on the right hand side One transition puts five tokens onto a place and another transition removes all five tokens atomically The simplification of the net diagram is quite obvious Currently flexible reserve arcs are not supported They will be added as soon as somebody points out a useful application for them Flexible test arcs can be added too but even their graphical representation is not obvious right now In general we reserve the right to make some modification to the handling of flexible arcs if some other syntactic or semantic variant proves superior arc expression does not evaluate to an array or collection object as explained above In such cases flexible output arcs fall back to shove the unmodified token into the output place while flexible input arcs do not activate the transition This is obviously not a symmetric behavior we The current implementation of flexible arcs shows inconsistent behavior when the In the book I7 Reisig applies flexible arcs to model distributed algorithms He uses algebraic Petri nets which are in general not accessible for Renew However in the given context only very specific algebras are used namely those that represent communication topologies in a distributed system Therefore it is possible to implement an interface Topology that captures the signature of the most common algebraic operations
128. ets The inscription language of Java reference nets is case sensitive However if you create untyped nets without any variable declaration in the declaration node there might be an exception depending on the operating system you are using In untyped nets Renew has to guess whether a particular identifier denotes a class or a variable It does so by checking for classes with a matching name in the configured class loader which in turn looks up all file locations in the class path On operating systems with a case insensitive file system e g Windows the class loader might find a class that matches the queried name except for the case Renew then reports a class with a linkage problem referring to a NoClassDefFoundError or similar The problem occurs especially when you use class and variable names that differ only in case Although this is acceptable in nets with explicit variable declarations you should avoid this technique in untyped nets 66 Chapter 4 Using Renew Renew offers a graphical user friendly interface for drawing reference nets and auxiliary graphical elements The net editor contained within Renew is based upon a Java library called JHotDraw 8 The basic drawing capabilities are mainly taken over from JHotDraw while the PostScript output the multi windowing GUI the net editor figures and tools and the image figure tool have been implemented by the Renew team Still this manual covers a complete description
129. eveloper because occasionally an array is more difficult to generate In those cases where it is not feasible to use arrays Renew support the use of expressions of the types de renew unify List see section 3 5 for details and java util Collection For output arcs it is allowed to use java util Enumeration and java util Iterator objects beside those types listed above But due to the missing type safety arbitrary values 58 inscription arc transition i Mein a a 4 Em m_ 0 place guard i gt 0 action a i x a i 1 a i a 1 new String 5 4 Figure 3 24 The net flexible can be contained in these container objects Hence output places for flexible arcs using the container objects must be untyped It should be noted that flexible arcs do not help the simulator to find information about possible bindings In some other tools all possible combinations of tokens are tried for of flexible input arcs possibly binding variables inscribed to the arc This was seriously considered but the performance cost turned out to be prohibitive At the same time the need for such an algorithm was not obvious The net from Fig which can be found in the directory samples arcs illustrates the use of flexible arcs On the left hand side you can see a classical way to remove five tokens from a place by looping with an explicit counter One after another the tokens are collected and assigned to an array which r
130. f this button as a revert button that restores the most recently applied configuration Update from simulation refreshes the dialog to display the configuration of the running simulation if there is any These settings may differ from the current simulator plug in configuration so you might want to press Apply or OK afterward to bring the plug in configuration back in sync with the settings of the running simulation OK applies the current configuration like Apply would do and closes the dialog Close closes the dialog and discards any setting changes unless they have been applied before The tabs provide the following options Engine The two options Sequential mode and Multiplicity configure the concurrency of the simulation engine The sequential mode is of interest when you work with a timed formalism see section B II or special arc types see section 4 4 6 Multiple simulators may enhance the performance on multiprocessor systems A sequential mode with multiplicity greater than one is not sequential because it uses multiple concurrent sequential simulators The settings are equivalent to the de renew simulatorMode property mentioned in sec tions and Just think of the Sequential Mode check box as the sign of the simulatorMode value if you enter a minus sign in the Multiplicity field it is ignored The Class reinit mode setting equivalents the de renew classReinit property ex plained in section 2 6 6 It allows you to r
131. flow system of a law enforcement agency is the basis for the nets in samples prosecute They are based on the article 18 where this example is attributed to W M P van der Aalst 3 8 Manual Transitions The manual inscription if attached to a transition stops the simulator from firing the tran sition automatically You have to fire such transitions with a right mouse button click This is useful for simulating external events or for adding control switches In the directory sample simple you can find the net mutex which is also displayed in Fig It shows a mutual exclusion algorithm that uses only a single channel per direction for both token transfers and token requests The critical sections that are guarded by the mutex algorithm are painted red The left process is shown in yellow whereas the right process is shown in dark green Initially the left process holds the token to enter the critical section in its place tok The right process does not own the token After one of the blue manual transitions is fired the associated process tries to gain the token and enter the critical section To see this run the simulation continuously The manual transitions do not fire automatically but after one of them is fired by using the middle or right mouse button the rest of the net processes the request immediately 51 crit zamount amount 0 old deposit amount MO E mone deposit amount y old amount P withdraw withdraw amou
132. fly back and feed his reindeer There are actually a few other ways to implement method calls on the level of nets E g one might create a new net instance for each method call and pass the arguments of the call 97 action thing bag nextElement boot thing Ibag true bag false bag bag more bag bag i action bag action more new samples call EnumBag bag hasMoreElements Figure 3 23 The net enumsanta to it This way the net instance itself could be used to identify the call and the transitions that handle the call could be moved to another net thereby leading to a much cleaner design The method net instance could either deposit its result in the common result pool as shown in the previous example or the result transition could take the result directly from the method net instance by yet another synchronous channel 3 10 Additional Arc Types Besides those arcs that are commonly found in Petri net simulators Renew implements a couple of additional arc types that are somewhat rarer but still quite useful This is done to achieve the maximum usability for different users by providing adequate modeling tools It is sometimes argued that these arc types violate the spirit of true Petri nets In some sense they do Test arcs too carry the stigma of bad concurrency semantics But let s not ban these extensions so rapidly They have their uses and they can simplify certain models considerably If you are unsu
133. free license to use modify and redistribute this software in source and binary code form provided that i this copyright notice and license appear on all copies of the software and ii Licensee does not utilize the software in a manner which is disparaging to Sun This software is not designed or intended for use in on line control of aircraft air traffic aircraft navigation or aircraft communications or in the design construc tion operation or maintenance of any nuclear facility Licensee represents and warrants that it will not use or redistribute the Software for such purposes We would like to explicitly point out that Sun is not responsible for any problems that might result from the use of the graph layout algorithm See the source files for Sun s original disclaimer 122 D 1 6 The Log4j Package Renew comes with an unmodified binary distribution of the Log4j package from the Apache Logging Services project The package is licensed under the Apache License Version 2 0 The full license is included in the distribution a copy of the License may also be obtained from http www apache org licenses LICENSE 2 0 The relevant license information states 2 Grant of Copyright License Subject to the terms and conditions of this License each Contributor hereby grants to You a perpetual worldwide non exclusive no charge royalty free irrevocable copyright license to reproduce prepare Derivative Works of publicly d
134. g violates the design rule that bags should implement the java util Enumeration interface Now a simple command makestub samples call EnumBag enumbag java util Enumeration creates the file samples ca11 EnumBag stub On some non Unix machine you might have to use the command java cp plugins misc 2 4 3_1 2 jar plugins simulator 2 4 3_1 5 1 jar 1 plugins util 2 4 3_1 3 jar de renew call StubGenerator samples call EnumBag enumbag java util Enumeration which has the same effect but is a little longer Now the stub file can be compiled as described in Section 3 9 1 i e by calling compilestub samples call EnumBag stub jcompile samples call EnumBag java or equivalent commands Fig 3 22 shows the net associated to the new stub After nextElement is invoked a new object is created that serves as an identifier for this call It is also checked that there are still items in the bag before proceeding An item is taken out of the bag and passed back The result transition can be shared for both methods because it simply takes the results from a place and forwards them through the uplink Note that the bags are now filled by the manufacturer instead of Santa due to a request of his worker s union Hence Santa s procedure has to change too In Fig 3 23 you can see Santa distributing the Christmas presents Again all presents are dropped into the boots over time but now Santa knows when his bag becomes empty so that he can
135. ge all drawings into one file Since this feature must be supported by the format of the exported file the set of export filters in this submenu is restricted The export formats included in the basic Renew distribution are listed as follows PDF This function produces a PDF document that contains the current drawing A file with the default extension of pdf is generated The Renew FreeHep Export plugin provides the de renew io export pageSize and de renew io export pageOrientation configuration properties which influence the page layout of generated PostScript and PDF files Possible values for page size are A3 AS Ad A6 International Letter Legal Executive Ledger and BoundingBox Possible values for orientation are portrait and landscape The properties default to BoundingBozx for page size in portrait for orientation However orientation does not apply if page size is set to BoundingBoz PostScript This function produces PostScript code that renders the current drawing A file with the default extension of ps is used to store the PostScript code EPS Ifyou want to include net drawings into written material you should use an Encap sulated Postscript EPS file instead of an ordinary Postscript file The EPS file can be used to insert graphics into other documents e g in LaTeX OpenOffice Microsoft Office and others EPS files are not of a fixed page size Instead their bounding box matches exactly the dimensions of the
136. generated In this case we use the class samples call Account samples call seems to be the right package because the package name should reflect the directory it is in The full stub definition file can now be presented package samples call class Account for net account void deposit int amount this deposit amount void withdraw int amount 4 this withdraw amount int currentAmount this amount return 52 action acc new action action amount samples call Account acc deposit 500 acc currentAmount Tl create deposit query init created deposited amount amount acc acc acc account Figure 3 19 The net customer The declaring package is given in a special statement which is optional The keywords for net separate the class name and the net name The body of a class description consists of a sequence of method descriptions and construc tor inscriptions In our example we do not have constructors such that a default constructor will be automatically inserted The body of each method consists of a sequence of channel invocations and variable declarations separated by semicolons As in reference nets variables need not be declared If variables are declared they must be declared before they are used In our example there are no variables except for the input pa rameters and the special variable return which is used in the last method currentAmount This variable is automatically
137. generated in the exported net Shadow Net System A shadow net system can comprise one or more nets which can be used by the non graphical simulator see section 4 6 the net loader or other tools Only the semantic information is contained in the shadows but not the visual appearance The current formalism see section 4 4 6 and the configuration of simulation traces for individual net elements see section 4 4 5 will be stored within the shadow net system As merged file A shadow net system that contains all nets needed for a simulation can be generated by the N to 1 entry in the Export all drawings merged file menu Before exporting a collection of nets to the shadow simulator it is recommended to do a syntax check on the net Although any syntax errors in the nets will be detected before the start of a non graphical simulation fixing these errors requires the editor The current formalism see section 4 4 6 and the configuration of simulation traces for individual net elements see section 4 4 5 will be stored within the shadow net system As single file each These files are well suited for the net loading mechanism described in subsection 2 6 7 The command does not require any additional interaction all file names are derived from the corresponding drawing files If a drawing has not been assigned a file name it is skipped during the export Import The items in the import menu allow you to load drawings from different fil
138. ginally written by Doug Lea and released into the public domain You can use it as you want Please note that Doug Lea now suggests to use the container libraries that come with Java 1 2 instead of his own libraries We are currently working on the migration so far all plug ins except the FS plug in have been adopted to the Java container classes D 1 2 The JHotDraw Package The JHotDraw graphical editor written by Erich Gamma is copyrighted The relevant license information states JHotDraw is copyright 1996 1997 by IFA Informatik and Erich Gamma It is hereby granted that this software can be used copied modified and dis tributed without fee provided that this copyright notice appears in all copies D 1 3 Code Generated from JavaCC Some of the code of Renew was generated by the parser generator JavaCC The relevant license information states 121 3 DEVELOPED PRODUCTS You may use the Software to generate software program s Developed Pro grams Sun claims no rights in or to the Developed Programs 4 YOUR INDEMNIFICATION OF SAMPLE GRAMMARS DERIVATIVES AND DEVELOPED PRODUCTS You agree to indemnify hold harmless and defend Sun from and against any claims or suits including attorneys fees which arise or result from any use or distribution of Sample Grammar Derivatives and or Developed Programs Hence we would like to explicitly point out that Sun is not responsible for any problems that might result from the use
139. handles and is only effective if the choice is not larger than the number of handles plus one Round corners This attribute influences the behavior of round rectangles when they are scaled When set to fixed radius the size of the curvature will remain unchanged regardless of the scaling of the figure Nevertheless an explicit modification of the radius is still possible by using the special yellow handle This is the default which was exclusively used in previous releases of Renew The setting scale with size will adapt the curvature size when the rectangle is scaled so that the proportion of the rectangle used for the curvature remains the same Font Only applicable to text based figures this attribute sets the font for the complete text of this text figure Not all fonts are available on all platforms It is not possible to use several fonts inside one text figure but still this is a graph editor not a word processor or DTP application Renew The other entry at the end of the list of colors opens a font selection dialog that 2 1 works like the color dialog described under Fill color The font selection dialog includes other font attributes like the size or italic and bold style options Caution If you use non standard fonts the text will show up differently on systems where the fonts are not installed 91 Font Size Only for text based figures select one of the predefined font sizes given in point with this menu The o
140. hanism The configuration options of Log4j would occupy to much space in this manual please have a look at the documentation section of the Log4j homepage I With the Renew distribution comes a commented default configuration file renew2 4 3 config log4j properties 23 Renew looks for Log4j configuration files at similar locations like its own renew properties files see Section 2 6 1 The configuration files can be in XML syntax or in the Java prop erties format and must carry appropriate file extensions The first file found in the following list of candidates is used 1 A file named in the system property log4j configuration at the java command line with the D option 2 10g4j xml in your home directory 3 log43 xml in the installation directory renew2 4 3 config 4 log4j properties in your home directory and 10g4j properties in the installation directory renew2 4 3 config If both files exist individual settings in the user file take precedence over settings in the installation file 5 A failsafe setup with a simple console logger is used if all configuration files are missing Renew provides the logs home property that can be referred from within the configuration files This property by default points to the directory renewlogs in your home directory but you can override that setting with the D option on the java command line Default configuration The default configuration file renew2 4 3 config log4j properti
141. hat an output arc expression for a typed place must be typed In practice this means that you have to declare your variables as soon as you assign types to places On the other hand you can type the variables without having to type the places 43 22 2 24 2 x y Zz Z Figure 3 6 The net equality Sometimes it is required to convert an expression of one type to an expression of a different type Reference nets support Java s concept of casts A cast is indicated by prefixing an expression with the desired type enclosed in parentheses E g Object string would be an expression of type Object even though it will always result in string which is of type String On the other hand if you know that a variable o of type Object will always hold a string you can say String o to inform the type system of this fact For primitive types a conversion takes place e g byte 257 converts the 32 bit integer 257 into the 8 bit integer 1 by truncating the most significant bits In Fig 3 5 we also illustrated that you can make multiple inscriptions to a single transition as we have two guards for a single transition If multiple transition inscriptions are given in a single graphical figure as in this case the inscriptions have to be separated by semicolons They may also optionally be terminated with a semicolon 3 4 3 The Equality Operator If we look at the new semantics of variables we might wonder what the meaning of the opera
142. have to set the property de renew gui shutdownOnClose to true The property de renew gui autostart automatically starts the editor without the need for an initial gui command when set to true The combination of these two gui properties frees users of the pure graphical editor of most complications introduced by the plug in system 2 7 4 Commands As mentioned in Section 2 4 the plug in system needs an initial command to start some plug in Any plug in can provide such commands although the gui command is the one that you will use most of the time In the following we present the basic commands provided by the plug in manager itself and some additional commands provided by other plug ins Note that it is also possible to define a chain of commands by separating the commands with Most 25 of the commands presented here you will typically not use on Renew start up but rather in combination with the Prompt plugin described in the following Section 2 7 5 A basic set of commands is provided by the plug in manager itself help prints a list of all available commands Due to the addition or removal of plug ins this list may vary from time to time get prints the value of a property The property name has to be given as an argument a shows all known property keys set sets the value of a property as explained in Section 2 6 1 This command accepts multiple arguments of the form key value It is important that no spaces are inclu
143. he file renew properties 2 in the installation directory renew2 4 3 config or the file renew properties note the initial dot in your home directory The former configures the Renew 16 installation while the latter provides configuration on a per user basis The user set tings may override installation wide values In the following the text renew properties refers to both files The location of your home directory depends on the operating system for Windows it even differs between versions If you do not know where it is just run Renew The first two lines of the application log that is usually printed to the Java console tell you where Renew expects the configuration files One note for Windows users The Explorer will not allow you to create a file name with an initial dot But you can create such a file via the command line interface DOS window and then edit it as usual In the renew properties file you can for example add the line de renew simulatorMode 1 and Renew uses the sequential simulation engine by default on every run Of course values taken from the renew properties file can always be overridden by a D command line option at startup A template for a renew properties file can be found in the doc directory of your Renew installation At runtime A third way for some not all of the configuration options is provided by menus or dialogues in the net editor To stick with our example the dialog opened
144. he present time We would be very glad to receive experience reports so that the code can become more stable In order to run Renew on a multiprocessor hardware you need a Java implementation that supports native threads Note that there exist Java implementations that support only so called green threads which cannot exploit hardware parallelism You must then set the property de renew simulatorMode to the number of concurrent simulation threads you want Note that it will usually be detrimental to performance if you configure a number of threads that exceeds the number of physical processors Before using multiple processors you should probably try to optimize performance with other means You should configure Log4j to discard log events alternatively you can disable the generation of trace events for all or most net elements You should open only very few net instance windows so that the graphical representation of the markings does not need to be updated Renew This property is evaluated each time a simulation is started It can also be configured 2 0 in the Configure Simulation dialog see Section 4 4 6 If you configure a negative number for the property de renew simulatorMode sequential simulators are used instead of the default concurrent one Although Renew will do that it is kind of weird to configure multiple concurrent instances of the sequential simulator Only the special case of exactly one sequential simulator is of use an
145. he token list does not fit into the current marking window the scroll bars can be used For each different token value in the multiset a current marking window shows the multiplicity if different from one and the value itself The Expanded Tokens mode described in Subsection 4 4 5 is now the default mode for current marking windows if the fs plug in is installed There is a special function to gain access to other net instances If a token s value is or contains a net instance a blue frame appears around the name of the net instance If you click inside that frame a new net instance window for that net instance is opened or the corresponding net instance window is activated if it already existed This also works for net references contained within a tuple or even within a nested tuple Using the Expanded Tokens mode this also works for net references contained within a list or inside any other Java object A You can open a net instance window double click all places you want to watch and Y close the net instance window again This helps to focus on the state information you really want to see 4 5 3 Simulation Control In a concurrent system many transitions can be activated at once Normally the simulation engine decides which of these transitions actually fires when the next simulation step is executed For debugging and testing it can be very convenient for you to take care of this decision Of course this only makes sense when
146. ill be extended by a new transition and a new place The connected arcs are treated in the same manner as described above outbound arcs are reconnected to the new place Coarsen subnet This command coarsens place bounded or transition bounded subnets It is only available if a place bounded or transition bounded subset of figures is selected within the drawing On execution if the selected subset is place bounded all places are merged into one and all transitions are removed The inscriptions of the removed places are attached to the single remaining place All arcs entering or leaving the selected subnet are reconnected to this place too If the selected subset is transition bounded transitions are merged and places are removed respectively Trace This menu and the next two are realized as figure attributes that can be applied to each single net element However they must be set before the simulation is started to take effect They also cannot be applied to figures in net instance drawings Sometimes the simulation log becomes very complex and full To reduce the amount of information that is logged the trace flag of net elements can be switched off e If a transition s trace flag is switched off the firings of this transition are not reported in the log window e A place s trace flag determines whether the insertion of the initial marking into the place should be logged e Ifanarc s trace flag is switched off the messag
147. important internal algorithms and data structures of Renew 2 9 6 Changes in Version 1 5 1 Modifications This was a maintenance release that provided bug fixes for the simulation engine 2 9 7 Changes in Version 1 5 2 Modifications This was a maintenance release that provided bug fixes for the install scripts and a perfor mance improvement of the simulation engine 2 9 8 Changes in Version 1 6 Modifications Java 1 2 is now required for compiling and running Renew Bugs in the Java net parser class loader and simulation engine were fixed Shadow net system serialization and rendering has been fixed The windows menu is sorted alphabetically Windows can be de iconified Additions A remote layer allows the separation of the user interface from the simulation engine A net loader allows on demand loading and compilation of nets during a simulation A new transition inscription manual was introduced for transitions that are not supposed to fire automatically in ordinary running simulations 2 9 9 Changes in Version 2 0 Removals The RenewMode interface provided by the GUI has been removed In consequence the start scripts for the modes disappeared too The channel name and isolated node checks have been removed from the Net menu because they need to be adopted to the new simulator architecture 31 Modifications Java 1 4 is now required for compiling and running Renew The application was decomposed into several plug ins
148. in Version 1 5 2 0 0 0 0 0000 eee eee 31 A ae eee oo oe Be 31 2 9 9 Changes in Version 2 0 0 0 0 0000 eee ee 31 2 9 10 Changes in Version 2 0 U o 32 2 9 11 Changes in Version 2 1U e 32 2 9 12 Changes in Version 2 1 U 0 00000 eee eee 33 rs adds a de ee A 33 A Sewers hee ee eas 34 2 9 16 Changes in Version 2 4 1 2 9 17 Changes in Version 2 4 2 2 9 18 Changes in Version 2 4 3 9 Calling Nets from Java o 52 3 9 1 Net Methoda 0 0 0 0000 a 52 3 9 2 Event lListenea oaoa a 54 3 9 3 Automatic Generation oa eaa e a a 56 3 10 Additional Arc Types 58 3 10 1 Flexible Arcd ee a a a EEUE E e A o aaa 58 3 10 2 Clear Arcg i i sag cack Be a we ae ee o e d 60 a a a ts de dd beeen eae 61 e es a eh soe a ee dada ente ee aa 62 a 12 Pitta a a a de a ae epee i ae a Woke Bee eh 64 o a bok ec eeu 64 A A ah oy oe 64 a dl ae e e ER ee a arn 65 A AE detal eto wl Oh fa Ze oes eae 65 Dar dr Ee ewe aoe a a Aided id ded and 65 12 6_Net Stubg PARA 66 T ata E E ad 66 3 12 8 Case of Class and Variable Names in Untyped Netg 66 AA A nn eee hen eee oo 67 eae eee eee eee ea ee ee 68 gsi does feces eds sy PN Sa ert eee ee oe Ge Ghee a ees cee daa 69 4 3 1 The Selection Tod 69 4 3 2 Drawing Toolg 2 ee 70 4 3 3 Net Drawing Toolf 2 2 ee 75 bie A hee eink ee re oe a ek a 78
149. ing to happen There are situations where a transition cannot be fired manually although it is activated This is the case for all transitions with an uplink Since a transition with an uplink is waiting for a synchronization request from any other transition with the corresponding downlink Renew cannot find such backward activations You have to fire the transition with the downlink instead You should experiment with the simulation mode using some of the sample net systems first Then try to get your own reference nets to run and enjoy the simulation 4 6 Simulation Server Renew supports client server simulations via RMI You can set up a simulation as a Java VM of its own You are then able to connect both locally and remotely as long as the connection between the computers allows RMI calls e g no firewall blocks them Renew As a consequence of the decomposition of Renew into several plug ins any simu 2 O lation can be published over RMI You just need to set the appropriate properties as explained in section 2 6 9 or use the Configure Simulation dialog see sec tion 4 4 6 Therefore this section does not focus on the configuration of a remote simulation it just describes how to set up a simulation without using the editor s graphical user interface To do this you have to export all required nets as a shadow net system first see 4 4 1 for details Whenever you make changes to any net of this net system you have t
150. ingle Renew application This is really a nice feature because it offers a rudimentary operation system integration Renew With release 2 4 the loadrenew script starts a regular Renew instance if the con 2 A nection to a Drawing Load Server was not possible So this script can be used as default command to load Renew 2 6 3 Eager Simulation For very simple nets the simulator can outrun the graphical display This used to lead to a lot of flickering after a continuous simulation run had already been stopped To avoid this behavior we have added a flow control algorithm that delays the firing of the next transition when the GUI gets too slow Because this flow control can slightly slow down the simulation we provide the following switch When setting the property de renew eagerSimulation to true the previous be havior will be restored and the simulator will run at maximum speed Use this switch only when you encounter a real need Renew This property is evaluated each time a simulation is started It can also be configured O inthe Configure Simulation dialog see Section 4 4 6 18 2 6 4 Multiprocessor Mode Renew provides support for shared memory multiprocessors Depending on your specific application and hardware this can significantly speed up the simulation engine But note that this feature is still experimental and has not been tested across platforms due to lack of funds It should not be used for critical applications at t
151. input and output arc variables is established by the transition inscription x xx The rightmost transition has a guard that ensures that x y written guard x y Therefore it can only take a 2 out of the upper place and a 4 out of the lower place or vice versa Action inscriptions are expression inscriptions preceded with the keyword action Con trary to expression inscriptions action inscriptions are guaranteed to be evaluated exactly once during the firing of a transition Action inscriptions cannot be used to calculate the bindings of variables that are used on input arcs because input arc expressions must be fully evaluated before a transition can fire However action inscriptions can help to calculate output tokens and they are required for expressions with side effects Then there are creation inscriptions that deal with the creation of net instances see Section B 6 and synchronous channels see Section B 7 But first we will look closer at the expression syntax which is very similar to a subset of Java In fact we have to look carefully to spot the differences 38 boolean boolean values true false byte 8 bit signed integers short 16 bit signed integers int 32 bit signed integers long 64 bit signed integers char 16 bit unsigned Unicode characters float 32 bit IEEE floating point numbers double 64 bit IEEE floating point numbers Table 3 1 The primitive data types of Java 3 2 Ido not Want to Learn Java Even if y
152. instances of a class They have an identity that can be checked with and just like objects They have a state that can change over time and here places seem to correspond to attributes Net instances also encapsulate data They can be referenced from other net instances The only missing com ponent for full objects are methods In the next section we will learn about a communication concept that can be substituted for method calls sometimes In Sec 3 9 we will finally see how nets can be equipped with methods 3 7 Synchronous Channels Currently the idea of net instances might not seem interesting because there is no mechanism by which nets can influence each other Hence although net instances encapsulate data they encapsulate it so well that it cannot be accessed at all In this section we will establish a means of communication for net instances There are two fundamentally different ways of communication First we have message passing where a sender creates a message that can be read by a receiver later on The sender can always send the message regardless of the state of the receiver The receiver may or may not be able to process the message Second we have synchronous communication where sender and receiver have to agree on participating in an communication at some point of time In Petri net formalisms the former kind of communication is usually captured by so called fusion places Reference nets though implement the latter ki
153. into Renew To conclude we still encourage some brave people to write system specific Drawing Load Clients e g in C and make them available for the next Renew release All you need is such a simple client application that opens a socket to the server using the same port number as above transmits its parameter and closes the socket again Our Java client is started by this example is again given in Unix syntax the is used to indicate that the three printed lines should be combined into one command line java Dde renew loadServerPort 65111 cp plugins libs log4j CH ifa draw application DrawingLoadClient lt file name gt where 65111 is an example for the port number on which the server is running if you decided to configure the property in the renew properties configuration file the D part of the command can be omitted Renew Alternatively you can use the script loadrenew provided by the installation process 2 0 1 to invoke this Java application This script did not work in release 2 0 but has now been fixed It is provided for Windows and Unix The script uses the port configured in the renew properties file If you want to use the Drawing Load Client the idea is to associate the corresponding script to the RNW extension and start Renew once manually When a drawing is double clicked in the file manager the client is invoked and can transmit the drawing s file name which is then received and loaded by the s
154. ion rnw e g renew MyNet rnw some where OtherNet rnw On start up Renew tries to load drawings from all specified files On Unix systems you can even use renew some where rnw to load all drawings in a directory If you have a program icon that is associated correctly your OS usually also supports double clicking some rnw file or using drag amp drop In the rare case that Renew terminates abnormally it should leave an autosave files for each modified net drawing Autosave files are typically updates every two minutes You can detect an autosave file by its file extension aut Whenever possible the filename is derived from the main drawing s file name by removing the old name extension rnw and adding aut If such a file exists already a random file name of the form rnw99999 aut with an arbitrary number is chosen In order to recover an autosave file simply rename it so that it receives the rnw extension Renew also leaves bak files that constitute the last version of the file that Renew loaded Unlike autosave files these files are overwritten during subsequent runs of Renew 4 3 Tools In the toolbar several tool buttons are displayed which can be selected by clicking on them The tool buttons are grouped in two or more toolbars depending on the mode of Renew When resizing the Renew window toolbars are wrapped according to the size of the window The standard toolbars are the drawing toolbar and the Petri net t
155. ions in the previous section but replace any reference to renew2 4 3 loader jar by renew2 4 3 src dist loader jar The plugins directory is relocated from its distribu tion position to renew2 4 3 src dist plugins too If you succeed to run the compiled Renew you can delete the file renew2 4 3 loader jar and the directory renew2 4 3 plugins with the original class files You should then con sider to edit the start scripts for your platform so that they become aware of the file location changes Please note that the clean target defined in the Ant build xml file completely removes the renew2 4 3 src dist directory tree Therefore any modifications like installed plug ins made in that directory tree get lost every time you run ant clean 2 5 Platform specific Hints For a few platforms we provide special installation support Even in these cases you could install Renew as described above but your task will be easier if you read this section The installation script is typically called installrenew or similar Start this script to install Renew The script will create the actual startup scripts for Renew You have to start the one called renew or similar to get the basic version of Renew running Other scripts allow you to load drawings into a running Renew editor or provide help for the generation and compilation of stubs as summarized in Table 2 1 In the next subsections we will only describe the usage of the basic script The other sc
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157. ke the previous item the breakpoint occurs at the end of a transition s firing This is especially useful in the case of net stubs where you want to inspect the result of a stub call e Marking changes Any change of the state of a place is detected here even if the change is simply due to a test arc e Marking changes ignoring test arcs Here it is required that tokens are actually moved and not merely tested e 1 token Only a token deposit triggers this breakpoint e 1 token A token removal must occur before this breakpoint is activated e Test status changes Normal arcs do not trigger this breakpoint but test arcs do Multiple breakpoint types may be set for a single net element using this menu Clear Breakpoint at Selection A breakpoint is not automatically cleared after it was invoked Instead you must clear breakpoints explicitly Having selected the net element that contains a breakpoint you can either clear all local breakpoints or all global breakpoints 101 Clear All Breakpoints in Current Simulation This command will get rid of all break points that were ever set This is useful if you have reached a certain desired situation and want to continue the simulation normally Alternatively you might want to clear all break points that were configured using the attribute menu if you require a completely automatic run once in a while but not want to loose the information about the standard breakpoints Breakpoint
158. l components except FS The package is no longer distributed with the base archive but included in the FS plug in 2 3 5 Upgrade from Renew 2 1 2 1 1 or earlier The required Java version has changed you need at least Java 1 5 to run newer versions of Renew Saved simulation states exported by Renew 2 1 1 or earlier cannot be used with the current version of Renew The Drawing Load Server see 2 6 2 now accepts connections from the local loopback interface only this has been introduced as a security measure The JUnit test classes that were sparsely scattered in the Renew code have been migrated from JUnit 3 x to JUnit 4 x architecture 12 2 3 6 Upgrade from Renew 2 2 or earlier The required Java version has changed you need at least Java 6 to run newer versions of Renew 2 3 7 Upgrade from Renew 2 3 or earlier Files exported to the experimental xrn format cannot be used anymore Its support has been discontinued We encourage the use of PNML instead 2 4 Installing Renew The two zip files renew2 4 3base zip and renew2 4 3source zip form the standard Re new distribution While the former file contains all files that are required for the operation of Renew the latter file includes the source files which are generally not needed unless you intend to modify Renew or learn about its algorithms In addition to the base distribution we provide some plug ins at our web page The base Renew distribution consumes about 5 MByte The
159. le Typically all tokens are also immutable value objects which acquire their state once during creation before these objects are used as tokens in the net For value objects the equals method must not be based on object identity but on the represented value Similarly the hashCode method must also be properly defined If you use mutable stateful objects in your nets you must observe further restrictions Contrary to value object stateful objects must preserve the original implementations of Object equals and Object hashCode Furthermore the stateful objects must either occur directly as tokens in the net or there must be exactly one token by which a given stateful object is reachable Failure to do so will result in a corrupted simulation state when restoring the simulation from the database There is no garbage collection when using the database backed simulation 2 6 9 Remote Simulation Access Renew Any Renew simulation regardless whether it is started from the command line or 2 O within the graphical editor can be published via Java s Remote Method Invocation RMI technique Any Renew editor can then connect to the published remote simulation display the token game and control the firing of transitions See Section 4 4 6 about how to connect to a running remote simulation This section focuses on how to configure the simulation engine for remote access 22 The first step is that you start an RMI registry on the m
160. le that a single synchronization transfers information in both directions Fig 3 14 shows a possible application where the left transition consults a lookup table that is managed by 49 i foo bar this bar this bar this foo Figure 3 13 The net multi 49 this lookup x y OM lookup a b 42 6x7 E 56 8x7 y a b Figure 3 14 The net param the right net instance The parameter lists x y and a b match if x a and y b After binding x from the left place the variable a is determined and only one token of the right place matches the tuple of the arc inscription This allows to bind b and hence y In the previous examples we only encountered local synchronizations within one net but Figs 3 15 and 3 16 show two separate nets that can communicate The net represents the basic schedule of Santa Claus on the night before Christmas He wakes up takes a new bag from the shelf and fills it with presents Later on he can simply reach into his bag and get something that he can put into the children s boots maybe some candy or a brand new game l wakeup boots b new bag deposit thing l b deposit sweets thing take thing b deposit token game thing thing bag b take thing Figure 3 15 The net santa Figure 3 16 The net bag It is possible to create synchronization loops where the invocation of a channel results in the invocation of the same channel This should be avoided be
161. les 2 1_ The startup and stub scripts 3 1_ The primitive data types of Javal 4 1 Summary of selection tool operations 32_ Java binary operators rules separate operators of equal precedence 2 2 Properties to configure database backidgl 2 3_ Properties to configure a remote simulatio Chapter 1 Introduction On the following pages you will learn about Renew the Reference Net Workshop The most important topics are e installing the tool Chapter B e the reference net formalism Chapter B e using Renew Chapter Both reference nets and their supporting tools are based on the programming language Java To be able to use them to their full capacity some knowledge of Java is required While the basic concepts of Java will be explained in this document there are plenty of books that will serve as a more in depth introduction to Java 19 is a good first start for experienced programmers If you encounter any problem during your work with Renew we will try to help you See Appendix A for our address At the same address you can make suggestions for improvements or you can request information on the latest release of Renew If you want to submit example models or extensions to the tool that would be especially welcome 1 1 Should I Use Renew The main strength of Renew lies in its openness and versatility e Renew has been written in Java so it will run on all major mo
162. llipse Tool The ellipse tool works the same way as the rectangle tool see above only that ellipses are created within the given rectangle area An ellipse figure has the same handles as a rectangle figure The Pie Tool Renew The pie tool works the same way as the rectangle tool see above only that segments 2 2 of ellipses are created within the given rectangle area A pie figure has the same handles as a rectangle figure with two additional angle handles that are small yellow circles The angle handles control start and end of the arc segment that frames the pie By pressing the control key while dragging these handles around their movement can be restricted to steps of 15 degrees If a pie s fill color is set to none it displays as an open arc segment instead of a closed pie The Diamond Tool The diamond tool works the same way as the rectangle tool see above only that diamonds are created within the given rectangle area A diamond figure has the same handles as a rectangle figure The Triangle Tool The triangle tool works the same way as the rectangle tool see above only that triangles are created within the given rectangle area A triangle figure has the same handles as a rectangle figure with an additional turn handle that is a small yellow circle This handle lets you choose the direction the triangle points to which is restricted to one of the centers of the four sides or one of the four corn
163. lly be written in some future release packageCount prints the packages and the total number of packages in the class loader exit terminates the plug in system and in consequence the whole application If some plug in hangs during termination you can use exit force to kill the Java VM abruptly gc triggers the Java garbage collector script loads commands from a text file and executes them The file name has to be given as argument it can be specified relative to the current directory This command is especially useful as initial command when you in fact need to issue several commands at startup of the plug in system The following commands are not provided by the plug in manager but by some Renew plug ins So they are available only when the respective plug in is loaded gui starts the graphical editor and or passes its arguments to the editor The arguments are supposed to be drawing file names This command is provided by the Gui plug in 26 demonstrator opens a window with a list of drawing file names This plug in is provided by the Gui plug in ex exports a drawing into various formats The usage of the command is export lt extension gt lt drawing gt where lt extension gt may be pdf eps svg png and lola This com mand is provided by the Export plug in which in turn uses the FreeHEP project for graphical exports startsimulation starts a simulation without using the graphical editor See Section 4 6 This command
164. ly from a simulation started by the editor The net loader does not look for rnw files it loads nets from sns files only If you want to experiment with properties and commands or if you need to pause and run the simulation interactively you should install the prompt plug in see section 2 7 5 When a simulation is running several commands can be entered at the prompt to control the simulation These commands provide the same functionality as the menu entries listed in section 4 4 6 In fact if you use the prompt plug in in combination with the graphical editor both command sets menu and console control the same simulation The console commands are simulation run Resumes a stopped simulation If the i option was appended to the startsimulation command this command starts the simulation simulation step Executes another simulation step If the i option was appended to the startsimulation command this command executes the first simulation step simulation stop Halts the simulation but does not abandon it despite of the term com mand The run command continues it This is equivalent to the menu entry Halt simulation simulation term Ends and abandons the current simulation This may result in termina tion of the plug in system see section 2 7 3 simulation help Shows a short help for all available simulation commands 4 7 Error Handling Renew helps you to maintain a syntactically correct model by making an immediat
165. me Maybe you forgot an import statement in the declaration node No such class or variable The meaning of a name could not be determined at all Maybe the name was misspelled Maybe a declaration or an import statement is missing No such constructor A matching constructor could not be found Maybe the parameters are in the wrong order Maybe the number of parameters is not correct Maybe the requested constructor is not public No such field A matching field could not be found Maybe the name was misspelled Maybe the requested field is not public No such method A matching method could not be found Maybe the name was misspelled Maybe the parameters are in the wrong order Maybe the number of parameters is not correct Maybe the requested method is not public Renew For errors of type No such constructor field method proposals for correct construc 2 3 tors fields or methods are provided by the syntax check If a constructor with the wrong number or types of arguments is entered a list of existing constructor signa tures is provided If a non existing field name for a class or an object is entered a list of all known field names is provided If a non existing method is entered a list of known method signatures where the method name is prefixed by the erroneous 109 method name is provided If the method name is entered a list of all known methods is provided No such variable A name that supposedly denotes a
166. ments the net component in convenient way Weak means that although the net component can be moved by clicking and dragging the mouse in between the net elements they can each individually be manipulated Individual net elements can be dragged resulting in a manipulated layout of the net component It is also possible to edit inscriptions of elements belonging to the net component Flat means that grouping is not hierarchical In order to provide the functionality a new Figure has been added which has no graphical representation of its own The Net Component Plugin provides two basic functionalists The grouping and ungroup ing of a selection of net elements and the management of tool palettes which represent a repository of pre defined sets of net components A repository consists in a folder that holds several Renew net drawings an images folder and a configuration file sequence The images folder should contain icons in gif format 24x24 pixels which are used to fill the tool buttons of the palettes If no image is defined for a specific net component a generic image generic gif will be used instead Names of net drawings and icon images should correspond The sequence file contains the names of the drawings without extensions and define the sequence in which the buttons are shown in the palette The file may be empty but has to be present in order for the directory to be recognized as net component repository Further non listed dr
167. menu where additional loggers can be added The logger name serves as filter criterion Each logger can be configured to send its data to one or more appenders Depending on the kind of appender the filtered simulation trace can go to the console a file or a trace window GuiAppender Each appender can be configured with various options For example the buffer size the number of viewable simulation steps of the GuiAppender can be adjusted to your needs Renew The textfield Layout is used to customize logger output using log4j PatternLayout 2 4 Remote server Using this menu entry you can list all net instances of a Renew simulation server To be able to do this a simulator must be running with remote access enabled as described in section 2 6 9 The dialog comprises two parts The upper buttons switch between remote simulations the lower part shows a list of net instances Initially the list shows net instances of the local simulation if there is a running simulation The Connect button displays another dialog which allows you to connect to a remote simulation server You must specify the host on which the Server is running The server Name can be left at the default value unless you specified the de renew remote publicName property on the server side If the connection has been established the drop down box at the top of the Remote Renew servers dialog includes the remote simulation and the list of net instances is update
168. minate until the simulation step needed for the involved channel synchronization is completed The simulator may hang if stub methods are executed outside of actions This note applies especially to those cases where a net calls a Java method which in turn calls a net stub 3 12 7 Execution of synchronized Java Code This comes close to the execution of methods with side effects The side effect of a synchro nized method or code block is that it delays the execution of other threads This can lead to a deadlock when the thread of the simulation engine has to wait in a monitor for another thread which cannot finish without the simulation thread if you are asking how to produce such a constellation Call a net stub from synchronized code for example There are two ways how to avoid the problem e Do not use synchronized Java code Every time you would need synchronization model it explicitly with nets This way you are able to see the problem if one occurs e When calling a synchronized method make the calling inscription an action inscrip tion So the simulation engine is out of danger of waiting in a Java monitor during the search for bindings If you are using the default concurrent simulator it stays alive and is able to continue its work It still can happen that the execution of the action inscription hangs but then the responsible transition is highlighted and can be identified 3 12 8 Case of Class and Variable Names in Untyped N
169. n bindings can be selected and fired under user control The multiset of tokens contained in a place instance can be displayed as just the cardinality of the multiset a collection of all tokens in the multiset directly within the drawing or in a separate window Individual components of tuples can be inspected Initial markings are hidden during the simulation 2 9 2 Changes in Version 1 2 Modifications The simulation engine was made more robust and flexible Minor bugs were fixed A single inscription figure may now contain multiple arc inscriptions or initial marking inscriptions that are separated by semicolons Slight inconsistencies in the inscription lan guage were cleaned up The type rules were improved The results of action inscriptions may now be passed through synchronous channels even in the presence of typed variables Some display problems with Java 1 2 have been fixed Additions Flexible arcs were added Clear arcs were added Inhibitor arcs were added Marked places and firing transitions can now be highlighted during the simulation A rudimentary net layout algorithm has been implemented The state of a running simulation can now be saved and restored Restarting a simulation may now reload Java classes Export of Encapsulated PostScript was implemented Selection of groups of figures was improved 2 9 3 Changes in Version 1 3 Modifications Some minor improvements of the graphical user interface were applied Ad
170. n of unzip If you have a version of the JDK that does not support zipped jar archives please let us know 28 Note that you must use Java 1 1 or newer to use jar archives and that Renew requires Java 1 7 for different reasons anyway e Java is not found Probably the shell scripts try to look for Java in the wrong places e Under Windows the installation or the start of Renew terminates with a message regarding missing space for environment variable Enlarge the environment space for the command window e Java cannot find the class de renew plugin Loader This should not happen if you use jar renew2 4 3 loader jarat the Java command line If you want to use the environment variable CLASSPATH instead check if it includes loader jar e Renew starts but the window titles are incorrect under the X Windows System Try a different window manager e g mwm is known to work correctly This is a general Java problem and not related to Renew so we cannot do anything about it e When I switch to a window of a different application while the Renew menu is open the menu stays visible in front of all other windows This is a general Java more concrete Swing problem and not related to Renew so we cannot do anything about it With Java 1 5 the bug has been fixed e I cannot open the sample files Sometimes you need to add the root directory or depending on your operating system to your class path e Under Mac OS X usi
171. nd of communication in the form 48 of synchronous channels This allows more expressive models compared to message passing because it hides much of the inherent complexity of synchronization from the developer Furthermore message passing can always be simulated using synchronous communication Synchronous channels were first considered for colored Petri nets by Christensen and Damgaard Hansen in 5 They synchronize two transitions which both fire atomically at the same time Both transitions must agree on the name of the channel and on a set of parameters before they can engage in the synchronization Here we generalize this concept by allowing transitions in different net instances to syn chronize In association with classical object oriented languages we require that the initiator of a synchronization knows the other net instance The initiating transition must have a special inscription the so called downlink A down link makes a request at a designated subordinate net A downlink consists of an expression that must evaluate to a net reference a colon the name of the channel an opening parenthesis an optional comma separated list of arguments and a closing parenthesis E g net ch 1 2 3 tries to synchronize with another transition in the net denoted by the variable net the channel has the name ch and is passed the parameters 1 2 and 3 On the other side the transition must be inscribed with a so called uplink An uplink s
172. nd only simulation 3 All mentioned optional plugins are not part of the release of Renew They are provided separately 104 relevant objects are selectable like current markings of places and transition instances Places in net instance windows are annotated with the number of tokens they contain if any If you double click on a marking the containing place will be selected If you right click on such a marking the marking will switch between the number of tokens and the tokens in a string representation If you right click on the containing place another window appears containing detailed information about the tokens You can display the contents of the current marking directly inside the net instance window This is extremely useful when a place contains only few tokens or even only one This also helps to control the number of windows which could become very large using Renew To switch between the simple cardinality of the multiset and the token display of a place marking just right click it The expanded display behaves exactly like the contents of a current marking window which is described in the following section Renew Tokens in markings are now always displayed with a white opaque background This increases the readability of markings 4 5 2 Current Marking Windows A current marking window shows the name of the corresponding place net instance name dot place name e g myNet 1 myPlace in its window title bar If t
173. net sns files and automatically load compile and include them into the net system The net loader is configured using the property de renew netPath where the value is a list of directories specified in the same syntax as the CLASSPATH environment variable used by Java Currently the net path can comprise directories only jar or zip files are not supported Subdirectories of the given directories are not searched either The order of directories in the path list matters the first directory containing a net will be used Renew Jt is now possible to specify netpath directories relative to the classpath This is done 2 0 by prepending the directory entry with the reserved directory name CLASSPATH For example if you include the directory in Unix syntax Windows users should re place the slash by a backslash CLASSPATH nets in the de renew netPath property then the net loader would look for a missing net file throughout all nets directories relative to all classpath entries The searched classpath includes everything from the Java system classpath all loaded plug ins and the de renew classPath property see Section 2 6 6 in that order When they are included in the classpath jar and zip files are searched too The behavior of the net loader differs depending on the type of file it finds when looking for a net If it encounters a shadow net system sns file the net will be loaded into the simulation or used for a syntax check
174. new By setting the property de renew classReinit to true you can request that all user classes that are referenced by a net are reloaded before every compilation of a net When the class reloading feature is enabled the de renew classPath property is re read at each simulation setup but changes to the classpath do not affect the plug in system However there is a nasty caveat with this feature Even without changing the class path you can have two instances of the same class in the Java VM Both are loaded from de renew classPath but one is known to the plug in system while the other one is known to the current simulation only These classes are never identical or equal if they are compared for example when the instanceof operator is applied to an object of the other class Note that this mechanism may result in some problems when you access the Java reflection API too This property can also be changed from the Configure Simulation dialog see Sec tion 4 4 6 It is evaluated each time a simulation is set up If no simulation is running the graphical editor evaluates it before each compilation Because the reloading of classes might affect performance it is disabled by default 2 6 7 Net Loading When you are using many nets referencing each other you might want to try the net loading mechanism When nets are missing during a syntax check compilation or simulation the 20 engine will look for matching drawing rnw or shadow
175. ng cmd Q apple Q to quit the application will not give you the opportunity to save changes even if the document has recently been modified Renew The optional AppleUI plug in see Section 2 5 1 solves that problem 2 0 1 2 9 History Version 1 0 was the first public release It included a net editor a reference net simulator a Java stub compiler and example nets 2 9 1 Changes in Version 1 1 Modifications Some performance enhancements were implemented and minor bugs were fixed Some source level inconsistencies were cleaned up The thread model of Java 1 2 was adopted The source code was changed to be compilable with Java 1 1 3 The windowing code was made more robust under Java 1 2 The handling of nul1 objects in the simulator was corrected The type system was made more compatible with the Java type system The trace flag of netelements is now saved to disk The simulation performance was improved The garbage collection of net instances was improved The graphical user interface was improved for some window managers The presentation of current markings was improved The interactive execution of reference nets has been improved a lot see Section 4 4 6 29 Additions The parallel simulation code was added The checks for double names and for cyclic channel dependencies were added Transition inscriptions may now include several parts separated by semicolons Virtual places may now be used in nets During the simulatio
176. ns are set in plain style while labels text without semantic meaning are italic The syntax of an inscription is checked directly after you stop editing it see Section 4 7 Refer to Chapter B for a description of the syntax of Renew net inscriptions The Name Tool The name tool also connects text to net elements in this case to places and transitions only By default a name is set in bold style The idea of a name for a place or transition is to enhance readability of the net as well as simulation runs When a transition fires its name is printed in the simulation trace exactly like you specified it in the name figure Place names are used in the simulation trace whenever tokens are removed from or put into a place Also a place s name is used in the window title of current marking windows and a transition s name is used in the new transition binding window see Section 4 4 6 Each place and transition should have at most one name figure connected and each name should be unique within one net but the editor does not check either of these conditions Places and transitions without connected name figures are given a default name like P1 P2 and T1 T2 The Declaration Tool A declaration figure is only needed if you decide to use types see Section 3 4 2 Each drawing should have at most one declaration figure The figure is used like a text figure only that the text it contains has a semantic meaning to the simulator The tex
177. nsition perform This way the juggler only starts his business when there is at least one spectator 3 10 3 Inhibitor Arcs Inhibitor arcs make sure that a token of a certain kind is not in a place They are used to represent boolean conditions with simple black tokens when it is required to check for the inverse condition too They are also used to delay certain actions until a system is idle and to wait until the end of a loop In order to use this arc type you need to select the extended sequential mode as described in Subsection 2 6 5 Some varieties of inhibitor arcs were suggested in the literature see 6 and 13 for a recent approach and 4 for a consideration of concurrency issues The papers also give further references The formalism presented here is less general than that presented in 6 but on the other hand we do not require that the place associated to the inhibitor arc is bounded by a capacity An inhibitor arc is represented by a connection with a filled circle on each end in Renew 61 money newmoney arrive waiting Xx perform action newmoney money 5 x length Figure 3 27 The net juggler unknown O Figure 3 28 The net filetypes Some other formalisms highlight only one of the line s ends but we prefer the symmetric appearance because it emphasizes that no changes to the current marking are performed by inhibitor arcs An inhibitor arc may be inscribed just like an ordinary input arc
178. nt this deposit amount Figure 3 18 The net account 3 9 Calling Nets from Java In the previous section we considered the use of a Java like inscription language in reference nets Now we are going to allow access to reference nets from Java code Nets are already objects and they have an identity But up to now all nets have the same type namely de renew net NetInstance and implement the methods of de renew net NetInstance only 3 9 1 Net Methods Therefore we must create new classes that behave like nets when treated by the simulator but which implement additional methods Upon invocation the methods can communicate with the net through synchronous channels which will in turn take the required actions These classes will be known as stub classes The net from Fig 3 18 models a very simple bank account The customer can only deposit and withdraw money and view the current amount But we still need to wrap the synchronous channels in methods so that we can use the bank account from Java code There is a special utility that creates appropriate methods automatically We can input void deposit int amount this deposit amount to describe the action associated with this method Not all methods will be so simple e g there might be more than one channel invocation The translator needs to know other things besides the methods especially the name of the net here account and the name of the stub class that should be
179. o generate the shadow net system again and start a new server with it Now you are ready to start the server itself by issuing the following command to the Renew plug in system startsimulation lt net system gt lt primary net gt i The parameters to this command have the following meaning net system The sns file as generated in the step above primary net The name of the net of which a net instance shall be opened when the sim ulation starts Using the regular GUI this equals the selecting of a net before starting the simulation i If you set this optional flag then the simulation is initialized only that is the primary net instance is opened but the simulation is not started automatically As mentioned in section 2 7 the command can be passed to the plug in system by several means For example to start a remotely accessible simulation with net systemnet out of the net system allnets sns direct from the java command line you will have to issue the following command in Unix syntax the indicates that the printed lines should be entered as one line 106 java Dde renew remote enable true jar renew2 4 3 loader jar startsimulation allnets sns systemnet If you need a special simulation mode or any other Renew property to be configured you can add multiple D options or use one of the other configuration methods mentioned in section 2 6 1 A simulation started by the startsimulation command differs slight
180. od this method instance argO argi arg2 this result instance There is one problem with that solution namely that methods should be able to throw exceptions Because exceptions in Petri nets are not very well understood we did not imple ment an exception mechanism right now It might be added in several ways none of which looks entirely satisfying A regular structure of the synchronization requests suggests that we could generate the stub description files automatically This is indeed possible using the Unix shell script makestub that creates a stub automatically The script needs the name of the class to 56 inst new Object hasMoreElements inst result result inst res inst num gt 0 0 inst res num token game 2 socks num 1 inst thing thing num En man O inst num inst new Object nextElement inst guard num gt 0 Figure 3 22 The net enumbag be generated the name of the net that is associated to the class and a list of interfaces that the class should implement For makestub the methods that are to be implemented are given only via the list of interfaces This might seem as a limitation but quite often appropriate interfaces will be present and in other cases they can be defined easily And even in ordinary Java it is often helpful to declare all public methods in interfaces Assume that Santa s quality assurance department determines that the current version of Santa s ba
181. of variables is not well suited for high level Petri nets Instead variables are supposed to be bound to one single value during the firing of a transition and that value must not change However during the next firing of the same transition the variables may be bound to completely different values This is quite similar to the way variables are used in logical programming e g in Prolog In Fig 3 4 we show an example net that uses expressions as arc inscriptions and also as guard inscriptions The example is provided in the directory samples simple Some numbers are put into a place and the net will compute the greatest common divisor of all these numbers and terminate with no more enabled transitions The upper central transition is the most interesting It removes two tokens from the pool of numbers but a guard makes sure that the two numbers are greater than zero and correctly ordered The transition outputs the smaller number and the remainder denoted by the operator of the division of the greater number by the smaller number The lower central transition simply puts the new numbers back into the pool and the left transition discards zeroes Note how a single variable can be bound to different values at different times Note that the simulator will automatically search for possible bindings of the variables 42 guard gt j int guardj gt 0 io int a a int i int j Figure 3 5 The net gcdtyped 3 4 2 Types For referenc
182. og can be used to copy color attributes between figures by a sequence of Y Update and Apply actions Similar dialogues are provided for other attributes like pen color text color font and font size Opaqueness Renew The opaqueness attribute determines the transparency of the inner area of a figure 2 2 of the pen color or of the font Each attribute Fill Color Pen Color and Font has its own opaqueness menu that is located right below each menu entry The visibility of each item can be set in values ranging from 0 invisible to 100 opaque j The transparency attribute is ignored in Postscript or EPS export However trans SY parencies are printed correctly using the Print dialog and in the PDF SVG and PNG export formats Pen Color The pen color attribute is used for all lines that are drawn All figures but the image figure support this attribute Note that the pen color does not change a text figure s text color see below but the color of a rectangle frame that is drawn around the text Again choose the desired color from the given list The default pen color is black except for text figures where it is None i e transparent The other entry at the end of the list of colors opens a full featured color chooser dialog as described under Fill color Visibility The visibility attribute can be used for all types of figures A figure marked as invisible is still part of the drawing but it will not be displayed As it is no
183. on process It is not difficult especially if you are already at ease with the Java environment But even as a novice you should be able to complete the process successfully 2 1 Prerequisites Before you proceed make sure to have a system backup available on the off chance that an error occurs during the installation procedure You must have Java 1 7 or higher installed If you have not done this yet we suggest that you get the latest Java Runtime Environment from Oracle http www oracle com technetwork java where versions for Windows Linux and Solaris are available For Apple Macintosh you can use the Java runtime build into MacOS X as described on http www apple com without any additional installation You need at least MacOS X 10 5 All runtime environments are available free of charge for personal use We recommend the latest version of JDK 1 7 which at this point of time should be JDK 1 7 0 depending on the operating system If you intend to do a source installation you also need to install a couple of software packages from third parties See Section 2 4 2 for details 2 2 Possible Collisions While Renew is based on the JHotDraw package by Gamma 8 the package is distributed with Renew The package has been substantially improved so that it is impossible to substitute a different version for it If you have the original JHotDraw installed this might result in a problem
184. oolbar More toolbars can show up based on the chosen formalism Each single toolbar can be put into its own window by clicking at the spot on the left of the toolbar Figure 4 2 shows the Petri net toolbar in a separate window If a toolbar window is closed the toolbar is returned to the Renew window Petri Net Tools Figure 4 2 The Petri Net Toolbar in its own Window At any point in time exactly one tool of all toolbars is selected which appears pushed down By default a special tool the selection tool is selected whenever the work with the current tool is finished If you double click a tool button the tool will remain active until you explicitly select another tool or right click on an empty spot in the drawing This replaces the menu Toggle Sticky Tools from the Edit menu In general double clicking tools is most useful during the initial creation of nets but there are also other probably more elegant ways and the normal selection is more apt to later modification stages But of course which way to use tools also depends on your personal preferences In the status line in the Renew window a short description of the tool is displayed if you move the mouse pointer over a tool button All other tools but the selection tool are used to create a certain type of figures Some of the tools can also be used to manipulate already existing figures of the corresponding type 4 3 1 The Selection Tool The selection tool is the m
185. or the place instance has to be selected 94 Breakpoints Using this attribute you can request breakpoints for certain places and transitions These breakpoints will be established immediately after the start of the simulation and have exactly the same effect as a global breakpoint that is set during the simulation Renew Inthe net drawing transitions and places with a set breakpoint attribute are marked 2 1 by a small red circle in their upper right corner However the tag is not shown in instance drawings Attributed breakpoints like breakpoints set during the simulation will show up in the breakpoint menu while the simulation is running Please see subsection 1 4 6 for a detailed description of the possible breakpoints Note that you can set at most one breakpoint for each net element using this menu command Attributed breakpoints are established only when the net drawing is loaded in the editor at the moment where the compiled net is passed to the simulation engine For the initial drawings that were used to start the simulation this is usually the case But if nets are loaded later by the net loader from sns files see Subsection 2 6 7 no breakpoints are set This behavior is due to the fact that the responsibility for the creation of breakpoints lies in the graphical user interface and not in the simulation engine Since the breakpoint attribute is dropped when exporting shadow net systems see Subsection 1 4 1 the simul
186. ort for the crn format is discontinued We encourage the use of PNML instead We fixed the remote server connection RMI by providing configuration see the User Guide Section 2 6 We have fixed the simulation database backing and adapted the mechanism for MySQL with InnoDB Remaining AWT dialogues have been converted to Swing The Logging GUI has been improved by decoupling the Simulator from the GUI The loadrenew script now starts a regular Renew instance if the connection to a Drawing Load Server is not possible The desktop integration for Linux and Windows have been improved We provide new unified icons for all operating systems Many minor bugs have been fixed Some of these were e Rare problems with locating nets relative to the classpath have been solved e Changes on the line style now affects all figures e The font style underlined now also affects small font sizes e Export to PNML now always produces files in UTF 8 character encoding e The Logging tab of the Configure Simulation dialog has been revised e The log4j PatternLayout can now be set from within the GUI e Custom file appenders created in Logging GUI are now functional e Net components are more robust if attached figures are manipulated e It is now possible to escape whitespaces in command line commands In that way it is possible to open drawings with whitespaces in the path from command line Additions The Navigator now offers a button to recursively
187. ost basic tool and is not related to any special figure type Instead any figure or group of figures can be selected and moved using this tool If not otherwise noted when talking about pressing a mouse button the primary mouse button is meant If the selection tool is the current tool the following user interactions are possible Select By clicking on a figure it becomes selected A selected figure can be recognized by its visible handles Depending on the type of figure different handles appear but in all cases some handles will appear There are even non functional handles which are just 69 there to show that a figure is selected and do not have any additional manipulation functionality If another figure is selected the current figure becomes deselected To clear the current selection click inside the drawing but not on any figure Add to Selection If the shift key is depressed while clicking on a figure the figure is added to or removed from the current selection depending on its selection status This way a group of objects can be selected which is convenient or even required for some com mands Area Selection If the mouse button is depressed inside a drawing but not inside any figure the area selection mode is activated after a short delay The starting point marks one corner of a rubber band rectangle While the mouse button is held down the other corner of that rectangle can be dragged by moving the mouse When
188. ou do not want to learn Java Renew might be a useful tool for you although it looses some of its expressiveness In many cases it is enough to learn how to write numbers strings variables and the simplest operators Reference nets provide extensions that go well beyond simple high level Petri nets with Java inscriptions After you have read the next sections you can use these extensions to generate complex models without the need to incorporate Java code But remember that there are always subproblems that are easier to express in a program ming language rather than Petri nets Reference nets work together seamlessly with Java programs and gain a lot from utilizing the Java libraries So once you do learn Java you can choose the appropriate modeling method for each task at hand 33 A Thimble of Java If you are already familiar with Java you will want to skip to Section 3 4 where we discuss the differences between Java and the inscription language used in reference nets Here we give a most rudimentary introduction to Java Java is an object oriented programming language but not everything is an object in Java There are eight non object data types in Java which are listed in Table 3 1 The types byte short char int and long are called integral types here Together with float and double they form the number types In Figure 8 3 you can see two type hierarchies On the left the ordinary Java subtype relation is depicted You can see
189. oup offers the typical clipboard interactions Cut and Copy relate to the current selection in the active drawing window see Section 4 2 Thus these functions are only available if there is a current selection 84 Cut puts all selected figures into the clipboard and removes them from the drawing The keyboard shortcut for Cut is Ctrl X Copy puts all selected figures into the clipboard but they also remain in the drawing The keyboard shortcut for Copy is Ctrl C Paste inserts the current clipboard contents into the active drawing The upper left corner of the object or group of objects is placed at the coordinates of the last mouse click The keyboard shortcut for Paste is Ctrl V Note that due to restrictions of Java Renew s clipboard does not interact with your operating system s clipboard The current selection is automatically extended to include all referenced figures before copying to the clipboard If for example you select an arc inscription and invoke copy and then paste the arc the start figure and the end figure of the arc will also be copied This is sometimes not what you intended to do but you can easily move the copied arc inscription to the original arc see Section 4 3 2 and remove the other duplicated figures Of course cut only removes the figures which were originally selected A The better alternative to copy inscriptions is to mark and copy the text of the inscription when you are in text edit mode Ctrl C
190. ove these to an area outside the net This has a similar effect as the current marking window but you do not get your screen cluttered with so many windows 76 The Arc Tools The arc tool works quite the same as the connection tool see description in Section 4 3 2 The differences are like above that an arc has a semantic meaning to the simulator A restriction coming from the Petri net structure is that an arc always has to connect one transition and one place not two figures of the same kind or any other figures The arc will not snap in on the wrong figures and disappear if you release the mouse button over a wrong figure This behavior is different from when you create arcs using the arc connection handle in places or transitions see Section 4 3 3 The Transition Tool There are four arc tools for those different arc types that are generally available Arc Tool This tool is used for creating input and output arcs which only have one arrow tip at their ending If the start figure of the connection is a place and thus the end figure has to be a transition this one way arc is an input arc If the start figure is a transition we have an output arc Test Arc Tool Here test arcs without any arrow tips are created A test arc has no direction as no tokens are actually moved when the transition fires see Section 3 12 1 This means it does not matter whether you start a test arc at the place or at the transition Re
191. ow accepts the selection of multiple files This will result in 2 0 multiple drawing windows to be opened in the editor simultaneously Dependent on the set of installed plug ins and on your window manager one of several available drawing file types can be chosen from a drop down box in the dialog This will restrict the display of files in the dialog You may override the file type filter by specifying a wildcard pattern like as file name and pressing Enter Insert Drawing This function opens a previously saved drawing to be inserted into the currently focused drawing editor Opening works like in Open Drawing All figures which are selected before insertion are deselected In return all the inserted figures are selected now which makes it easy to move them around without jamming the other figures Save Drawing This function saves the active drawing see Section 4 2 to a file using a textual format The drawing is saved to the last file name used which is the file it was loaded from or the file it was last saved to If the drawing has not been saved before this function behaves like Save Drawing As see below If there is an old version of the file it is overwritten Depending on your operating system overwriting a file might need confirmation by the user you The keyboard shortcut for this function is Ctr1 S Save Drawing As This functions is used to determine a new file name for a drawing and save it in te
192. pened the same net twice Maybe you have created new nets which have the name untitled by default and you have not saved the nets yet Flexible arcs must be inscribed A flexible arc is not equipped with an inscription Flexible arcs are supposed to move a variable amount of tokens to or from a place but this arc does not depend on any variables and lacks the required variability Maybe you did not yet specify an inscription Maybe the inscription is attached to the wrong net element Maybe you want to use an ordinary arc instead For non array inscriptions the place must be untyped An inscription of a flexible arc is given as a list or a vector or an enumeration but the output place is typed The resulting restriction on the element types could not be verified Maybe it is possible to use an array inscription Maybe the place should not be typed Incorrect type for flexible arc inscription An inscription of a flexible arc is expected to evaluate to an array or a list or a vector It is only allowed to use enumerations on output arcs because the elements might have to be accessed multiple times in the case of input arcs Use an inscriptions that is correctly typed Maybe the compiler determined the type java lang Object but it is known that only arrays will result from the expression In that case use an explicit cast to indicate this fact Null not allowed for flexible arcs An inscription of a flexible arc is expected to evaluate to
193. ports automatic inscription generation Click on a net element figure with the right mouse button and a new inscription figure is created with a default inscription depending on the type of net element This is especially convenient for arc inscriptions since these usually consist of a single variable Of course in most cases you have to change the inscription afterward but you do not need to use the inscription tool Instead you right click on the net element and then right click on the newly created inscription The Transition Tool This tool functions almost exactly like the rectangle tool The differences are e Only transition figures have a semantic meaning to the simulator A rectangle figure is ignored by the net execution engine 75 e To create a transition with a default size after selecting the transition tool just click instead of drag The position of the click specifies the center of the newly created transition e A transition figure offers an additional handle The arc handle a small blue circle in the middle of the figure can be used to create new output arcs see Section 1 3 3 The Arc Tool The new handle has a special behavior when you stop dragging on figure that is not ap propriate as a target for the arc A normal connection is deleted when there is no appropriate end figure However for an arc it is quite clear what kind of figure is supposed to be there a place figure And this is what happens Automati
194. provided in Java Here we are going to discuss those operators that are still present in reference nets The binary operators are listed in Table where we also note their interpretation and the operand types to which each operator is applicable Most of the operators are defined for primitive types only but you can also check if two references are identical with and the Java method equals asin s1 equals s2 or you will get strange results This is a peculiarity that annoys many Java beginners but we are not in a position to change this behavior ry Never use or to compare the equality of strings like in si s2 Always use The operator is also used to concatenate strings If only one operand of is a string the other operand is first converted to a string and the two strings are concatenated afterward e g 7x8 42 results in the string 7x8 42 If multiple operators are present they are grouped according to their precedence and have the highest precedence has the lowest precedence The expression a b cx d e is equivalent to the fully parenthesized expression a b c x d le The order of precedence for each operator can be found in Tab 3 2 If in doubt make the parentheses explicit An operand of a small type byte short or char is automatically converted to int before any operator is applied If you need the result as a small type you have to make an 40 multiply number divide number
195. ps Middles Bottoms These commands work exactly like the commands in the pre vious paragraph except that the y coordinate is changed Thus figures are moved vertically in order to be aligned with their tops middles or bottoms The keyboard shortcut for aligning middles is Ctr1 the minus sign Spread The items of this menu spread the selected figures equidistantly The two outermost figures that are selected stay at their previous location while all other selected figures are reposi tioned The order of the figures left to right top to bottom or diagonal remains unchanged To use the spread commands you must have selected at least three figures Lefts Centers Rights Distances Here we spread the figures by modifying their x coordinates The y coordinate remains unchanged Lefts arranges the figures in a way that the x coordinates of their left borders are distributed equally Rights does the same with respect to the figure s right borders Centers with respect to each figure s center point Distances arranges the figures in a way that the space in between of each pair of neighboring figures will have the same width The differences between the four commands will only be visible when figures of different sizes are selected Tops Middles Bottoms Distances These functions work exactly like the functions in the previous paragraph except that the y coordinate is changed Thus the figures are moved vertically to equal the distances
196. rc extensions for coloured petri nets In R Valette editor Application and Theory of Petri Nets 1994 Proceedings 15th International Conference Zaragoza Spain volume 815 of Lecture Notes in Computer Science pages 338 357 Springer Verlag 1994 Available at http www daimi au dk sorenchr publ html Peter Langner Christoph Schneider and Joachim Wehler Petri net based certification of event driven process chains In J Desel and M Silva editors Application and Theory of Petri Nets 1998 Proceedings of 19th International Conference Lisbon Portugal volume 1420 of Lecture Notes in Computer Science pages 286 305 Springer Verlag 1998 Carl Adam Petri Introduction to general net theory In Brauer W editor Net Theory and Applications Proc of the Advanced Course on General Net Theory of Processes and Systems Hamburg 1979 volume 84 of Lecture Notes in Computer Science pages 1 19 Springer Verlag 1980 Wolfgang Reisig Petri nets and algebraic specifications Theoretical Computer Science 80 1 2 1 34 1991 Wolfgang Reisig Elements of Distributed Algorithms Modelling and Analysis with Petri Nets Springer Verlag 1998 R diger Valk Petri nets as token objects An introduction to elementary object nets In J rg Desel and Manuel Silva editors Application and Theory of Petri Nets volume 1420 of Lecture Notes in Computer Science pages 1 25 Springer Verlag 1998 Peter van der Linden Just Java The Sunsoft Press J
197. re about their theoretical foundations do not use them No compromises where made in the simulation engine to allow their implementation so that robustness of Renew is not affected 3 10 1 Flexible Arcs Flexible input arcs and flexible output arcs were introduced by Reisig in 16 They allow multiple tokens to be moved by a single arc Moreover the token values and even the number of tokens may vary with the binding of the transition s variables In Renew these arcs are indicated by attaching two arrowheads instead of one to the end of the arc In the original article no such distinction was made but instead the flexible arcs were indicated by the type of the arc inscription which is not feasible in the case of reference nets Besides flexible arcs do not occur that often and they do deserve some special attention and highlighting The inscriptions of flexible arcs must be of an array type All elements of the array that is calculated from the arc inscription are successively removed from the input place or put into the output place depending on the direction of the arc If one Java value occurs multiple time in the array an equivalent number of corresponding tokens will be removed The order of the values in the array does not matter Arrays are preferred over vectors or other container objects because they allow the use of primitive values whereas vectors can only carry references to objects This can cause some inconveniences to the d
198. ripts have a similar behavior when it comes to the interpretation of environment variables while their specific effects are explained in other Sections of this manual script name use renew starts the Renew editor loadrenew Java drawing load client see Subsection 2 6 2 for details makestub generates a net stub from a Java interface compilestub compiles a net stub to Java code jcompile wrapper for javac that includes some Renew classes in the CLASSPATH see Subsection 3 9 1 for details Table 2 1 The startup and stub scripts 2 5 1 Mac OS X From version 2 4 3 onward Renew requires at least Java 1 7 14 Since Mac OS X is built upon a Unix core you can follow the installation directions for Unix To do so open the Terminal application which can be found in Applications Utilities Renew With the maintenance release 2 0 1 we provide an experimental AppleUI plug in 2 0 1 as optional download This plug in adds rudimentary support for native MacOS look amp feel to Renew It allows the cmd q or apple q shortcut to close the editor properly with safety questions for unsaved changes and it slightly modifies the MacOS menu bar See Section 2 7 1 on how to install the plug in Renew With the maintenance release 2 1 1 we provide an experimental Mac OS X appli 2 1 cation bundle for download which can replace the Unix style installation of Renew The application is configured in GUI only mode without console output or
199. ry with wget http www informatik uni hamburg de TGI renew renew gpg add the key to the trusted keys and install Renew by running the following commands as superuser apt key add renew gpg apt get update apt get install renew 15 2 5 3 Windows For Windows we provide an installation script in the directory renew2 4 3 bin win for your convenience This batch file has to be started from its own directory cd renew2 4 3 bin win installrenew This will create the batch files renew bat loadrenew bat makestub bat compilestub bat and jcompile bat in the same directory see Table P I Renew Additionally the files addregistry reg and removeregistry reg will be created 2 4 addregistry reg contains the registry entries to associate Renew file types rnw draw aip sns with the loadrenew bat script You can perform this asso ciation by double clicking addregistry reg With removeregistry reg you can remove the corresponding entries from the registry Admin rights are required to edit registry entries The update of the icons for the Renew file types may need a restart to take effect However you must make sure that java can be called with your current setting of the PATH environment variable It is also required that you start the installation script from the bin win directory otherwise it cannot find the location of the package Please check your classpath variable for any unquoted whitespace in it because batch scripts
200. s formalism is not any longer distributed with the base renew distribution this mode is not available unless you install the fs plug in In Expanded Tokens mode token objects are shown in a UML like Unified Modeling Language notation An object is noted by a box containing two so called compartments import java awt O Menu label File tems label Load label Save Figure 4 4 An Example of Browsing Token Objects in Expanded Tokens Mode The first compartment specifies a temporary name of the object Renew just gives numbers to objects followed by a colon followed by this object s class name According to UML the whole string is underlined to indicate that this is an instance not the class The second compartment is only shown if you click the shutter handle a small yellow rectangle with a cross plus sign inside Otherwise the available information is indicated by three dots after the class name The second compartment contains a list of all attributes of the token object and their values which are basic types or again objects Multi valued attributes e g array values or Enumerations are shown as lists in sharp brackets this part is not quite UML After opening the attributes compartment the handle changes to a horizontal line minus sign and lets you close the compartment again if you wish to do so This way you can browse the object graph starting at the token object If the
201. s the control key is pressed The behavior of white square point handles can be modified with the control key similar that of location handles of connections see above It can now be configured how the polygon smoothness lines by removing intermediate points The property ch ifa draw polygon smoothing can be set to the following values changes take effect the next time a polygon is manipulated alignment This is the default behavior as it was implemented in previous Renew releases Points are removed if they are located on a straight line between their adjacent points distances Points are removed only if they are too close to each other less than 5 pixels distance horizontally and vertically off No smoothing at all no points are removed The Image Tool The image tool offers you the possibility to include bitmap graphics into your drawings When activating this tool a file dialog box opens that lets you choose a bitmap graphic file from your file system gif files should work on all platforms but other formats like jpg too Java and thus Renew even supports transparent GIF images y Be aware that the PostScript output does not yet support transparent GIF images 4 but some of the other export formats e g PDF and SVG do After you confirmed the file selection the dialog disappears and leaves you with two options Either you just click somewhere in your drawing or you drag open an area just like when creating a rectangle
202. s to snap figures to a grid to align a figure s position according to other figures to change the Z order of figures and to layout graphs automatically 86 Toggle Snap to Grid Selecting this menu toggles the Snap to Grid mode of Renew This grid is not absolute referring to the page but means that when the grid is active figures can only be placed to grid positions and moved by certain offsets Because the editor considers offsets while moving not absolute coordinates figures should be aligned first see below and then moved in grid mode The grid function is also very basic because the grid density is not customizable Align The commands in this menu align the selected figures The figure selected first is the reference figure which determines the coordinates for all others Lefts Centers Rights These commands align the figure s x coordinates i e they move them horizontally Lefts sets the left hand side of all selected figures to the x coordinate of the left side of the figure that was selected first Rights does the same for the right hand side Centers takes into account the width of each figure and places all figures so that their x center is below the reference figure s x center The keyboard shortcut for aligning middles is Ctr1 the backslash character j The shortcut works only on an English keyboard layout where the keys for the A shortcut can be typed directly i e without additional modifiers like Shift To
203. select children select children select associated place select children select select parent open binding window select marking select place instance select place instance right click select drag text edit text edit attach inscription s O attach inscription attach inscription attach edit inscription text edit text edit fire arbitrary binding open current marking window show token marking show cardinality marking Table 4 1 Summary of selection tool operations for documentation or illustration purposes You may lack some functions that you are used to from your favorite drawing tool like adjusting line width and such but remember that Renew is a Petri net tool not a drawing tool in the first place The Rectangle Tool The rectangle tool is used for creating new rectangle figures Press the mouse button at the point where the first corner is supposed to be and drag the mouse to specify the opposite corner while holding down the mouse button While dragging you can already see the rectangle s dimension and location which is confirmed as soon as you release the mouse button After a new figure has been created the new figure is not automatically selected To do so just click on the figure with the selection tool see Section 4 3 1 Now the figure s handles appear In the case of a rectangle or ellipse figure these are sizing handles which are displayed as small white boxes at the corners of the
204. serve Arc Tool With this tool reserve arcs with arrow tips at both sides are cre ated Again the direction does not matter For the semantics of reserve arcs see Section 3 12 1 Flexible Arc Tool An arc with two arrow tips on one side is created These flexible arcs transport a variable number of tokens For the semantics of flexible arcs see Section There are two additional arc tools that are only displayed on request as described in Subsection 4 4 6 Clear Arc Tool This tool is used for creating clear arcs which remove all tokens from a place You have to select the place as the start figure and the transition as the end figure during the creation of a clear arc For the semantics of clear arcs see Section 3 10 2 Inhibitor Arc Tool This tool is used for creating inhibitor arcs which stop the attached transition from firing as long as certain tokens are contained in a place This arc features circles at both of it end points Again the direction does not matter For the semantics of inhibitor arcs see Section 3 10 3 Using the Attributes menu it is possible to change the direction of an arc after its creation Simply select the desired value for the attribute Arrow However you cannot currently change ordinary arcs to flexible arcs or vice versa Neither can you access inhibitor or clear arcs this way Let us repeat from Section 4 3 2 that you can create intermediate points by selecting an arc tool before
205. sformations to either scaling or rotation Keyboard movement of figures with arrow keys can now be sped up using the Shift modifier The behavior of Search and Replace has been fixed so that multiple instances of the search string in the same figure are now found and replaced correctly The Drawing Load Server has been restricted to accept local connection requests only Additions Renew now includes and uses the VectorGraphics packages of the FreeHEP project to ac complish graphical export of drawings Additional supported export formats are PDF SVG and PNG EPS export now exports non standard fonts correctly at the price of larger files EPS files now always have a rectangular white canvas A new pie figure allows to draw segments of arcs and ellipses Line styles dotted dashed etc can now be applied to boxes ellipses and other figures with outlines A transparency attribute has been added to all figure font and pen colors This breaks compatibility with older Renew versions so that drawings saved with version 2 2 can not be opened by pre vious versions except release 2 1 1 The transparency attribute is currently ignored when exporting drawings to EPS and this feature might not be implemented in future versions For drawings with transparency use one of the two new export formats SVG or PDF which handle transparency correctly The hotkey Ctrl M now brings the menu and toolbar frame to front Added show net pattern instance elem
206. side ER under the Tools menu Since version 2 3 it is also possible to determine the position of the menu item within the menu The Navigator plugin extends the File menu Ctrl Shift N 4 5 Net Simulations Renew During simulation there may be textual and graphical feed back The Log4j frame 2 1 work receives simulation events and can log them alternatively to the console a file the trace window etc In Subsection 4 4 6 the graphical configuration dialog for Log4j is explained In a trace of log events you can see exactly which transitions fired and which tokens were consumed and produced But you can also view the state of the various net instances graphically and you can influence the simulation run 4 5 1 Net Instance Windows The graphical feed back consists of special windows which contain instances of your reference nets When a simulation run is started the first instance of the main reference net that is generated is displayed in such a net instance window As in the simulation log the name of a net instance and thus of its window is composed of the net s name together with a numbering in square brackets e g myNet 1 Net instance windows can also be recognized by their special background color something bluish purple so they cannot be confused with the windows where the nets are edited In a net instance window you cannot edit the net you cannot even select net elements The net is in a background layer a
207. sion of the Mac OS X application bundle It fixes issues concerning the export functionality with newer Java versions This version requires at least Java 7 36 Chapter 3 Reference Nets First we are going to take a look at Petri nets with Java as an inscription language Then we look at synchronous channels and net references two extensions that greatly add to the expressiveness of Petri nets as described in 9 and TO Finally we are going to see how nets and Java can seamlessly interact with each other Reference nets and their theoretical foundation as a whole are defined in II in German 3 1 Net Elements Reference nets consist of places transitions and arcs There are many types of arcs Firstly ordinary input or output arcs that come with a single arrow head These behave just like in ordinary Petri nets removing or depositing tokens at a place Secondly there are reserve arcs which are simply a shorthand notation for one input and one output arc Effectively these arcs reserve a token during the firing of a transition Thirdly there are test arcs which have no arrowheads at all A single token may be accessed i e tested by several test arcs at once This is important because an extended period of time might be needed before a transition can complete its firing For a more detailed treatment of test arcs see 6 Besides these basic arc types there are arc types that add greatly to the expressiveness of nets but
208. sion of Renew you should simply skim the manual and look for the Renew 2 4 icons as shown to the left The paragraphs that are tagged with this icon elaborate on new features of the current version You should also consult Section for some notes on the upgrade process The upgrade might require some explicit actions on your part Advanced users may want to consult the architecture guide doc architecture ps in the source package of Renew if it is intended to modify Renew It is not recommended for the casual user to spend much time reading this manual as it is quite technical and of little help in the day to day use of Renew 1 3 Acknowledgements We would like to thank Prof Dr R diger Valk and Dr Daniel Moldt from the University of Hamburg for interesting discussions help and encouraging comments We would also like to thank Sofiane Bendoukha Jan Bolte Lars Brauer Michael Hauster mann David Mosteller Julian Mosteller Felix Ortmann Dennis Reher Fabian Sobanski and Thomas Wagner for their work during the preparation of this release We would like to thank J rn Schumacher for the prototype of the plugin system 2 0 Benjamin Schleinzer for his work during the preparation of former releases 2 1 2 2 and Berndt Miller who has been of great help with respect to previous Renew releases for Mac OS lt 2 0 Some nice extensions of Renew were suggested or programmed by Michael K hler and Heiko Rolke We are indebted to the authors of v
209. starts a new instance of the whole application This is extremely nasty when using a Java application since a new Java Virtual Machine is started every time To avoid this problem with Renew we added a simple server function to Renew By setting the property de renew loadServerPort to a port number you can tell Renew to listen for requests to load a certain drawing on a TCP IP socket Just specify an unused TCP IP port number say 65111 either on the command line or in the configuration file see Section 2 6 1 When Renew is started with this property the Drawing Load Server is set up on the given port and waits for clients to connect and transmit the full filename of a drawing to open followed by an end of line Changing this property s value at runtime has 17 no effect The port 65111 is used by default If you do not want to start a Drawing Load Server you can set the property to 1 Renew As a security measure the Drawing Load Server is now restricted to local loopback 2 2 connections It will not any longer accept connections from other hosts in the network However on multi user machines other local users are still able to connect We provide a generic client application written in Java that can be used as a Drawing Load Client In the meantime Java Virtual Machines and computers have become much faster but it is still questionable whether it is a good idea to start a JVM each time you want to load a drawing
210. t expressions are not evaluated backward The only exception are type casts which we met earlier on A type cast that may be performed without losing information e g long i for an integer i can be calculated backward If due to an equality specification the result of such a cast is known it is propagated backward to the casted expression possibly 44 action b new Button import java awt 0 Jaba daba doo action f add b Button b 8 ny 8 A Frame f b b f f f f action f show AA 4 action f dispose f ll action f new Frame action f setSize 500 500 Figure 3 7 The net frame after some conversion If a backward computation is desired in the other cases it has to be made explicit In our example we could complement the equation z x y by x z y and y z x Now the simulator can determine y from x and z This is allowed exactly because does not mean an assignment but an equality specification If a bound variable is calculated again by a redundant equation this does not pose a problem as long as the two bindings are equal If does not assign what do the modifying operators and so on mean in reference nets Simple answer They make no sense and were therefore excluded from the language Similarly the operators and do not appear 3 4 4 Method Invocations Reference nets also support method invocations E g x meth a invokes the method meth of the object referenced by x with the par
211. t of the declaration figure is used for import statements as well as variable declarations see Section B 4 2 As in the case of inscriptions see above the content of a declaration figure is syntax checked as soon as you stop editing For an explanation of syntax errors that may occur refer to Section 4 7 4 4 Menu commands This section contains a reference to Renew s menus and the functions invoked by them 4 4 1 File As usual the file menu contains every function that is needed to load save and export drawings In the following section all menu items of the file menu are explained New Net Drawing rnw This menu invokes a function that creates a new drawing and opens it in a drawing window in a default window size The new drawing is named untitled and is added to the list of drawings in memory see Section 4 4 7 The keyboard shortcut for this function is Ctr1 N 78 a New Drawing Renew Since Renew now supports different kinds of drawings dependent on the installed 2 plug ins this menu entry opens a dialog where the type of drawing can be chosen Select the appropriate drawing type in the dialog and press the New button Open Navigator Renew This command opens the Renew file navigator in a new window The navigator 2 3 displays folders and their Renew related content in a directory tree The navigator Pue is shown in 3 The keyboard shortcut for this function is Ctr1 Shift N Renew PNML
212. t visible it cannot be selected by the mouse any more but the select commands from the menus Edit or Net will still include the figure when appropriate This feature is useful especially in combination with the Associate highlight command from the net menu The invisible figure will appear in the instance drawing while it is highlighted Arrow This attribute is only valid for the connection and the arc figure and offers four possibilities of arrow tip appearance None at Start at End or at Both ends of the line If the figure is an arc its semantics are changed accordingly Arrow shape This attribute is valid only for lines or connection figures The style of arrow tips can be changed to one of four shapes which are usually used to mark different semantics of arcs in Renew But as it is currently not possible to change the arc semantics in accordance to the arrow tip shape this attribute will not have any effect on arc figures Line Style Every line possesses a line style which can be chosen out of the options normal dotted dashed medium dashed long dashed or dash dotted Lines are typically created as solid normal lines It is also possible to define your own line style After choosing the option other you can enter any custom line style in a non modal dialog The dialog has four buttons Apply Update OK and Cancel that work similar as in the Fill color dialog see above A custom line style consists of a space separated
213. ted useful analysis seems a long way off Cur rently Renew relies entirely on simulation to explore the properties of a net where you can dynamically and interactively explore the state of the simulation However for many applications analysis does not play a prominent role Petri nets are often used only because of their intuitive graphical representation their expressiveness and their precise semantics During simulation the user cannot change the current marking of the simulated net except by firing a transition This can make it somewhat more difficult to set up a desired test case In our formalism there is no notion of firing probabilities or priorities By exploiting the open architecture of Renew these features may be added later on possibly as third party contributions Renew is an academic tool Support will be given as time permits but you must be aware that it might take some time for us to process bug reports and even more time to process feature requests But since Renew is provided with source code you can do many changes on your own And your feature requests have a high probability to be satisfied if you can already provide an implementation How to Read This Manual It is generally recommended to read all chapters in the order in which they are presented However when somebody else has installed Renew for you you should skip Chapter B entirely Renew 2 4 If you are already familiar with a previous ver
214. th each other Here we have true concurrency in the simulation because the method is invoked in the background in a separate thread and operates independently of further firings In fact actions that include a method call are always executed in the background But often the search for a new binding takes so much time that the background thread finishes long before the next binding is found But here we have a method that requires a synchronous communication before it com pletes Such methods rely on the simulator thread to find a matching channel and they require more than one step in any case Renew The stub compiler now recognizes the declaration class Name for netinstance 2 2 without a specific net name as an alternative to the declaration given above Such a stub class owns a one argument constructor that expects an existing net instance to be wrapped by the stub object The stub object can be passed around like any plain Java object It forwards its method calls to synchronous channels of the wrapped net instance as explained above It should be noted however that there are two objects with individual identities involved the stub and the net instance In contrast the for net netname decla ration creates one single object only which is both the stub and the net instance 3 9 2 Event Listeners Nets that implement methods might be useful for designing a graphical user interface where the window system sends events that must be processed
215. that long is a subtype of float although some loss of preci sion might occur during the conversion Nevertheless Java will silently insert this conversion whenever it is required in a program Although this is helpful for Java programs it poses several problems in the context of Petri nets where the direction of information transfer is not always immediately obvious Hence such conversions are not done by the simulator Instead we introduced the relation of lossless conversions which you can find on the right hand side of Figure 3 3 This relation governs the type constraints between places and their neighboring arcs All other types except primitive types are reference types i e references to some object Every object belongs to a class When a class is declared it may receive an arbitrary number of field declarations and method declarations Fields are variables that exist once per object or once per class The binding of the fields of an object captures the state of that object Methods describe the possible actions of an object Each method has a name a list of parameters and a body i e a sequence of statements that are executed if the method is invoked Method declarations and field declarations are nested in the declaration of the class to which they belong It is possible to use the predefined classes without writing new ones when working with Renew We are going to see later how nets themselves can be regarded 39 double long dou
216. the default configuration informational and error messages are printed to the console and logged to a file The simulation trace also goes to the logging framework see Section 2 6 10 The new Logging plug in provides a simulation trace window within the GUI The Net step option has been added to the simulation menu 2 9 12 Changes in Version 2 1 1 Modifications This was a maintenance release that provides several minor bug fixes for PNML export null token display and access to public methods of private inner classes in Java expressions In addition this release is capable of reading drawing files created with the later release 2 2 with some minor exceptions Additions The AppleUI plugin now supports building a MacOS X application bundle 2 9 13 Changes in Version 2 2 Modifications Java 1 5 is now required for compiling and running Renew The Gui now uses the Graphics2D Framework that came with Java 1 2 so some of the figures might be drawn a little bit different when it comes to size and style Tokens are now displayed on a white opaque background in the token game to increase readability Scrolling now continues if the mouse is moved outside a drawing while a button is pressed Modifier keys Ctrl Shift have been added to several commands and tools on drawing figures These enable users to resize figures to equal width and height to adjust polygon vertices at right angles with their adjacent edges and to restrict polygon tran
217. the simulation is performed step by step see below Interactive simulation is possible You can force a specific enabled transition to fire in two ways e Right click the transition Here the simulation engine still decides nondeterministically about the variable bindings e Double click the transition Then the so called binding selection window is shown and switched to the transition you double clicked The title of the window says transition name s possible bindings where transition name is the full name name of the net instance dot transition name of the transition In the top part of the window a single binding is described Each transition instance that participates in this binding is shown on a single line listing those variables that 105 are already bound See Section 3 7 for an explanation why multiple transition instances might participate in a single firing At the bottom of the window there is a list of all possible bindings where each binding is displayed in a single row When you press the Fire button the binding of the entry which is currently selected will be used in the firing This window should be automatically updated whenever the net s marking changes Use the Update button if the automatic update fails and make sure to report this as a bug Close hides the transition binding window If the clicked transition is not activated the status line of the Renew window tells you so and nothing else is go
218. ther entry at the end of the list opens a dialog where you can enter any number as size The dialog has four buttons Apply Update OK and Cancel that work similar as in the Fill color dialog see above Font Style Available font styles again only for text based figures are Italic and Bold If you select a style it is toggled in the selected text figure s i e added or removed Thus you can even combine italic and bold style To reset the text style to normal select Plain Text alignment The direction of text justification can be configured by this attribute This will affect the alignment of lines in text figures with multiple lines as well as the direction of growth or shrinking when a text changes its width due to a change in its text length By default inscriptions and other connected text is centered at the parent figure while other text figures are left aligned Text Color The text color attribute is only applicable to text based figures and sets the color of the text sic This is independent of the pen and fill color The default text color is of course black The other entry at the end of the list of colors opens a full featured color chooser dialog as described under Fill color Text Type This attribute is quite nice to debug your reference nets quickly The text type determines if and what semantic meaning a text figure has for the simulator If a text figure is a Label it has no semantic meaning at all If
219. ther textfields overlap by more than 50 Overlap indicates problems in the clear representation Also the situation is detected that a second inscription is accidentally assigned to an arc and is hidden because of the overlap 4 4 6 Simulation This menu controls the execution or simulation of the net system you created or loaded Before a simulation can be started all necessary nets must be loaded into memory see subsection 4 4 7 The drawing window containing the net that is to be instantiated initially has to be activated Refer to Section 4 5 if you want to learn how to monitor and influence a simulation run that you have started using this menu Run Simulation This function starts or continues a simulation run that continues automatically until you stop the simulation If you want to enforce starting a new simulation run use Terminate Simulation see below first For most net models it is almost impossible to follow what s going on in this simulation mode Its main application is to execute a net system of which you know that it works Some syntax checking is done even while you edit the net see Section 4 3 3 The Inscrip tion Tool but when you try to run a simulation of your reference nets the reference net compiler is invoked and may report further errors see Section 4 7 You have to correct all compiler errors before you can start a simulation run The keyboard shortcut for this function is Ctr1 R 97 Simulation
220. tion has an uplink that is not invoked by another transition Generally transitions with an uplink cannot fire without being requested explicitly by another transition with a matching downlink We will sometimes call a transition without an uplink a spontaneous transition But even a spontaneous transition must find an appropriate synchronization partner if it has a downlink It is allowed that a transition has multiple downlinks It is also allowed that a transition has both an uplink and downlinks This is exemplified in Fig Again the transition on the left initiates the synchronization The required channel is offered by the middle transition which does nothing except linking to the channel bar twice This is allowed a transition may fire multiple times in one synchronous step although it might be confusing and should be avoided when possible In general multiple levels of synchronization are suspect from a methodical point of view because they tend to be difficult to understand Petri nets excel at displaying control flow and it seems that synchronous channels should not be used to encapsulate complex control flows or even loops It is best to use channels where they show their greatest potential namely synchronization communication and atomic modifications Channels can also take a list of parameters Although there is a direction of invocation this direction need not coincide with the direction of information transfer Indeed it is possib
221. tor is It cannot be an assignment because variables are immutable Instead it is merely a specification of equality You will usually want equality specifications to occur inside special inscriptions that are attached to transitions E g you can say x 2 to bind the variable x to 2 or you could use x y z 42 for a more interesting computation If you specify both x 2 and x 3 for a single transition that transition will not be able to fire because x cannot be bound in a way that matches both specifications Keep in mind that is based on equality in the sense of the equals Object method and not in the sense of the operator This might confuse experienced Java programmers but it is the only possibility to avoid certain other anomalies In the net from Fig 3 6 you can see two transitions that perform equivalent actions as you can see when you load the nets from samples simple and simulate them The transition on the right uses a variable z to hold the value of the computation x y At the left we see an example where an expression occurs on an input arc Such expressions are properly evaluated and the simulator checks whether the resulting token is available But expressions on input arcs have to be used with care Just because the simulator knows that x y equals 24 and x equals 22 it cannot conclude that y is 2 Such computations would have been possible in some cases but not in others Due to consistency we decided on the general rule tha
222. trivial functionless classes By the way this is what has to be done in Java in some cases too Tuples are weakly typed They are of type de renew unify Tuple but their components are untyped It is not even specified whether a component of a tuple holds a primitive or a reference type This does not matter much because the only operation on tuples or rather the only operation that should be used is unification You can unify tuples through an equality specification E g x y z t means that t must be a 3 tuple Furthermore x will be equal to the first component of t y to the second and z to the third We already know that the black token is denoted by Therefore a black token is simply a tuple without components a zero tuple In Fig 8 8 we can see the sock algorithm of the typical theoretical computer scientist The scientist will reach into the drawer to fetch two socks It does not matter if the socks are left socks or right socks they are topologically equivalent as long as they are of the same color In the net which can be found in the directory samples tuple this is achieved by using the variable col in both arc inscriptions that will remove tokens from the drawer place Tuples may be nested 1 2 3 4 5 would be a 2 tuple that has a 2 tuple as its first component and a 3 tuple as its second component This might be useful if the components are hierarchically structured It is a common task to use tuples to simulat
223. ty of the net decreases because of many crossing arcs With a virtual place copy you can draw the same place many times thus avoiding such crossing arcs and arcs over long distances You create a virtual copy of a place by activating the virtual place tool then clicking on the place you want to copy this can also be a virtual place and keeping the mouse button down while dragging the virtual place figure to its destination location The virtual place can be distinguished from a normal place by the double border line see the graphics inside the tool button To find out which place a virtual place belongs to just double click the virtual place To make this relation visible in printed versions of your nets you should copy the name of the place to the virtual place Unfortunately the tool does not take care of the names of virtual places automatically Another solution supported by the tool is to give each group of a place and all its virtual copies a different fill or pen color All places belonging together will change their colors if you change the color for one place During simulation every virtual copy of a place contains exactly the same token multiset as its original place Still it is possible to determine the marking appearance separately for each virtual place and the place itself see Section 4 4 6 A A nice way to take advantage of this feature is to create virtual copies of places Y with an important and extensive marking and m
224. ue We will indicate such methods with the keywords break void suggesting that another thread of control breaks off the main thread As an example we will create nets that display a window with three buttons that grow shrink and close it A similar exercise is given in 19 The interface ActionListener is implemented by package samples call class SizeChanger for net sizechanger implements java awt event ActionListener SizeChanger java awt Frame frame this setFrame frame break void actionPerformed java awt event ActionEvent event this putEvent event The constructor takes one argument namely the frame whose size should be changed The single method is designated break void so that it can return before any synchronizations are performed This stub is contained in the file SizeChanger stub that resides in samples call along with the nets from Figs 8 20 and B 21 The net buttonmaker is used to construct the frame with its buttons and the SizeChanger object Later on each mouse click on one of the three buttons results in an event that is 55 P action frame setSize 400 400 A frame setFrame frame E Y frame Y L frame Ea X action frame setSize 200 200 event getActionCommana j Ka X small frame close A action frame dispose Figure 3 21 The net sizechanger propagated to the sizechanger net Every event is equipped with a command string that
225. use the layout algorithm may become unstable for very low friction values and convergence to an equilibrium might actually slow down due to oscillations The optimal value depends heavily on the topology of the net If you feel that you cannot set some force s strength high enough consider lowering the other forces and also lowering the friction a little A Even while the graph is changed automatically you can still grab a node with Y the selection tool and move it to a desired position Of course it might fall back into the old position due to the acting forces but your action might establish a topologically different situation where the forces act toward a different equilibrium This is especially useful when you have selected high torque and rigid springs but low or no repulsion After you are satisfied with the graph switch off the layout mode If you add or remove nodes or arcs during the layout procedure you have to restart the net layout algorithm before these changes affect the layout algorithm Note that the start of a layout procedure always affects the current drawing not the drawing that was previously used for layout Location Using this menu you can declare the currently selected figures as either fixed or dynamic Dynamic nodes participate in the automatic layout as usual which is the default On the other hand fixed nodes still exert forces upon other nodes but they are rigidly glued to their position and move only if
226. ution includes four formalisms represented by their compilers P T Net Compiler compiles the net as a simple place transition net It accepts integer numbers as initial markings and arc weights Capacities are not supported Java Net Compiler encapsulates the reference net formalism with Java inscriptions as de scribed in chapter 8 However this compiler does not accept time annotations Timed Java Compiler represents the same formalism as the Java Net Compiler but with additional time annotations as explained in section Nets compiled by this compiler must be executed in a sequential simulation Bool Net Compiler compiles nets according to the formalism presented in 14 A bool net is a restricted colored net with exactly one color bool 0 1 can also be represented as false true It accepts one of the propositional logic operators and or and xor as transition guard inscriptions Show sequential only arcs Renew This option is available only when the Java Net Compiler is chosen as current 2 0 formalism Selecting this option adds another toolbar to the editor This toolbar comprises two additional arc types see section 1 3 3 which are allowed in sequential simulations only Please note that this option is automatically enabled although the menu entry is not visible when you choose the Timed Java Compiler as formalism 103 For your convenience the sequential simulation mode see sections 1 4 6 and 2 6 5 is activated ea
227. variable could not be found in the declarations Maybe the name was misspelled Maybe a declaration is missing Not an array Only expressions of an array type can be postfixed with an indexing argument in square brackets Numeric type expected A boolean expression was used in a context where only numeric expressions are allowed possibly after a unary numeric operator Operator types do not match No appropriate version of the operator could be found that matches both the left and the right hand expression type although both expression would be valid individually Primitive type expected Most operators can act only on values of primitive type but the compiler detected an object type Type mismatch in assignment An equality specification could not be implemented because the types of both sides are incompatible One type must be subtype of the other type or the types must be identical Variable must be assignable from de renew net NetInstance The variable to which a new net is assigned must be of type NetInstance i e of exactly that type of type java lang Object or untyped E g it is an error if in x new net the variable x is of type java lang String Maybe you have to use an intermediate variable of the proper type and perform a cast later Variable name expected The identifier to which a new net is assigned must denote a variable E g it is an error if in x new net the identifier x is a class name Cannot clear untyped place using type
228. ving seen the handle itself If you want to get rid of a pin point simply select the connection and double click the associated handle Another more complicated way to remove intermediate points is to select the connection tool and click on the intermediate point with the left mouse button A If you move two figures a straight connection is automatically moved with them b But if the connection has intermediate points these stay at their old location Solution Just select the connection itself additionally and everything will move Y together The Elbow Connection Tool The elbow connection tool establishes a connection between two figures just like the con nection tool The difference is that an elbow connection does not draw a direct line from one figure to the other but uses straight horizontal or vertical lines only When you select an elbow connection you see up to three yellow handles which adjust the position of the horizontal and vertical lines Changes to these handles are not stored Also if the connected figures are close 4 together the decision whether to go horizontal or vertical first is quite poor Since no elbow connections are needed to construct reference nets we do not really care about these bugs The Scribble Tool The scribble tool lets you scribble in a drawing with your mouse just like the famous Java applet More precisely a scribble figure traces the mouse movement while the button is held down
229. vious example action x o m would have to be executed first because it is required to determine the binding for x In the same sense the action keyword only applies to a single expression not to all following expressions E g action y o m x x o m would mean that x o m is evaluated early during the search for a binding because it is not an action 45 l right red left green left drawer col type1 col type1 blue right red left col type2 col type2 take socks green right left Figure 3 8 The net socks 3 5 Tuples Lists and Unification The inscription language of reference nets has been extended to include tuples A tuple is denoted by a comma separated list of expressions that is enclosed in square brackets E g 1 abc 1 0 denotes a 3 tuple which has as its components the integer 1 the string abc and the double precision float 1 0 Tuples are useful for storing a whole group of related values inside a single token and hence in a single place In ordinary Java there are no tuples If we want to store a group of values we can simply create a group of variables each of which holds one value But with Petri nets we want to store arbitrarily many tokens in a place making this solution useless in many cases It would of course be possible to create a Java class with an appropriate set of fields to wrap a group of values but this would result in an excessive amount of
230. xtual format see above Like in Open Drawing a file selector dialog is displayed to let you determine the new file name and location After confirming with the OK button the specified file name is used to store the drawing now and during future invocations of Save Drawing The name of the drawing is set to the file name without path and file extension If you cancel or do not select an appropriate file name the drawing will neither be saved nor renamed Renew Dependent on the set of installed plug ins and on your window manager one of 2 0 several available drawing file types can be chosen from a drop down box in the dialog The effects are similar to the effects in the Open Drawing dialog explained above However the list of available file types is restricted by the type of the drawing you are going to save Save All Drawings This function saves all drawings that are currently in memory see Section 4 4 7 Before this can be done all untitled drawings have to be given a file name which is done as in 80 Save Drawing As see above If you cancel any of the save dialogues no drawing will be saved If all drawings are given a proper file name they are all saved You should invoke this function before you exit Renew see below Close Drawing Closes the active drawing window and removes the corresponding drawing from the list of drawings in memory see Section 1 4 7 Before doing so Renew checks if the drawing
231. y per line The net loader searches the directories in order from top to bottom In the list you can select one or more entries to manipulate On the right there are five buttons most of which affect the selected set of entries 99 Add opens a dialog where you can enter a new path entry The directory should be entered in os specific syntax If you want to specify a directory relative to the classpath check the appropriate box and make sure that the path does not start with a slash backslash drive letter or what else declares a path absolute at your operating system Edit opens a dialog similar to the Add dialog for each selected path entry Move up moves all selected entries one line above the first selected entry or to the top of the list if the topmost entry was included in the selection Move down moves all selected entries one line below the last selected entry or to the end of the list if the bottom most entry was included in the selection Delete removes all selected entries from the list Logging Renew This tab configures the simulation log traces see Menu entry Show simulation 2 trace below In contrast to other tabs changes to the settings on this tab take effect immediately It is possible to create additional loggers that focus on net transition or place specific parts of the simulation trace A click with the right mouse button on the top level entry of the logger tree opens a context

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