ICEIS 2007 Special Session 3 - Computer Supported Collaborative Editing Ansgar R.S.Gerlicher

1. TRANSPARENT EXTENSION OF SINGLE-USER APPLICATIONS TO MULTI-USER REAL-TIME COLLABORATIVE SYSTEMSAn Aspect Oriented Approach to Framework Integration ICEIS 2007 Special Session 3 - Computer Supported Collaborative Editing Ansgar R.S.Gerlicher gerlicher@hdm-stuttgart.de

2. Content • Introduction • Aspect Oriented Programming • The Application and the Framework used • Integration Steps • Conclusions • Demonstration Video ICEIS2007 - Ansgar Gerlicher

3. Introduction The Challenge • Extend an existing single-user application with collaborative functionality • without changing the applications source code (transparent extension) and • with as little effort as possible The Approach • Concentrate on the data model manipulation concerns • and use aspect-oriented programming • to integrate a collaboration framework ICEIS2007 - Ansgar Gerlicher

4. Aspect Oriented Programming (AOP) • A programming paradigm originated by Gregor Kiczales et al. at Xerox PARC, 1997* • Attempts to aid programmers in the separation of concerns, specifically crosscutting concerns • Aspects can alter the behavior of the base code by applying advices • Advices define additional behaviour at join points • Join points are specified by using a quantification or query called a pointcut • AOP extensions for many programming languages exist. AspectJ is the most popular AOP extension for the Java programming language * Kiczales, G.,et al. Aspect-Oriented Programming.In Proc. of ECOOP 1997, Springer-Verlag LNCS 1241. June 1997. ICEIS2007 - Ansgar Gerlicher

5. The Application and the Framework used GLIPS Graffiti SVG graphics editing application • Open source graphics editor developed by ITRIS • Java based • Supports editing of SVG graphic documents • Uses the W3C DOM API internally for manipulation of the SVG documents Collaborative Editing Framework for XML (CEFX) • Real-Time collaboration on XML documents • Optional locking of nodes • Awareness support • Flexible plug-in architecture ICEIS2007 - Ansgar Gerlicher

6. The Collaborative Editing Framework for XML (CEFX) CEFX Architecture Overview Other components Other components ICEIS2007 - Ansgar Gerlicher

7. Integration Steps • 1. Identify the crosscutting concerns of data model manipulation of the single-user application (GLIPS uses the DOM API) • 2. Specify join points for the relevant calls to the data model manipulation API (DOM API) • 3. Define advices for delegating corresponding actions to the collaborative editing framework ICEIS2007 - Ansgar Gerlicher

8. Call Interception Integrating CEFX into GLIPS using AOP Element CEFXDOMAdapter CEFXController Single-UserApplication Advice setAttribute setAttribute(name:String,value:String) setAttribute(target:Element,name:String,value:String) Element_setAttribute(target:Element,name:String,value:String) Operation= createUpdateOperation(...) executeOperation(op:Operation) JoinPoint: call(void setAttribute(String,String)...) Call interception, delegation to Advice: void around(Element p, String attr, String value) ICEIS2007 - Ansgar Gerlicher

9. Conclusion Pros • Little programming effort: only seven advices where needed • No source-code modification necessary • Application-transparent • Reusable advices • Acceptable performance Cons • Still some AOP implementations require source code recompilation • AOP is still an immature technology, resulting in lack of tool support and adoption risks ICEIS2007 - Ansgar Gerlicher

10. Collaborative Editing Demonstration ICEIS2007 - Ansgar Gerlicher

11. Thank youfor your attention ICEIS 2007 Ansgar R.S.Gerlicher gerlicher@hdm-stuttgart.de Stuttgart Media University (HdM) and London College of Communication