A Discussion of:

Murphy, Notkin & Sullivan’sSoftware Reflexion Models: Bridging the Gap between

Source and High-Level Models

André M. Carrington for CS 846 October 2011. v1.01.

David R. Cheriton School of Computer ScienceUniversity of Waterloo

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AgendaContext

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]

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In the last two classes we covered papers on

Information needsanalysissynthesis (of fragments)

Code search, forreusedebugging, understanding

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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

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A Typical Scenario*

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

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Context circa 1995

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

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Reflexion bridges the gap between source and

models

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1. Alice creates a High Level Model

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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.

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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

3. Alice maps the HLM to Source

Source High-Level Model (HLM)

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4. Alice computes a Reflexion Model

Src HLM

✔ ✔

✔ ✖

✖ ✔

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Alice may iterate by refining the HLM & Map from the

Reflexion

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How does it work? Want proof?Learn static code in

Z…

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And computations in Z, or…

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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).

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Metrics are provided to demonstrate its viability.

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Contributions claimedReflexion “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 investigate many different kinds of structural interactions in a software system (calls, data dependencies, or event interactions, etc.).

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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.”

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Impact AwardACM’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.

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MotivationI 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).

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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

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ChallengesThe 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 ofa 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.

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Research ExtensionsA 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

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Reiss’ TaxonomySyntactic:

Call graphClass hierarchy displayDesign language

Semantic:program slicesdata flow graphs library-based (e.g.

threads)potential class groupings

Event:dynamic call graph synchronization vieweralgorithm animation

Data-based:data structure

visualizationmake dependency graph

Reiss, Stephen P. “FIELD: Friendly, Integrated Environment forLearning and Development” (presentation), Brown University, 1993.

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Demo with a simple program

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Demo with a simple program

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Demo with more complexity

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This concludes the presentation.

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Trivia with prizes!(or obscure things I learned)The first to correctly answer wins a prize!

1. What formal specification language is used in the paper?

Answer: Z

2. What does the K in AWK stand for? (hint: they co-authored a book on C) Answer: Kernighan (1st reference)

3. What late pop star is mentioned in the paper?

Answer: Michael Jackson (Acknowledgements)

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Lexical Source Model Extraction*

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

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LSME Detail

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