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1. Document D E a The application will be include in a panel like all the other My Sidebar functionality You can see three different tabs main enlarged preferences on the top of this panel They allow you to choose what kind of operation you want to execute 20 5 1 2 The main panel The main panel is the default panel It allows you to do all the needed operations on the metadata It is separated into three different parts N Aalborg University Esbjerg Netsc m A File Edit View Search Bookmarks Tasks Help far E 2 5 ww IN N Sidebar Tabs gt E Metadata service BS university ESBJERG r Display Auto Update epage of Aalborg University Esbjerg GREEN Index of available information E i gt Education select ee value gt Research key16 value12 E People l l key14 value121 gt Computing Services loup petit d gt Calendar gt Student information keyat valeti gt Esbjerg information keys valueiz gt gt Tilbud til gymnasier HTX keya valued b Nye stillinger key3 value Tel 45 7912 7666 University Canteen v Fax 45 7545 3643 Email mst Que ac de key BE this page fo the webmaster y Current url lay August 02 2000 09 45 54 http if wwwaue auc dk Document Done 5 1 2 1 The display section This section permits you to choose if you want to see new metadata each time you load a new web page If you check the2. You can add a value by giving its name and value and pressing the add button If you want to update a key it is the same method a confirm box will just ask you if the update should be done The value of a key could be found by filling in the name field and pressing the find button If this key is recorded in the database the value will be displayed in the value field fe Construct Metadata Viewer Update URL Selected value19 belgium value12 value121 petit value11 value12 value4 LUI A no address no host 25 5 2 2 The enlarged data panel If the value of a key is very large it is easier to read it in the enlarged data panel You can select the name of the key of your choice in a scroll menu Then the value of the selected key will automatically be displayed in a large field This value can be changed and updated by pressing the update button E Construct Metadata Viewer no address no host 26 5 2 3 The preferences panel The third panel is exactly the same as the Netscape 6 one You can choose which metadata server to use You should fill in the address and the port number fields and press the apply button If you want to restore the default parameters in order to be connected to the default server you just have to press the default field EJ Construct Metadata Viewer Metadata Enlarged datas Preferences Server prefe
3. and the binding to XPCOM components is provided by a library called XPConnect The Java Virtual Machine communicates with Mozilla Netscape through the Object Java Interface Applet An applet would allow the functionality to be easily integrated to a web page situated in the Netscape My Sidebar for example This solution requires a Swing or AWT Java interface It will be easier if necessary to port this extension to Internet Explorer but it seems to be a less integrated solution For JavaScript to be able to control a Java applet the Java applet must provide public methods The methods of an applet are the functions which are associated with its class Public methods are functions which are externally visible and can be called by other Java classes and by JavaScript Well written Java applets will provide public methods to make basic properties readable and writeable by other code This makes it possible to customize and reuse existing Java applets without modifying the applet s source code 3 2 1 2 The better choice at the moment The applet The three solutions found have advantages and drawbacks Integrating a Java plugin is more useful when you have to use a specific data format especially for multimedia and interactive Applet extension is more portable if you need in the future to develop the Construct services for another browser The Java application seems to permit a good integration to the Netscape 6 navigator Furthermore it al
4. UPDATE_RECORD Update metadata record DELETE RECORD Delete metadata record GET_KEY Get metadata key ADD_KEY Add metadata key UPDATE_KEY Update metadata key DELETE_KEY Update metadata key 4 2 2 Connection class The Connection class is the class which knows parameters about the metadata server The two main attributes are the hostname and the port number This is the class that will make the 16 connection with the server and which will try to reconnect if there is a problem Connections will be done using TCP IP two attributes of the class are socket descriptors By default connections will be established with the localhost address and on the port 16000 but there are different constructors which allow to choose the ports at the instantiation instant 4 2 3 Metadata class The Metadata class represents metadata handled by the application Normally it is a character string being used as key associated with another one corresponding to the value of the metadata We can imagine that in the future other data like pictures or video sequences could be used instead of characters Normally in this case the metadata class would be the only class to change the other classes deal with the data via the getMetadataValue method which will return an Object class derived object 4 2 4 Swinginterface class The Swinginterface class provides the methods used by the Swing interface that is by the standalone application The ja
5. auto update button it will be done automatically Otherwise you will have to use the refresh button to get metadata for the new web page 5 1 2 2 The metadata section This section shows you all keys and values of the web page When there are too many keys you can put your mouse over two scroll buttons at the top and bottom of the list and it will automatically show you the other data 21 Add a key If you want to add a key you enter the name of the new key in the key field and press the add button Then it will switch to the enlarged panel where you will have to enter the value of your key and to confirm your operation Update a key A key can be updated by selecting it or by entering its name in the key field Then when you press the update button you will see the value of this key in the enlarged panel and it will be possible to modify it Delete one or more key s You can delete one or more keys by checking their select buttons and pressing the delete button It is also possible to enter the name of the key you want to delete in the key field and then press delete Find or enlarge the display of a key value The main panel displays all the keys and values of a web page so it could be difficult to find a key in the list or to read a value because of the size of the cells If you select a key or enter its name and press the find button then the key and its value will be displayed in the enlarged panel and it will be easy to read
6. the NAME attribute of the lt applet gt tag for example the format for code is document applets theAppletName theMethod This technique is use to transmit the URL of the web page to the applet and the metadata when the user has chosen an XUL interface Use Java code to access JavaScript methods and properties On the Java side JavaScript objects are wrapped in an instance of the class Netscape Javascript JSObject and passed to Java If we want to include JavaScript objects in Java we must import this netscape javascript package into our Java file It contains the additional object model JSObject that can be used from within a Java applet to access JavaScript objects in a document When a JSObject is sent from Java to JavaScript the runtime engine unwraps it to its original JavaScript object type The general format for code is JSObject objectname method or JSObject objectname property 18 It provides the ability to transmit metadata from the server to the JavaScript document by using the Java applet These metadata could be easily displayed thanks to the XUL interface in the sidebar 4 2 8 Installation procedure XPI package A set of Ul objects including the description of its structure appearance behavior and localizable strings is called a package Sample packages in the Communicator product include Navigator Messenger Preferences Bookmarks and Composer Packages can communicate with one another and may sha
7. the value of this key 5 1 2 3 The current URL section The field of this section just reminds the user of the URL of the current metadata If the auto update button is checked this URL will change when a new web page is loaded 22 5 1 3 The enlarged panel The second panel has three parts It allows you to do the same operations as the main panel You can directly add or update a key if you enter its name and its value in the two fields key and value You are also able to find the value of a key or delete it by giving its name The URL of the key is displayed at the bottom of the interface like in the main panel However this URL will always be the same because it depends on the key and not on the current URL Ml Google Netsc ape 6 A File Edit View Search Go Bookmarks Tasks Help LAB MAGA Se http www qoogle com My Sidebar Metadata service Goog Search 1 346 966 Value Regional Asia Europe North merica _ Google Search Science Biology Psychology Physics honni Google Web Directory opping g Autos Clothing Gifts the web organized by topic Society Issues People Religion Advertise instantly With a credit card your ad goes on Google today Enartoe Casa Copiate Come Crna Uri Cool Jobs Add Google to Your Site http www google com Advertise with Us Google in your 23 5 1 4 The preferences panel The third panel allows you to choose which metadata ser
8. without losing track of what he is browsing in the main window Multi task is permitted Because it uses a Java applet users can separate the program from the sidebar and drop it where he prefers on his desktop Sidebar s drawbacks For developers there are some restrictive rules to respect Although any file format that the Navigator 6 browser can display can appear in My Sidebar these files will have to display well in a window that is smaller than 170 pixels wide by 150 pixels tall When designing the My Sidebar tab we must be sure that information is presentable in a small space and responds well to being resized by the user The default width of My Sidebar is 170 pixels wide The content area is 162 pixels wide 144 pixels wide when a scroll bar is included You can effectively utilize the space within the My Sidebar area by decreasing font 10 sizes The tab title width is approximately 20 variable width western characters or 10 double byte characters A good integration to Netscape 6 The interface between users and the Construct metadata structural service could be implemented in many ways We have decided to design two different interfaces for many reasons The first one is made in XUL This language is used in Netscape 6 to display the browser interface The sidebar gets the same look as the browser so it is the default interface In this case we have to use a hidden applet located in the sidebar The URL of the web page and me
9. Providing Metadata Services on the World Wide Web Yann Neveu Youenn Guervilly Uffe K Wiil David L Hicks E oF N ESBJERO Technical Report CSE 01 01 Dept of Computer Science and Engineering Aalborg University Esbjerg Niels Bohrs Vej 8 6700 Esbjerg Denmark Address Dept of Computer Science and Engineering Aalborg University Esbjerg Niels Bohrs Vej 8 6700 Esbjerg Denmark Email dept cs aue auc dk Web www cs aue auc dk Phone 45 7912 7666 Fax 45 7545 3643 Table of Contents n d ET spot 4 CONS A aa aaa Ee 5 oF E 8 ST NESAS naeran aa a EE e 8 3 2 Means EE 8 4 Design ll Ria 13 GT en WEE 13 2 Class diagram aiii laid da ia 16 AA A A eil 20 5 1 The Netscape 6 interface senge once ii iii 20 5 2 The standalone application aii as 25 6 COMGIU SION EE 28 References ciale ella 29 1 Introduction Yann Neveu and Youenn Guervilly two Socrates exchange students from the University of Bretagne in Brest France carried out the work described in this report during a three month practicum at the Department of Computer Science and Engineering Aalborg University Esbjerg Denmark Uffe K Wiil and David L Hicks supervised the project which was carried out in the context of the Construct research project www cs aue auc dk construct The purpose of the project was to provide metadata services on the World Wide Web WWW We have extended Netscape 6 with additional functionality and made it an appl
10. data application Section 6 concludes the report 2 Construct The Construct research project www cs aue auc dk construct is concerned with providing different services to help users manage and structure their knowledge The Construct environment consists of different categories of software components e p e Applications This category includes desktop applications eg Netscape MS Word and Emacs that have been integrated modified extended or wrapped to be able to make use of the Construct structure services e Wrapper services A wrapper is a service that allows a legacy application to be integrated with the Construct environment Natively compliant applications do not need wrappers all other applications do e Structure services Integrated applications can make use of different types of structure services to organize data located in data stores Each type of structure service provides a different set of structural abstractions e g navigational spatial taxonomic argumentation workflow and collaboration that supports different application domains e Foundation services Foundation services provide the very basic services in the environment that most other services depend on Example foundation services are o Structure stores A structure store is a software component that manages storage and retrieval of structure Structure stores can handle different types of structural abstractions o Multiuser and collabora
11. e For the moment until the next release of the browser the XPCOM capabilities are not available for a Netscape external Java application However when it is available this standalone program will be linked with Netscape without having to develop another user interface The user may choose to consult metadata about a specific URL without having to launch the Netscape 6 browser which is a very heavy application in terms of memory and processor use Swing or AWT interface We had to choose between two types of Java GUI API In fact there is the old one AWT and the layer above it more recent the Swing API The Swing API is available only in the more recent releases of the Java runtime environment The main goal of the project is to make an extension for the Netscape 6 browser With this browser is bundled the Java 2 runtime environment Because this version of Java was available with Version 6 of the browser we have decided to use the Swing API 4 1 1 3 The same code for the applet and for the application Using the Inprise Jbuilder integrated development environment there is an option during the project creation process that provides the opportunity to add a Boolean parameter to the 13 skeleton code of the Core class which is called isStandalone This attribute will be initialized at the Core instance creation If the code is launched as an applet the init method will be called at the beginning So in the init method
12. e services For example UML Tool and Emacs are clients of the navigational structure service Thus it is possible to link from classes or fields in the UML diagrams to for example design rational located in a text file under the control of Emacs The specific instance of the Construct environment in which the present WWW metadata project has been taking place is depicted below The darker shaded boxes green boxes when printed in color indicate the components directly involved in the project wrapper wrapper dii navigational structure structure services service foundation services When the present project began the Construct metadata service was already in place It was being used by the Emacs editor through a wrapper service to provide metadata support for Emacs files Briefly stated the goal of this project was to integrate Netscape 6 into the Construct environment using a similar wrapper and to then use the metadata service to provide metadata support for web pages 3 Analysis 3 1 Needs One part of the construct project is to provide metadata on different documents to users which consult them using different software One type of document is the web page which is consulted via a browser The functionality which has to be added to the browser is an extension which must permit the consultation of the Construct metadata server The Netscape 6 browser has been chos
13. en because of its availability on most platforms Another advantage of this browser is the possibility to get the source code The Java language permits to make an extension which can run on most of platforms Moreover it keeps a certain integrity with the other parts of the Construct project which are Java components 3 2 Means 3 2 1 How to extend Netscape 6 with Java The Mozilla Project Since 1998 the main part of the Netscape development has been done in the Mozilla project The Mozilla project is based on the open source code of the former Netscape 5 project At the end of 2000 the first version of the Communicator suite was issued from the Mozilla code i e browser mail client and has been distributed it is called Netscape 6 Netscape 6 status Netscape 6 is based on the status of Mozilla at the end of 2000 Today in March of 2001 Mozilla s version is 0 8 According to Netscape the Mozilla code has been optimized and then stabilized before being called and distributed as the Netscape 6 product However when we tested some development possibilities as they are described on the Netscape developer web site we realized that some are not really possible with the current version 3 2 1 1 Blackwood API The Blackwood Project is a part of the Mozilla Project It deals with use of the Java language with Mozilla and Netscape The Java facilities of Netscape are based on the Open JVM integration facility which allows different Java e
14. example when the user wants to get a metadata record for a specific URL an order like this one is transmitted to the wrapper Message from Netscape Get metadata record http www google com And the wrapper will answer to Netscape giving it another simple string where tokens can be easily found by special character sequences like key and value Message to Netscape Metadata record http www google com key test1 value test1 key machine value super key truc value muchejuh key rtrytrytr value ngjv A great advantage of the fact that we have chosen the same wrapper is that it will be easier to integrate Netscape into the Construct environment Indeed there is only one wrapper for two applications and we can suppose that other extensions will be able to use it also TCP IP Emacs TCP IP Construct Metadata s Service A pe KA TCP IP Netscape 6 s Storage H bes v s s os ee a pa Emacs amp Netscape Wrapper Other Application I I I I I I I I L 15 4 2 Class diagram Connection 1 ResultTable NetscapeWrapper 4 2 1 NetscapeWrapper Class The NetscapeWrapper class is a simple class with the commands which can be sent to the server as final static parameters Here are the final static attributes which can be used when calling the NetscapeWrapper class instance GET _RECORD Get metadata record CREATE_RECORD Create metadata record
15. ication of the Construct metadata structural service component The sidebar interface on Netscape has been designed with the XUL language specially created in order to create the Netscape 6 user interface The metadata services interface is located in My Sidebar which is a frame located on the left side of the browser lt can be consulted at any time within all kinds of web pages This will allow ordinary WWW users to add metadata data about data to arbitrary documents on the WWW The JavaScript language combined with the LiveConnect technology permit communication between the XUL interface and the Java applet Users will also be able to access the metadata using a standalone Java application This program uses the same code as the Java applet but it has its own interface In a future version this application could be used with the XPCOM facilities to be linked to Netscape Both these solutions use the same wrapper as the Emacs integration with Construct Thus it will be easier to integrate all the applications in the Construct environment avoiding the multiplicity of wrappers The report continues with a short introduction to Construct that explains how this metadata project fits within the overall research project Section 2 Sections 3 and 4 provide details about the analysis and design of the Netscape 6 integration while Section 5 provides an overview of how to use the Construct metadata service in Netscape 6 and in the standalone meta
16. ish connection with a host which belong to the same domain that it is from The way to allow the applet to communicate with another host is to trust it e This can be by signing the applet so the operation can be transparent for the user who would like to use it e Another way is to install the applet on the user s local file system The applet must be placed in a CLASSPATH directory e The Java 2 security policy tool allows us to choose to trust applets from specific domains 4 Design 4 1 Description 4 1 1 Two applications in one The system can be seen as two different parts even though there is only one source code In fact the final code can be launched as an applet in an HTML or XUL page or as a standalone Java application 4 1 1 1 Applet The applet is launched as a normal applet it is called by a XUL or an HTML page between lt applet gt lt applet gt tags Therefore the applet has like others applets an init method which calls the jb nit method 4 1 1 2 Standalone application Because we have to load and run Netscape 6 each time we want to test the applet we have decided to make in parallel with the applet code a standalone application which permits us to test the main functionality This standalone application has its own swing Java interface Advantages of such a solution Having a standalone application in addition to the Java applet offers other advantages in addition to those for the development phas
17. lows the application to be used without any browser if you just have to consult documents metadata The standalone application which would communicate with the Netscape 6 application would probably be the best solution The fact that it would be a real application would let the user use it without the need to have to launch Netscape 6 to consult metadata He could consult them just by typing a URL in the application Use of XPCOM would enable future integration with the Microsoft Internet Explorer browser which uses the COM system to communicate with other applications Netscape 6 limitations and the Mozilla project There are many subprojects in Mozilla which should improve the Netscape Communicator browser The Blackwood Project is one of those subprojects of the Mozilla Project which is the open source development part of Netscape Some parts of the API are here but can be used only with very simple examples like some tests that are bundled with Mozilla source code Unfortunately the Netscape 6 browser cannot use the XPCOM capability which should be integrated in the next release of the product The problem is the same with the pluglet solution which can run but the API is not fully implemented and there are few possibilities today So for the project the last solution has been chosen the Java applet solution which is the only one which is not affected by Netscape 6 limitations 3 2 2 My Sidebar Description My Sidebar is a
18. mini wndow within Netscape 6 that can contain a Java applet or an HTML page It allows you to get the content of the web sites you choose It can also offer easy access to data from the web sites you want My Sidebar tabs can be constantly updated to keep you connected to the information you need My Sidebar tab is a web page formatted to fit in the My Sidebar window It supports languages like HTML 4 JavaScript XML CSS and DOM It allows tabs to be dynamic customizable and interactive Anything that can be done in a standard web page can be done in a Sidebar tab Therefore it is easy to integrate an interactive Java applet which could display metadata of the Netscape main frame Sidebar s advantages For developers it is easy to build update and manage the sidebar You can create the Sidebar tab like a web page and integrate a Java applet You can easily analyze the content of the web page in the main frame There is no need to modify the Netscape sources For web users it is convenient customizable and dynamic With My Sidebar tabs the web user can easily customize the metadata services applet It is very easy to install and use You just have to click on a link that runs a JavaScript function which installs the package needed on your computer Metadata are easily accessible at any time My Sidebar tabs can be updated automatically Tab content itself can be personalized to suit an individual s needs A user can interact with the tabs
19. ngines to be plugged in easily The advantages of this facility alone are obvious allowing users the freedom to choose whatever Java engine they want Pluglets or Java plugins Another possibility given by the Blackwood API is pluglets These are plugins and components that are implemented in Java giving the advantages of Microsoft s ActiveX controls while remaining cross platform A plugin is a code module that behaves as though it is part of the Netscape browser We can use the plugin API to create plugins that extend Navigator with interactive and multimedia capabilities that handle one or more data MIME types Generally plugins are developed in the C language and for the MS Windows platforms Plugins can use the Netscape Java Runtime Interface JRI to access Java Communication with Java and through Java with JavaScript is possible with a LiveConnect connection The Java plugin is useful when you have to use a singular data type It could be integrated to the web page XPCOM The Blackwood API would permit when it will be finished to connect standalone Java applications and Netscape using a COM like interface Netscape 6 should bring a COM compatible cross platform component object model called XPCOM It follows that Netscape components would be scriptable Component methods may be invoked from any language for which there exists a binding to the corresponding XPCOM interface In Netscape the primary language supported is JavaScript
20. ode read only only one query will be done Methods Core class methods can be divided into two parts e Internal methods these are private methods which are used to establish the connection and deal with the server e Interface methods these methods which are public are presented to the Interface instance and to the LiveConnect protocol Thanks to these methods LiveConnect is able to make the applet connected with the browser providing it queries data or document location for example 4 2 7 Communication between XUL and Java With Netscape it is possible to communicate between Java and JavaScript by using LiveConnect It is enabled by default in the browser For LiveConnect to work both Java and JavaScript must be enabled This protocol lets us perform the following tasks e Use JavaScript to access Java variables methods classes and packages directly e In JavaScript a wrapper is an object of the target language data type that encloses an object of the source language On the JavaScript side a wrapper object is used to access methods and fields of the Java object calling a method or accessing a property on the wrapper results in a call on the Java object When a JavaScript object is sent to Java the runtime engine creates a Java wrapper of type JSObject There are only two restrictions if you want to use a Java method the applet has to be loaded at the time of calling the Java method and this method must be public We use
21. re functionality which can be abstracted into a common package Generally a package is a Jar archive Add Tab to My Sidebar Add the tab www globesplorer corn to Mu Sidebar Source http into netscape cormihwdlaidusobxhttpc ane gloabexplorer com sidebarlsidebar htm A package can be added to an existing application without modifying it in any way It is also possible to use an installation procedure This kind of package is called an XP Installer package XPI A JavaScript function provides the ability to trigger it from a web page 19 5 User Manual The Construct metadata service functionality can be used in two different ways It can be launched in the Netscape 6 sidebar or run as a standalone application We shall see how to use these two interfaces which are quite similar 5 1 The Netscape 6 interface 5 1 1 Launch the metadata service The metadata services on the WWW have been included as a panel in the Netscape 6 My Sidebar To view the sidebar you have to select the My Sidebar item in the view menu Then it will appear on the left side of your browser N Netscape 6 VD My Sidebar bout blank v N If you want to run the Metadata service you just have to select the Metadata service item in the Tabs menu Then it will automatically display the application interface in the My Sidebar N Netscape 6 7 es oF E http goto ath cx v N My Sidebar Metadata service g ooo ooo T
22. rences Hostname localhost Port 16000 amy defaults no address no host 27 6 Conclusion The Netscape 6 metadata project has been a success The Construct metadata services are now available on the World Wide Web both as an integral part of Netscape 6 using an applet and as a standalone Java application The Netscape 6 integration software has been developed in a general way that will allow additional Construct structure services to be made available on the World Wide Web in the future using the general code base developed in this project 28 References 1 Blackwood Project API http mozilla org projects blackwood java util api index all html 2 JavaScript Developer Central http developer netscape com tech javascript 3 MySidebar s Developer s Guide http developer netscape com docs manuals browser sidebar index html creating 4 Netscape Plugins Developer s guide http developer netscape com docs manuals communicator plugin index htm 5 XUL Reference http www mozilla org xpfe xulref XUL_Reference html 6 XUL tutorial http www xultutorial com 7 Sun Java Reference http java sun com 8 JavaScript FAQ http developer irt org 9 Java developer connection http developer javasoft com 29
23. t to throw a security exception and exit An applet cannot load libraries or define native methods An applet cannot ordinarily read or write files on the host that is executing it An applet cannot make network connections except to the host that it came from An applet cannot start any program on the host that is executing it An applet cannot read certain system properties Java 1 1 introduced the concept of signed applets Signed applets allowed a user to verify the origin of the applet and its integrity This was done by digitally signing JAR files This model allowed the user to trust certain applets depending on whether they originated from a known trusted source Certain restrictions could be removed with this signing process However Java 1 1 provides only two levels of security safe or not safe Java 2 security policy The Java 2 security policy keeps the notion of trusted and un trusted code to a minimum Instead code runs at different permission levels This system improves the signed applet capabilities of Java 1 1 but this time a specific security level must also be supplied for a specific signed applet We can define for a specific applet files that it can read or write for example Construct Java applet and security In the Construct extension the applet needs to establish a connection with the metadata structure server This server could not have a web server to supply the Construct applet but the applet can only establ
24. tadata will be transmitted to this applet thanks to the LiveConnect protocol The second solution is the Swing interface of the Java applet This interface uses the most important part of the sidebar to display metadata We have discovered two problems with this solution It is not possible to use a Java applet in the sidebar so we have decided to create a frame in the sidebar in order to resolve this bug Unfortunately we cannot use a local applet for some security reasons that are why the applet is located on a distant web server The only data transmitted from the JavaScript to the applet is the URL of the current web page because metadata are directly fill and display via the Swing interface This kind of interface has been created for two reasons The applet could be run as a standalone application without Netscape 6 so a Swing interface is necessary It will be easier to integrate the applet to Internet Explorer if we want to make it an application of the Construct metadata structural service 3 2 3 Security issues Java applet security issues The original security policy of Java 1 0 uses the Sandbox model This model is very simple and restrictive The Sandbox represents a small part of the system resources the Java Virtual Machine JVM has access to Under this model applets were always assumed to be hostile so they were restricted to use Sandbox resources and nothing else Any attempt to leave the Sandbox would cause the apple
25. the isStandalone parameter will be set to false However if it is as a standalone application the parameter will be set to true through the main method Each method init or main will later call the jbinit method which contains the other instructions needed by the application 4 1 2 A wrapper Emacs wrapper A metadata extension has already been done for the Emacs software Due to the software implementation language Emacs metadata extension has been written in the Lisp language This extension provides the ability to consult metadata for documents which are opened in the text editor One Emacs buffer is used to edit the text and below it there is another buffer to display the metadata An entry in the main menu has been added to manipulate those data For communication between Emacs and the data server TCP IP has been chosen A wrapper in Java links the Emacs extension and the metadata server The Emacs extension sends via TCP IP queries to the wrapper which use Construct services to manipulate the data in the structure storage component Reuse of the wrapper We decided to keep the same wrapper to extend Netscape 6 In fact we have begun to test the first Netscape extension functionality with this wrapper Later we realized that this wrapper would be a good one for the Netscape extension project too It can manage the metadata with simple commands which are easy to understand and may be extended in the future For
26. tion services This category includes services such as concurrency control notification control and access control o Versioning services Services that allow structural abstractions to be versioned e Data stores A data store could be a file system a database a CD ROM etc e Infrastructure services This category includes general services that enable the individual components of the environment to co exist Examples of these services are service discovery naming and location e Development tools The development tools assist in the development of new services in the environment Currently three development tools exist o UML Tool This tool allows the developer to specify new services by drawing UML diagrams in a graphical user interface UML Tool translates the UML diagrams into IDL specifications o Emacs This well known editing tool is used to create IDL specifications and Java code as well as documentation of various kinds Emacs is considered a development tool of the Construct environment due to its integration with the navigational structure service o Construct Service Compiler CSC The CSC takes IDL specifications as input and generates service skeletons in Java Service skeletons are wrapped in components that can automatically run as part of the Construct environment The developer must add some code to the skeletons to define the semantics of the generated operations Development tools can also be clients of structur
27. va code should be usable with two types of interface a XUL one and a Java Swing one lf the user wants to use the standalone application the Swing interface will be used In applet use situations the XUL interface in the sidebar will be shown to the user The Swinginterface class contains all the attributes relating to the design of the interface lt implements also the methods necessary to handle the actions of the user on an element of the interface when he presses a button for example 4 2 5 ResultTable class The ResultTable class is an AbstractModelTable derived class which is used by the Interface class to display data in a scrollable table It has some methods which are called when core hash table has been altered 4 2 6 Core class The Core class is the central class the one which will join the interface part of the applet and the metadata server It will control the Connection class asking it to establish a connection at the beginning giving it a new server address or port The Core class will also instantiate the Connection and the Interface class Attributes After the first query to the server for a URL s metadata a hash table will be filled This hash table enhances performance because the client has the results in memory All the methods to consult the data will manipulate firstly the hash table After that if modifications have to be written on the server a query will be sent to it Therefore in a simple consultation m
28. ver you want to use You just need to enter the address and the port number of this server into the two corresponding fields It is also possible to restore the default parameters if you prefer to be connected to the default server J Goo gle Nets sC ape 6 R File Edit View Search Go Bookmarks Tasks Help T G Less http www google com wb Se http www google com N Geert e _ Google Search _ Enlarged Preferences Google Web Directo Server preferences the web organized by topic server adress a Advertise instantly With a credit card your ad goes on Google today port number 5 Cool Jobs Add Google to Your Site 16000 E ra 16000 Advertise with Us Google in your Language All About Google 62001 Google CR JOCUMEN 24 5 2 The standalone application If you do not need to consult any web pages you can run the Java applet as a standalone application The interface is quite similar as the Netscape 6 metadata service sidebar It still has three panels with the same functionality but there are also some differences 5 2 1 The Metadata panel First of all you have to enter the URL of the web page for which you want to consult the metadata When you have filled in the field press the update URL button Then the metadata and their values will appear as a list It is possible to select one or more keys by checking their Selected button and to delete them by pressing the delete button
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