A Discussion of: Murphy, Notkin & Sullivan ’s Software Reflexion Models: Bridging the Gap between Source and Hi

1. André M. Carrington for CS 846 October 2011. v1.01. David R. Cheriton School of Computer Science University of Waterloo A Discussion of:Murphy, Notkin & Sullivan’sSoftware Reflexion Models: Bridging the Gap between Source and High-Level Models

2. Agenda • Context • The Reflexion method • Contributions claimed, impact award • Motives, applications & extensions • Demo Note on Reflexion: The old English spelling differentiates [their] use of “reflexion” from the field of reflective computing [Smi84]

3. In the last two classes we covered papers on • Information needs • analysis • synthesis (of fragments) • Code search, for • reuse • debugging, understanding

4. Some points that we discussed are relevant to this paper: • Accurate system information is important • Documentation is often inaccurate • What provides the information sought? • Developers may be under pressure

5. A Typical Scenario* *from G.C. Murphy’s presentation: Structural Summarization, 1996. This example is also discussed in the paper re: a developer with expertise in UNIX virtual memory but not NetBSD as a specific implementation.

6. Context circa 1995 *from G.C. Murphy’s doctoral dissertation (on the same topic as the paper), 1996.

7. Reflexion bridges the gap between source and models 4 1 3 2

8. 1. Alice creates a High Level Model

9. 2. Alice extracts a Source model • She uses FIELD’s xrefdb* and an awk script to obtain “calls relation” tuples: calling fn called fn *XREFDB is a relational database whose relations were specifically designed to support queries about programming languages. FIELD is a distributed programming environment/solution.

10. 3. Alice maps the HLM to Source • Using general domain knowledge, specific codebase knowledge, or assumptions. • Source entities* are grouped or abstracted using regular expressions, directories, files, classes and functions/methods. • A partial map re scope (subsystems) of interest is allowed. *from the calls relation, from browsing, or from knowledge or other sources Source High-Level Model (HLM)

11. 4. Alice computes a Reflexion Model

12. Alice may iterate by refining the HLM & Map from the Reflexion 4 1 3 2

13. How does it work? Want proof?Learn static code in Z…

14. And computations in Z, or…

15. Read the source. Try it. Read the thesis. Apply it to itself! • An Eclipse plugin for Java (built from source) is available at: • http://sourceforge.net/projects/jrmtool/ • One of the web pages said to e-mail Professor Gail Murphy for other versions (e.g. standalone, other languages).

16. Metrics are provided to demonstrate its viability.

17. Contributions claimed • Reflexion “enables an engineer to produce sufficiently accurate high-level models in a different way”. • Reflexion “has been applied to aid engineers in performing a variety of software engineering tasks on a number of different software systems that vary in size and implementation language” • Reflexion “permit[s] an engineer to easily explore structural aspects of a large software system” • A benefit of the paper’s “syntactic approach is the ability…to investigatemany different kinds of structural interactions in a software system (calls, data dependencies, or event interactions, etc.).

18. Contributions claimed • “The declarative maps…enable an engineer to focus on information of interest” • Reflexion models “bridge the gap between an engineer’s high-level model and a model of the source” • Lastly, they almost suggest their goal was met: • “The goal…to produce, at low cost, high-level models that are ‘good enough’…Three aspects…critical to meeting this goal are the use of syntactic models, the use of expressive declarative maps, and support for querying a reflexion model.”

19. Impact Award • ACM’s Special Interest Group on Software Engineering – SIGSOFT – launched an initiative several years ago to recognize research papers that have been particularly influential in software engineering research.  • This 1995 paper on Reflexion models was selected to receive a 2011 SIGSOFT Retrospective Impact Paper award. • Citations: 422 (Google); 93 (ACM digital library) • The most ideal impact, in my view, would be: widespread use in industry.

20. Motivation • I select papers: • that provide value to society; and • that are interesting or inspiring. • This paper extended my thinking about what is possible. • I think that many people would use the Reflexion tool if it were marketed (and if the paper was more accessible to a non-academic audience).

21. Applications of this Research • Reengineering • Getting acquainted with a codebase to re-engineer a VM • Understanding & assessing structure to re-engineer Excel • Conformance • Assessing conformance to layered architecture, directly. • Assessing conformance to design documentation • System Understanding • Getting acquainted with a codebase in general • Seeing how others’ work combines & aligns with your own • Observing meaningful divergences, e.g. between a difficult-to-understand compiler and a typical compiler) • Finding optimizations in divergences, e.g. VM

22. Challenges • The RMTool download link does not work. • The link to the no-install plugin approach for the jRMTool does not work. • The jRMTool requires fixes (which I achieved) to get it working on a current version of Eclipse, because of • a deprecated method (requiring changes to code); and • deprecated code practices (requiring use of an older java compiler version and disregard for warnings) • The sourceforge project does not have any recent activity; and thus support for the tool is in question.

23. Research Extensions • A better survey (and objective measure) of sufficiency and utility – with a statistically significant sample size. • While the Related Work section appears to be well written, a presentation by the authors of FIELD* at around the same time (1993) that provides a taxonomy of development tools for visualizing abstractions, that might better contextualize and advance this work. • They indicate: • Support for typing relations in source models and HLMs • Examine the sensitivity of the Map to changes in source • Improve querying to assist interpretation of Reflexion models *FIELD’s xrefdb is used by the paper for source model extraction

24. Reiss’ Taxonomy • Syntactic: • Call graph • Class hierarchy display • Design language • Semantic: • program slices • data flow graphs • library-based (e.g. threads) • potential class groupings • Event: • dynamic call graph • synchronization viewer • algorithm animation • Data-based: • data structure visualization • make dependency graph Reiss, Stephen P. “FIELD: Friendly, Integrated Environment for Learning and Development” (presentation), Brown University, 1993.

25. Demo with a simple program

26. Demo with a simple program

27. Demo with more complexity

28. This concludes the presentation.

29. Trivia with prizes!(or obscure things I learned) The first to correctly answer wins a prize! • What formal specification language is used in the paper? Answer: Z • What does the K in AWK stand for? (hint: they co-authored a book on C) Answer: Kernighan (1st reference) • What late pop star is mentioned in the paper? Answer: Michael Jackson (Acknowledgements)

30. Lexical Source Model Extraction* *from G.C. Murphy’s doctoral dissertation (on the same topic as the paper), 1996.

31. LSME Detail *from G.C. Murphy’s doctoral dissertation (on the same topic as the paper), 1996.