An Introduction to MetaUML
Contents
1. Class AC AN OQ Class B B B e A w 20 0 drawObjects A B Ovidiu Gheorghies B A Figure 3 Example of MetaUML Everything else works the same Point x int y int bb set x int y int getXQ int getYQ int debug C void DEE Figure 4 Class usage name attributes methods and visibility markers link inheritance B e A w endfig end From a user s perspective this is all there is to MetaUML With a reference describing how other UML elements are created one can set out to typeset arbit rary complex diagrams Class Diagrams A class is created as follows Class name class name list of attributes list of methods The suffix name gives a name to the Class ob ject which of course represents an UML class The name of the UML class is a string given by class name the attributes are given as a comma separated list of strings list of attributes the methods are given as a comma separated list of strings list of attributes The list of attributes and the list of methods may be void Each of the strings representing an attribute or a method may begin with a visibility marker for public for protected and for private MetaUML interprets this marker and renders a graphic stereotype in form of a lock which may be opened semi closed and closed respectively The following code yields the diagram in figur2. iPict foreColor 9 9 0 Class AC AN OQO Class B B QQ Class c C OQ C info foreColor 9 7 7 C info borderColor green C info iName iFont scale 2 positioning code ommited drawO0bjects A B C As an aside note that for each Class object its info member is created as a copy of iClass the actual An Introduction to MetaUML C Figure 32 Individual customization of a class object drawing is performed using this copied information Because of that one can modify the info member after the object has been created and still get the desired res ults Another thing worth mentioning is that the ClassInfo structure contains the iName member which is an instance of PictureInfo In our ex ample we do not want to modify the spacings around the Picture object but the characteristics of the font its contents is typeset into To do that we modify the iName iFont member which by default is a copy of iFont an instance of FontInfo defined in util_picture mp If for example we want to change the font the class name is rendered into we would set the attribute iName iFont name to a string representing a font name on our system as used with the MetaPost infont operator Predefined settings The third usage scenario is perhaps more interesting Suppose that we have two types of classes which we want to draw differently Making the setting adjust ments for each individual class ob
3. iBig bottom 1 iBig boxed 1 iBig ignoreNegativeBase 1 iBig iFont name defaultfont iBig iFont scale 3 PictureInfoCopy iSmall iPict iSmall boxed 1 iSmall borderColor green Below is an usage example of these definitions result in figure 26 Note the name of the macro EPicture The prefix comes form explicit and it s used to acknowledge that the how to draw informa tion is set explicitly as opposed to the Picture macro where the info member defaults to iPict EPicture a iBig yummy EPicture b iSmall cool you can still modify a info and b info b sw a se 10 0 drawObjects a b Stacking Objects It is possible to stack objects much in the style of setboxjoin from boxes library figure 27 Picture a0 yummy Picture ai cool Picture a2 fool setObjectJoin pa sw pb nw NAJAAR 2005 73 yummy cool fool Figure 27 Stacking objects fool cool yummy Figure 28 Grouping objects joinObjects scantokens listArray a 3 drawO0bjects scantokens listArray a 3 or drawObjects a0 al a2 The listArray macro provides here a shortcut for writing a0 al a2 This macro is particularly use ful for generic code which does not know beforehand the number of elements to be drawn Having to write the scantokens keyword is admittedly a nuisance but this is required The Grou
4. 2 A info iMethodStack spacing 17 A info iMethodStack bottom 10 drawObject A Both iAttributeStack and iMethodStack are in stances of PictureStackInfo which is used to con trol the display of PictureStack objects Conclusions MetaUML is a GNU GPL library for typesetting UML diagrams particularly useful in a TeX or LaTeX en vironment see Knuth 1986 Lamport 1994 It provides an easy to use human readable API The code of a diagram typeset in MetaUML ap pears clearer at least to the author of this paper than the corresponding code in uml sty pst uml sty umldoc or even XMI see Gjelstad 2001 Diamantini 1998 Palmer 1999 OMG 2003 It is the next best thing to using a visual tool while having the free 7 78 MAPS 33 dom of not becoming technologically dependent of any particular visual tool The util infrastructure of MetaUML offers means of defining and using objects which may recommend it for other typesetting projects unrelated to UML We mention here a few of its benefits the ability to stack and align text in a visually pleasing way a fine degree of control of how elements are laid out the ability to group objects while having access to the properties of inner elements a design pattern and syntactic sugar for writing modern looking reusable MetaPost code With this infrastructure in place it should be pos sible to extend MetaUML until it offers complete UML 2 0 support Re
5. is an equation which uses the item name to perform positioning Class P Person Class C Company drawing code ommited item aName iAssoc works for aName s 5 P w C w draw aName n aName n 20 20 label urt association name infont tyxtt aName n 20 20 However giving names to every association item may become an annoying burden especially when 68 MAPS 33 association name Person works for Company Figure 7 Referring to the properties of association items Person employee works for employer Tras l Company Figure 8 Anonymous association items Authenticate user by name password Figure 9 Usecase example there are many of them Because of this MetaUML also allows for anonymous items In this case the positioning is set by an equation which refers to the anonymous item as obj figure 8 P and C defined as in the previous example item iAssoc employee obj sw P e item iAssoc 1 obj nw P e other items are drawn similarly Use Case Diagrams Use Cases An use case is created by the macro Usecase Usecase name list of lines The list of lines is a comma separated list of strings These strings are placed on top of each other centered and surrounded by the appropriate visual UML notation Use case example result in figure 9 Usecase U Authenticate
6. to be drawn is recorded into an in stance of PictureInfo named iPict In this sec tion we present a case study involving the custom ization of Class objects The customization of any other MetaUML objects works similarly Here we can Ovidiu Gheorghies Figure 31 Changing the default settings for all classes not possibly present all the customization options for all kinds of MetaUML objects this would take too long Nevertheless an interested reader can refer to the top of the appropriate MetaUML library file where Info structures are defined For example class diagram re lated definitions are in metauml_class mp activity diagram definitions are in metauml_activity mp etc Global settings Let us assume that we do not particularly like the default foreground color of all classes and wish to change it so something yellowish In this scenario one would most likely want to change the appropriate field in iClass 9 9 0 After this the following code produces the result in figure 31 Class AC AN OQO Class B B QQ Class c C OQ iClass foreColor B w C n A e 20 0 5 A se B sw 0 10 drawO0bjects A B C Individual settings When one wants to make modifications to the settings of one particular Class objects another strategy is more appropriate How about having class C stand out with a light blue foreground color a bigger font size for the class name and a blue border figure 32
7. 0 0 drawObject A In A nw we refer to the north west of the class rectangle that is to its upper left corner In general every MetaUML object has the positioning properties given in figure 2 These properties are used to set where to draw a given object whether by assigning them absolute values or by setting them relatively A Class diagram Client interface Component Operation Add Component Remove Component GetChild int Leaf Composite Operation Operation Add Component Remove Component GetChild int B Activity diagram Eat something good from the kitchen still hungry Read a book Listen to music and ignore it C Use case diagram User Authenticate by username password Query database Authenticate user Authenticate by smartcard Database D State machine diagram Working Reading commands Preparing error report error Writing result Figure 1 UML diagrams created by MetaUML 66 MAPS 33 top nw n jue Test al height Wwem a2 Ce e a3 aLongMethodQ void bottom SW fse width left right Figure 2 Positioning properties of any MetaUML object here a class object is depicted to other objects Suppose that we have defined two classes A and B The
8. Ovidiu Gheorghies NAJAAR 2005 65 An Introduction to MetaUML Exquisite UML Diagrams in MetaPost Abstract MetaUML is a GNU GPL MetaPost library for typesetting exquisite UML Unified Modeling Language diagrams MetaUML offers a highly customizable object oriented API designed with the ease of use in mind This paper presents usage examples as well as a description of MetaUML infrastructure This infrastructure may prove useful for general MetaPost typesetting providing object oriented replacements and enhancements to functionalities offered by the boxes package Keywords MetaPost TeX LaTeX UML class diagram state machine diagram use case diagram activity diagram Introduction Figure 1 presents a gallery of diagrams created by MetaUML Gheorghies 2005 The code which generates these diagrams is quite straightforward combining a natural object oriented parlance with the power of MetaPost equation solving for more information on MetaPost see Hobby 1992 An UML class for example can be defined as fol lows Class A MyClass C attri int attr2 int methodi void methodi void This piece of code creates an instance of Class which will be afterward identified as A This object has the following content properties aname MyClass a list of attributes attri attr2 and a list of methods method1 method2 The one thing remaining before actually drawing A is to set its location A nw
9. begin and the end of an activity diagram can be marked by using the macros Begin and End respect ively The constructors of these visual objects take no parameters Begin beginName End endName Figure 12 gives the output of the code Begin b End e b nw 0 0 e nw 20 20 drawO0bjects b e An Introduction to MetaUML Figure 12 Begin and end in an activity diagram Learn MetaUML the MetaPost UML library Figure 13 Activity example Take order Figure 14 State example Activity An activity is constructed as follows Activity name list of strings The parameter list of strings is a comma sep arated list of strings These strings are centered on top of each other to allow for the accommodation of a longer activity description within a reasonable space An example is given in figure 13 Activity A Learn MetaUML the MetaPost UML library drawObject A Types of Links In activity diagrams transitions between activities are needed They are typeset as in the example below Fig ure 15 shows such a transition rendered This type of link is also used for state machine diagrams link transition pointA pointB State Diagrams The constructor of a state allows for aggregated sub states State name state name substates list The parameter state name is a string or a list of comma separated strings representing the state s name or description The substa
10. ct boxed 1 PictureStack myStack foo bar int infont tyxtt nicely centered infont defaultfont nice vcenter drawObject myStack Note the last parameter of the macro PictureStack here vcenter It is used to gen erate appropriate equations based on a descriptive name The spacing between individual picture objects is set by the field iStack spacing Currently the fol lowing alignment names are defined vleft vright vcenter vleftbase vrightbase vcenterbase All these names refer to vertical alignment the prefix y alignment can be at left right or centered The variants having the suffix base align the pictures so that iStack spacing refer to the distance between the bottom lines of the pictures The unsuffixed vari ants use iStack spacing as the distance between one s bottom line and the next s top line The base alignment is particularly useful for stacking text since it offers better visual appearance when iPict ignoreNegativeBase is set to 1 Components Design Each MetaUML component e g Picture PictureStack Class is designed according to an established pattern This section gives more insight on this In order to draw a component one must know the following information what to draw or what are the elements of a component how to draw or how are the elements positioned Ovidiu Gheorghies in relation to each other within the component wher
11. drawMethod and the heads with the meth ods iLink drawMethodA and iLink drawMethodB 76 MAPS 33 respectively figure 30 Object Definitions Easier generic_declare In MetaPost if somebody wants to define something re sembling a class say Person he would do something like this vardef Person expr _name _age prefix can be seen as this pointer string name numeric Q age name _name age _age enddef This allows for the creation of instances or objects of class Person by using declarations like Person personA Person personB However if one also wants to able able to create indexed arrays of persons such as Person student0 Person student1 etc the definition of class Person must read vardef Person expr _name _age z str generic_declare string _n name generic_declare numeric _n age n_ name _name age _age enddef This construction is rather inelegant MetaUML of fers alternative macros to achieve the same effect un cluttering the code by removing the need for the unaes thetic _n_ and _n vardef Person expr _name _age attributes 0 var string name var numeric age name _name age _age enddef Customization in MetaUML Examples We have seen that in MetaUML the how to draw information is memorized into the so called Info structures For example the default way in which a Picture object is
12. e 4 Class A Point x int y int set x int y int eetX int eetY int debug void drawObject A An Introduction to MetaUML interface home User Figure 5 Class usage stereotypes Vector Figure 6 Class usage templates Stereotypes After a class is created its stereotypes may be specified by using the macro classStereotypes classStereotypes name list of stereotypes Here name is the object name of a previously cre ated class and list of stereotypes is a comma separated list of strings Here is an example along with the resulting diagram figure 5 Class A User OQ classStereotypes A lt lt interface gt gt lt lt home gt gt drawObject A Parametrized Classes Templates The most convenient way of typesetting a class tem plate in MetaUML is to use the macro ClassTemplate This macro creates a visual object which is appropri ately positioned near the class object it adorns ClassTemplate name list of templates class object The name is the name of the template object list of templates is a comma separated list of strings and the class object is the name of a class object The code below results in the diagram from figure 6 Class A Vector QQ ClassTemplate T T size int A drawObjects A T The macro Template can also be used to create a template object but
13. e it wouldn t have been possible to modify the margins as in the code below question 1 what to draw Picture pict foo question 2 how to draw pict info left 10 pict info boxed 1 question 3 where to draw pict nw 0 0 An Introduction to MetaUML y now we can draw drawObject pict To allow for this type of code the equations that define the layout of the Picture object here what the margins are must be defined somewhere after the constructor This is done by a macro called Picture_layout This macro defines all the equa tions which link the what to draw information to the how to draw information which in our case is taken from the info member a copy of iPict Neverthe less notice that Picture_layouts is not explicitly in voked To the user s great relief this is taken care of automatically within the Picture_draw macro There are times however when explicitly invoking a macro like Picture_layout becomes a necessity This is because by contract it is only after the layout macro is invoked that the final dimensions width height of an object are definitely and permanently known Imagine that we have a component whose job is to surround in a red filled rectangle some other ob jects This component needs to know what the dimen sions of the contained objects are in order to be able to set its own dimensions At drawing time the contained objects must not have been drawn a
14. e to draw For example in order to draw a picture object we must know respectively what is the text or the native picture that needs to be drawn what are the margins that should be left around the contents where is the picture to be drawn Why do we bother with these questions Why don t we just simply draw the picture component as soon as it was created and get it over with That is why doesn t the following code just work Picture pict foo Well although we have the answer to question 1 what to draw we still need to have question 3 answered The code below becomes thus a necessity actually you are not forced to specify the positioning of an object because its draw method positions it to 0 0 by default question 1 what to draw Picture pict foo question 3 where to draw pict nw 10 10 now we can draw drawObject pict How about question 2 how to draw By default this problem is addressed behind the scenes by the component This means for the Picture object that a native picture is created from the given string and around that picture certain margins are placed by means of MetaPost equations The margins come in handy when one wants to quickly place Picture ob jects near others so that the result doesn t look too cluttered If these equations were defined within the Picture constructor then an usability problem would have appeared becaus
15. ferences Roegel D 2002 The METAOBJ tutorial and reference manual Available from www loria fr roegel TeX momanual pdf Knuth D E 1986 The Txxbook Addison Wesley Publishing Company Ovidiu Gheorghies Faculty of Computer Science Al Cuza University of la i Romania ogh info uaic ro Ovidiu Gheorghies Lamport L 1994 LaTX a Document Preparation Sys tem Addison Wesley Publishing Company 2nd edi tion Gheorghies O 2005 MetaUML Tutorial Reference and Test Suite Available from http metauml sourceforge net Hobby J 1992 A User s Manual for MetaPost Avail able from http www tug org tutorials mp Gjelstad E 2001 uml sty 0 09 09 Available from http heim ifi uio no ellefg uml sty Diamantini M 1998 Interface utilisateur du package pst uml Available from http perce de LaTeX pst um1 Palmer D 1999 The umldoc UML Doc umentation Package Available from http www charvolant org elements XML Metadata Available from Object Management Group 2003 Interchange XMI Specification http www omg org
16. ghies gt B LT Figure 18 Manhattan paths can choose to reverse it by using rpathManhattanX and rpathManhattanY note the prefix r pathManhattanX A B pathManhattanY A B rpathManhattanX A B rpathManhattanY A B Figure 18 shows these macros at work Class AC AN OQ Class B B QQ B sw A ne 10 10 drawO0bjects A B link aggregationUni rpathManhattanX A e B s link inheritance pathManhattanY A n B w Stair Step Paths These path macros generate stair like paths between two points The stair can rise first in the direction of Ox axis pathStepX or in the direction of Oy axis pathStepY How much should a step rise is given by an additional parameter delta Again the mac ros prefixed with r reverse the direction of the path given by their unprefixed counterparts pathStepX A B delta pathStepY A B delta rpathStepxX A B delta rpathStepY A B delta Figure 19 shows these macros at work stepX 60 link aggregationUni pathStepX A e B e stepX stepY 20 link inheritance pathStepY B n A n stepY Horizontal and Vertical Paths There are times when drawing horizontal or vertical links is required even when the objects are not prop erly aligned To this aim the following macros are use An Introduction to MetaUML Figure 19 Stair step pa
17. high level ob jects infrastructure along with a battery of predefined objects Surprisingly enough MetaUML does not use METAOBJ Instead it uses a custom written light weight object oriented infrastructure provisionally called util The fact that METAOBJ s source con sists of a huge file which is rather hard to follow and understand contributed to this decision Another library that has some object oriented traits is the boxes library which comes with the standard MetaPost distribution Early versions of MetaUML did use boxes as an infrastructure but eventually it had to be abandoned The main reason was that it was difficult to achieve good visual results when stacking texts more on that further on Also it had a degree of flexibility which became apparent to be insufficient Motivation Suppose that we want to typeset two texts with their bottom lines aligned using boxit figure 23 boxit a yummy boxit b cool a nw 0 0 b sw a se 10 0 drawboxed a b or drawunboxed a b draw a sw b se dashed evenly withpen pencircle scaled 1 1 Note that yummy looks slightly higher than cool this is unacceptable when in an UML class diagram roles are placed at the ends of a horizontal association Regardless of default spacing being smaller in the util library the very same unfortunate misalignment effect rears its ugly head figure 24 Picture a yummy Picture b cool co
18. ject would soon be come a nuisance MetaUMIs solution consists in the ability of using predefined how to draw Info objects Let us create such objects ClassInfoCopy iHome iClass iHome foreColor 0 9 9 ClassInfo iRemote iRemote foreColor 9 9 0 iRemote borderColor green Object iHome is a copy of iClass as it might have been set at the time of the macro call Object iRemote is created just as iClass is originally created We can now use these Info objects to easily set the how to draw information for classes The result is depicted in figure 33 please note the E prefix in EClass EClass A iHome UserHome EClass B iRemote UserRemote O EClass C iHome CartHome EClass D iRemote CartRemote 0 O NAJAAR 2005 Figure 33 Using predefined settings Foo a int b int fool bar gar b b b b ib Figure 34 Extreme customization of a class You may want not to do this after all Extreme customization When another font or font size is used one may also want to modify the spacings between the attributes and methods baselines Figure 34 is the result of the unlikely code Class A Foo a int b int fooQ barQ gar A info iAttributeStack iPict iFont scale 0 8 info iAttributeStack top 10 A info iAttributeStack spacing 11 bad A info iMethodStack iPict iFont scale
19. lready because the red rectangle of the container would overwrite them Therefore the whole pseudo code would be Create objects o1 02 Ok Create container c ol 02 Ok Optional modify info s for o1 02 ok Optional modify info for c layout c requiring layout of o1 02 OK establish where to draw c draw red rectangle defined by c draw components 01 02 ok within c Note that an object mustn t be laid out more than once because otherwise inconsistent or superfluous equations would arise To enforce this by contract any object must keep record of whether its layout method has already been invoked and if the answer is affirmative subsequent invocations of the layout macro would do nothing It is very important to men tion that after the layout macro is invoked over an object modifying the info member of that object has no subsequent effect since the layout equations are declared and interpreted only once Notes on the Implementation of Links MetaUML considers edges in diagram graphs as links A link is composed of a path and the heads possible none one or two For example an association has no heads and one must simply draw along the path with a solid pen An unidirectional aggregation has a solid path and two heads one is an arrow and the other is NAJAAR 2005 75 AB the path specified by the user AA iLink widtha BB iLink widthB Ca Figure 30 Details on how a link is d
20. mment next line for unboxed a info boxed b info boxed 1 b sw a se 10 0 drawObjects a b However the strong point of util is that we have a recourse to this problem figure 25 Ovidiu Gheorghies yummy _ cool yummy cool Figure 24 Misalignment occurs by default with the util library but this can be configured not to happen ummy _ cool yummy __ cool Figure 25 The util package provides good alignment iPict ignoreNegativeBase 1 Picture a yummy Picture b cool the rest the same as above drawO0bjects a b The Picture Macro We have seen previously the line iPict ignoreNegativeBase 1 Who is iPict and what is it doing in our program MetaUML aims at separating the business logic what to draw from the interface how to draw In order to achieve this it records the how to draw information within the so called Info structures The object iPict is an instance of PictureInfo structure which has the following properties or attributes left right top bottom ignoreNegativeBase boxed borderColor The first four attributes specify how much space should be left around the actual item to be drawn The marvelous effect of ignoreNegativeBase has just been shown off while the last two attributes control whether the border should be drawn when boxed 1 and if drawn in which color There s one more thing the font to typeset the text in This is specified in a F
21. n the following code would give a conceivable positioning A nw 0 0 B e A w 20 0 After the objects are drawn one may draw links between them such as inheritance or association rela tions between classes in class diagrams or transitions between states in state machine diagrams Whichever the purpose is MetaUML provides a generic way of drawing an edge in a diagram s graph link how to draw information path to draw The how to draw information is actually an object which defines the style of the line e g solid dashed and the appearance of the heads e g nothing ar row diamond One such object called inheritance defines a solid path ending in a white triangle The path to draw parameter is simply a MetaPost path For example the following code can be used used to represent that class B is derived from A link inheritance B e A w Note that the direction of the path is important and MetaUML uses it to determine the type of adornment to attach at the link ends if applicable In our ex ample a white triangle denoting inheritance points towards the end of the path that is towards class A To sum up we present a short code and the result ing diagram figure 3 This is typical for everything else in MetaUML The positioning of A does not need to be explicitly set because floating objects are auto matically positioned at 0 0 by their draw method input metaum1 beginfig 1
22. ont Info structure which has two attributes the font name and the font scale This information is kept within the PictureInfo structure as a contained attribute iFont Both FontInfo and PictureInfo have copy constructors which can be used to make copies We have already the effect of these copy constructors at work when we used Picture a yummy a info boxed 1 A copy of the default info for a picture iPict has been made within the object a and can be accessed as a info Having a copy of the info in each object may seem like an overkill but it allows for a fine grained control of the drawing mode of each individual object An Introduction to MetaUML umm cool Figure 26 Having predefined configurations yields short convenient code This feature comes in very handy when working with a large number of settings as it is the case for MetaUML Let us imagine for a moment that we have two types of text to write one with a small font and a small mar gin and one with a big font and a big margin We could in theory configure each individual object or set back and forth global parameters but this is far for conveni ent It is preferable to have two sets of settings and specify them explicitly when they are needed The fol lowing code could be placed somewhere in a configur ation file and loaded before any beginfig macro PictureInfoCopy iBig iPict iBig left iBig right 20 iBig top 10
23. p Macro It is possible to group objects in MetaUML This fea ture is the cornerstone of MetaUML allowing for the easy development of complex objects such as compos ite stats in state machine diagrams Similarly to the macro Picture the structure GroupInfo is used for specifying group properties its default instantiation is iGroup Furthermore the macro EGroup explicitely sets the layout information Figure 28 results from the code below iGroup left 20 iGroup right 15 iGroup boxed 1 iPicture boxed 1 Picture a yummy Picture b cool Picture c fool a nw 20 20 AA a nw 15 40 B b nw c nw Group g a b c g nw 10 10 C drawObject g Note that after some objects are grouped they can all be drawn by invoking the draw0bject macro solely on the group that aggregates them Another import ant remark is that it is necessary only to set the relat ive positioning of objects within a group line A and 74 MAPS 33 foo bar int nicely centered nice Figure 29 An example of a picture stack B afterward one can simply move the group to a given position line C and all the contained objects will move along The PictureStack Macro The PictureStack macro is a syntactic sugar for a set of pictures stacked according to predefined equations and grouped together figure 29 iStack boxed 1 iStack iPi
24. rawn by MetaUML a diamond So the template algorithm for drawing a link is 0 Reserve space for heads 1 Draw the path except for the heads 2 Draw head 1 3 Draw head 2 Each of the UML link types define how the drawing should be done in each of the cases 1 2 and 3 Con sider the link type of unidirectional composition Its class is declared as vardef CompositionUniInfo LinkInfo widthA defaultRelationHeadWidth heightA defaultRelationHeadHeight drawMethodA drawArrow widthB defaultRelationHeadWidth heightB defaultRelationHeadHeight drawMethodB drawDiamondBlack drawMethod drawLine enddef Using this definition the actual description is cre ated like this CompositionUniInfo compositionUni As shown previously is is the macro link which performs the actual drawing using the link descrip tion information which is given as parameter gener ally called iLink For example we can use link aggregationUni 0 0 40 0 Let us see now the inner workings of macro link Its definition is vardef link text iLink expr myPath LinkStructure 1s myPath iLink widthA iLink widthB drawLinkStructure 1s iLink enddef First space is reserved for heads by shortening the given path myPath by iLink widthA at the be ginning and by iLink widthB at the end After that the shortened path is drawn with the method given by iLink
25. sting state which is worth mentioning OnEntry Open eyes OnExit Sleep well Figure 16 State example internal transitions Figure 17 Link paths can be arbitrary complex in MetaUML the heads are properly drawn Special States Similarly to the usage of Begin and End macros one can define history states exit entry point states and terminate pseudo states by using the following con structors History nameA ExitPoint nameB EntryPoint nameC Terminate nameD Drawing Paths The link macro is powerful enough to draw relations following arbitrary paths figure 17 za 10 10 zb 80 10 path cool cool za za 20 10 zb 20 40 zb 10 30 zb link aggregationUni cool Regardless of how amusing this feature might be it does become a bit of a nuisance to use it in its bare form When typesetting UML diagrams in good style one generally uses rectangular paths It is for this kind of style that MetaUML offers extensive support provid ing a syntactic sugar for constructs which can other wise be done by hand but with some extra effort Manhattan Paths The Manhattan path macros generate a path between two points consisting of one horizontal and one vertical segment The macro pathManhattanX generates first a horizontal segment while the macro pathManhattanY generates first a vertical segment In MetaUML it also matters the direction of a path so you Ovidiu Gheor
26. tA objectB Here thePath is a given MetaPost path and objectA and objectB are two MetaUML objects By contract each MetaUML object of type say X defines a macro X_border which returns the path that sur rounds the object Because of that pathCut can make the appropriate modifications to thePath The following code demonstrates the benefits of the pathCut macro figure 21 z A se 30 10 link transition pathCut A B A c z B c Direct Paths between Centers At times is quicker to just draw direct paths between the center of two ob jects minding of course the object margins The macro which does this is clink clink how to draw information objA objB The parameter how to draw information is the same as for the macro link objA and objB are two MetaUML objects Figure 22 gives the output of the following code clink inheritance A B The MetaUML Infrastructure MetaPost is a macro language based on equation solv ing Using it may seem quite tricky at first for a pro grammer accustomed to modern object oriented lan guages However the great power of MetaPost con sists in its versatility Indeed it is possible to write a 71 72 MAPS 33 yummy _ cool yummy cool Figure 23 Motivation for not using boxes the bottom alignment is imperfect system which mimics quite well object oriented beha vior Along this line METAOBJ Roegel 2002 is a library worth mentioning it provides a
27. tes list parameter is used to specify the substates of this state as a comma separated list of objects this list may be void Figure 14 presents a simple state rendered by the following code State s Take order drawObject s NAJAAR 2005 69 Composite Component Figure 15 State example composite states Composite States A composite state is defined by enumerating at the end of its constructor the inner states Interestingly enough the composite state takes care of drawing the sub states it contains The transitions must be drawn after the composite state as seen in the next example figure 15 Begin b End e State c Component State composite Composite b e c b midx e midx c midx c top b bottom 20 e top c bottom 20 composite info drawNameLine 1 draw0bject composite link transition b s c n link transition c s e n Internal Transitions Internal transitions can be specified by using the macro stateTransitions name list transitions Identifier name gives the state object whose in ternal transitions are being set and parameter list transitions is a comma separated string list Figure 16 presents the result of the code below State s An interesting state which is worth mentioning O stateTransitions s OnEntry Open eyes OnExit Sleep well s info drawNameLine 1 draw0bject s 70 MAPS 33 An intere
28. this time the resulting object can be positioned freely Template name list of templates Of course one can specify both stereotypes and tem plate parameters for a given class Types of Links In this section we enumerate the relations that can be drawn between classes by means of MetaUML macros NAJAAR 2005 67 Suppose that we have the declared two points A on the left and B on the right pair A B A 0 0 B 50 0 Bidirectional association link association A B Unidirectional association link associationUni A B Inheritance link inheritance A B gt Aggregation link aggregation A B Unidirectional aggregation link aggregationUni A B Composition link composition A B __ Unidirectional composition link compositionUni A B lt e Associations In UML an association typically has two of association ends and may have a name specified for it In turn each association end may specify a multiplicity a role a visibility an ordering These entities are treated in MetaUML as pictures having specific drawing inform ation spacings font The first method of creating association items is by giving them explicit names Having a name for an association item comes in handy when referring to its properties is later needed see the non UML compliant diagram in figure 7 Note that the last parameter of the macro item
29. ths C foo int untilY B A ab untilX Figure 20 Horizontal and vertical paths ful pathHorizontal pA untilX pathVertical pA untilY rpathHorizontal pA untilX rpathVertical pA untilY A path created by pathHorizonal starts from the point pA and continues horizontally until coordinate untilX is reached The macro pathVertical con structs the path dually working vertically The prefix r reverses the direction of the path Figure 20 gives an usage example untilX B left link association pathHorizontal A e untilX untilY C bottom link association pathVertical A n untilY Direct Paths A direct path can be created with directPath The call directPath A B is equivalent to A B Paths between Objects Using the constructs presented above it is clear that one can draw links between diagram objects using a code like link transition directPath objA nw objB se NAJAAR 2005 Figure 21 The pathCut macro at work B Figure 22 Direct linking between objects with clink There are times however this may yield unsatisfact ory visual results especially when the appearance of the object s corners is round MetaUML provides the macro pathCut whose aim is to limit a given path ex actly to the region outside the actual borders of the objects it connects The macro s synopsis is pathCut thePath objec
30. user by name password drawObject U Actors An actor is created by the macro Actor Actor name list of lines Here list of lines represents the actor s name For convenience the name may be given as a list of strings which are placed on top of each other to provide support for the situations when the role is quite long Otherwise giving a single string as an ar gument to the Actor constructor is perfectly fine Actor example result in figure 10 Ovidiu Gheorghies User Figure 10 Actor example Administrator Figure 11 Actor example accessing the human Actor A User drawObject A Note that one may prefer to draw diagram relations positioned relatively to the visual representation of an actor the human rather than relatively to the whole actor object which also includes the text Because of that MetaUML provides access to the human of every actor object actor by means of the sub object actor human Figure 11 gives the result of the code below Actor A Administrator drawObject A draw objectBox A draw objectBox A human Note that in MetaUML objectBox X is equival ent to X nw X ne X se X sw cycle for every object X Types of Links Some of the types of links defined for class diagrams such as inheritance association etc can be used with similar semantics within use case diagrams Activity Diagrams Begin and End The
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