Improved Traversal Techniques with Demeter-Style Visitors in AIP

1. Proposed Ideas Therapon Skotiniotis Karl Lieberherr Northeastern University Boston, MA 02115 USA ABB Workshop

2. Traversal Related Concerns • AIP performs lookups on hierarchical structures • NamePaths, Aspect Directory etc • Demeter Theories could be deployed (XPath) • User friendly specification of Paths from GUI via Valve to ValveTemperacture from GraphicDisplay to * • Adaptable specification • Ability to add behavior on a group or substructure through the introduction of Demeter Style Visitors ABB Workshop

3. Traversal Related Concerns(cont) • Demeter Style Visitors • Perform operations before/after/around a specific node that is being visited • Encapsulates behavior in a separate file • Easier extensibility • Potential operations • Maintenance of Structures • Recording of dependencies • Type Level ASK • Instance Level ASK • Copying of structures • Ready made global operations on structures ABB Workshop

4. Traversal Related Concerns(cont) Room A/C Valve getRTemp getTemp ABB Workshop

5. Traversal Related Concerns(cont) Room_climate_comp Valve_temp_comp Room A/C Valve getRTemp getTemp Traversal + Visitor: from Room to getTemp(VmakeComponent) Traversal + Visitor: from Room to getRTemp(VmakeComponent) ABB Workshop

6. AOSD already in AIP • “The house that ABB build” • Trackers and Hooks • The ideas are really close to • JoinPoint model • Hooks are a restricted pointcut for creation, modification and alteration • Trackers are a bit more flexible • You can define the AIP aspects upon which you can capture • Creation, Deletion, Setters, Notifications ABB Workshop

7. AOSD already in AIP (cont) • Adding • Method invocations will give a similar JoinPoint model as that of AspectJ. • Can be accomplished • Using a language specific approach ala AspectJ • Introduce a “Intermediary” component to delegate according to the pointcuts provided by the programmer • Through a design constraint enforced by an API (yet another one) • Issues • Language specific • Harder to implement • Programmers need to learn a new sub-language ABB Workshop

8. AOSD already in AIP (cont) • Issues (cont) • Intermediary component • A new tool rewrites the programmer’s source (preprocessor) making all necessary arrangements. • Compile time + Runtime performance issues. • Automatically tangle code  harder to provide runtime adaptability • Programmer can be oblivious to the whole mechanism • Just uses the extra facility if he needs to. • Design Constraints via an API • Extra components introduced at Framework level (might affect stability and/or performance) • Maintain runtime adaptability. • May become too verbose for the programmer ABB Workshop

9. Reuse Reuse Reuse • Fine grained separation + subjective view make reuse between systems difficult • Duplicated information • Dependencies between views • Underlying implementation • Context sensitive dependencies • HyperJ Solution • HyperSpaces and Multi Dimensional Separation of Concerns • Binary manipulation. No need of source code • Language specific (if at all possible) ABB Workshop

10. Component Based Reuse • The ability to reuse “building blocks” to provide • Similar solutions to similar problems • Create a new solution by adopting multiple collaborations together and then applying them to the underlying system • Capture parts of the systems structure that are paramount to the solution • Define what abstract component types are expected/provided only • This requires a coordination between • Structural Dependencies within Structures (Directories in AIP) • Behavioral Dependencies between entities (DLL’s ASO’s etc) ABB Workshop

11. Component Based Reuse (cont) • Structural Dependencies • XPath and a default visitor could capture structural dependencies • Trackers and Hooks can be deployed by the programmer to capture behavioral dependencies ABB Workshop

12. Traversal Related Concerns(cont) • XPath • Follows the same idea • Allows also for documenting AIP structures to * (MakeHMTLVisitor) • “Write once runs on any Structure” ABB Workshop