1. 1 Increasing the Confidence of Engineers during Component Upgrades Marija Rakic marija@sunset.usc.edu ARR, February 6 th, 2001

2. 2 Outline Motivation Approach Implementation Future work

3. 3 Motivation Incorporating into a system a new version of already existing component (component upgrade) Is the desired functionality from the old version correctly preserved? Are there new errors introduced with the new version? Is there any performance discrepancy?

4. 4 Possible Outcome Replace the old version with the new version Retain the old version e.g., in case the new version introduces too many problems Maintain multiple versions of a single component in the system

5. 5 Approach Software Architecture Separation of data and processing elements (components) from interaction elements (connectors) Multi-Versioned connectors (MVC) Component: WordCounter Operations: countWords(text):int; countSentences(text):int; countLines(text, pageWidth):int

6. 6 Canvas MVC Word Counter version 1 Word Counter version 2 Word Counter version 3 M N N N N N N N N N N

7. 7 Role of MVC Responsible for hiding from the rest of the system the fact that a given component is multi-versioned Relaying invocations and propagating result(s) Allows specification of component authority for different operations Authoritative – nominally correct w.r.t. a given operation Logs results and compares them to the authoritative version’s results

8. 8 Dynamism in MVC Changing component authority at runtime Inserting and removing new versions at runtime Accomplishing desired functionality Using multiple components that provide complementary functionality together Logging execution history in order to undo runtime changes to an application

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10. 10 Future work Comparisons of results Currently relies on similarity of versions Existence of equal method Combination of results, states, and message patterns Non-terminal operations Automated decision-making Measurements of overhead execution speed application size

11. 11 References Marija Rakic and Nenad Medvidovic. Increasing the Confidence in Off-the-Shelf Components: A Software Connector-Based Approach. To appear in Proceedings of the 2001 Symposium on Software Reusability (SSR'01), Toronto, Canada, May 18-20, 2001.