Reverse Engineering and Design RecoveryInformatics 122

Alex Baker

Definitions Reverse Engineering: Analyzing a system to:

1. Identify its components and their relationships

2. Create representations in another form Usually refers to redocumentation

Design Recovery A subset of reverse engineering A higher level understanding

(Chikofsky and Cross, 1990)

Also like a double-waterfall…

General model for recovery (Byrne, 1992)

Existing System Target System

Implementation

Design

Requirements Requirements

Con-ceptual

Con-ceptual

Design

Implementation

re-think

re-specify

re-design

re-build

Alteration

ReverseEngineeringAbstraction

ForwardEngineeringRefinement

What is the Design?

The basicsBeast and Superbeast classesAI classesData structureEngine structure

What is the Design?

We want a game based on Beast We want it to be expandable We must be able to add more monsters To enact this we want to use interfaces A lot of this is enacted through pushable Pushable is used by the engine to…

What if we want to…

Change the double-beast-push behavior

Add a new monster type

Let the player climb on top of blocks

Simplify the design

What is the Design?

The basicsBeast and Superbeast classesAI classesData structureEngine structure

What is the Design?

We want a game based on Beast We want it to be expandable We must be able to add more monsters To enact this we want to use interfaces A lot of this is enacted through pushable Pushable is used by the engine to…

What do we use?

Reverse engineering recreates design abstractions from Code Existing design documentation (if available)

Personal experience / general knowledge about problem and application domains

Talking to people

(Biggerstaff, 1989)

What do we Create? Recovered abstractions need:

Formal specifications Module breakdowns Data abstractions Dataflows Informal knowledge

All information required to understand What How Why

(Biggerstaff, 1989)

Why do we have to do this?

Why do we have to do this? Working with others’ code…

Debugging

Maintenance Modification Reuse

Working with your own code

You will work with code in the absence of a design

Motivation: No design

Lost design Build-and-fixed Agile methodologies

Incomprehensible design

Motivation: Design Drift

Motivation: Design Drift

Design not followed

Motivation: Design Drift

Design deviations

Motivation: Design Drift

Design deviations

Motivation: Design Drift

Design deviations

?

Motivation: Design Drift

Design deviations

???

Motivation: Design Drift

Design deviations

???

???

Motivation: Design Drift

Design deviations

???

???

Motivation: Design Drift

Design deviations

???

???

Motivation: Design Drift

Design deviations

???

Motivation: Design Drift

You’re often recovering, in some sense

Deviations happen

Sometimes you’re formally making a spec

Sometimes you’re just trying to figure out what the heck someone was thinking…

What are the Goals of RE

Cope with complexity Generate alternate views Recover lost information

Detect side effects Synthesize higher abstractions Facilitate Reuse

(Chikofsky and Cross, 1990)

What are the Goals of RE

Cope with complexity Generate alternate views Recover lost information

Detect side effects Synthesize higher abstractions Facilitate Reuse

Redocumentation

Design Recovery

All this code

What does it mean?

So lets start with the basics

Recreating the structure (redocumentation)

Existing System Target System

Implementation

Design

Requirements Requirements

Con-ceptual

Con-ceptual

Design

Implementation

re-think

re-specify

re-design

re-build

Alteration

ReverseEngineeringAbstraction

ForwardEngineeringRefinement

Object Orientation

Something of an advantageClass names, function namesEstablished relationships (inheritance,

members, etc.)

Cohesion

The Ideal Program (again)

…

vs.

Finding the structure

Entities Classes Methods Variables

Relationships Inheritance Member Objects Method calls

Approaches

Reverse engineering toolsE.g. Omondo

Reading documentation Reading class names Code reading Talking to people

Also, remember

Existing artifacts, but also Personal experience General knowledge about problem General knowledge about solution

goals

In terms of our process model

them

Ideas (languages) representations (languages)

you

Ideas (languages)

if(condition) functionCall(X);else functionCall(Y);

goals

knowledge

knowledge

An example: Jetris

http://jetris.sourceforge.net/

Reverse Engineering Jetris

Multiple “passes”Run the gameReading namesWhat is HTMLLink? PublishHiScore?What is Figures.java? FigureFactory?TetrisGrid (wait, what’s with those arrays?)AddFigure, dropNext, addFigureToGrid…Actual loop? (nextMove)UI

Goals and Knowledge

Of Tetris

Based on other artifacts (running program)

Of tendencies?

Patterns?

Lets get philosophical again!

Design Recovery in our Models

Feasible Desirable

Conceivable

Outcome Space

Design Space

Design Recovery (Product)

Feasible Desirable

Conceivable

Outcome Space

Design Space

Design Recovery (Product)

Feasible Desirable

Conceivable

Outcome Space

Design Space

Design Recovery (Product)

Feasible Desirable

Conceivable

Outcome Space

Design Space

Not Just the UML

What principles were applied?What were their priorities?What patterns emerged?What actual patterns were used?

What would developers making changes need to consider?

This will save you a lot of trouble

Another (Small) Example

addAllPixels(Image image){

for(int i = 0; i < image.getWidth(); i++){

for(int j = 0; j < image.getHeight(); j++){

Color c = image.getColor(i, j);

addPixel(new Pixel(i, j, c));

addToColumn(i, new Pixel(i, j, c));

updateColorTotals(c);

}}}

We might be able to guess that:

Need for a pixel class Different instances for

addPixeladdToColumn

Concerned about speedNot so much about space

Concerned about changability?Or just following convention

Could have just been

addAllValues(ImageNumber n){

for(int i = 0; i < image.height; i++){

for(int j = 0; j < image.height; j++){

colorArray[n][i][j] = image.colorAt(i, j);

}}}

The other side of the coin…

How easy is your program to understand?The dual nature of code

How is your: Documentation Naming Code Metaphor Principles

Finally: What’s Actually Created?

It depends: How difficult? Who else? The future…

Getting philosophical one last time

Design Recovery (Process)

activities

Ideas (languages)

activities

Ideas (languages)

representations (languages)

if(condition) functionCall(X);else functionCall(Y);

Design Recovery (Process)

activities

Ideas (languages) representations (languages)

activities

Ideas (languages)

representations (languages)

if(condition) functionCall(X);else functionCall(Y);

Design Recovery (Process)

activities

Ideas (languages) representations (languages)

activities

Ideas (languages)

representations (languages)

if(condition) functionCall(X);else functionCall(Y);

goals

knowledge

Finally: What’s Actually Created?

It depends: How difficult? Who else? The future…

We could make UML UI map Program flow Description/Depiction of array metaphors …

Assignment 3 – Design Recovery

Recover the design of PalantírTool for awareness in configuration

management systems developed at UCIYou may use any tools you likeDo not ask anyone about it (despite that

normally being a good resource)

Get the Palantír code from the subversion repository, detailed instructions follow

Assignment 3 – Design Recovery Each group must turn in:

A Complete* UML (-ish) Diagram At least 1 additional diagram of your choice (might be informal) A document describing the design of Palantír (at least 4 pages)

Your audience is someone unfamiliar with Palantír who needs to make very significant changes to it

The code may no longer compile! Your submission graded on completeness, clarity, accuracy

Each person also needs to submit a team evaluation (forms available on class webpage)

Paper copy due Monday, February 9th, at start of class

* see next slide

Assignment 3 – A Caveat on “Complete”

Concentrate on (give complete design of) four packages: edu.isr.palantir edu.isr.palantir.core edu.isr.palantir.server edu.isr.palantir.ui

Other packages and libraries are in the repository! (12) They will be useful references in recovering the design. You must check them out and use them in your analysis. You do not need to fully recover their internal structure. Represent them as amorphous blocks in your UML. Be sure to show, e.g., calls that are made to them, from the four

main packages.

Suggestions for Group Work

Everyone start by taking their own look at the whole systemMultiple perspectives will be very useful

Work out the high level architecture Concentrate on the four main packages Understand program flows Look out for subtle details

Further tips

There are papers available on Palantír on André's website; feel free to consult them

Use representations of classes to organize

Rote completeness is not the answer, will need to be elegant

Team AssignmentsTeam 1 Tomas Ruiz-Lopez Lance Cacho Daniel Morgan Scott Ditch Joshua Villamarzo Derek Lee

Team 2 Alton Chislom Jeffrey Gaskill Matt Fritz James Rose Robert Duncan

Team 3 David Schramm Leslie Liu Chad Curtis Alex Kaiser Ben Kahn

Team 4 Jay Bacuetes Robert Jolly James Milewski Lance Zepeda Aylwin Villanueva

Team 5 Alexander Doan Jordan Sinclair Rakesh Rajput Matt Shigekawa Scott Roeder

Detailed Checkout Instructions

Two Steps:

1) Install Subclipse plugin for Eclipse

2) Check out the Palantír repository

NB: this assumes that you're using Eclipse and are otherwise comfortable with it.

Detailed Checkout Instructions1. In Eclipse, go to Help > Software Updates > “Available Software” tab

Detailed Checkout Instructions2. Hit “add site”, enter location: http://subclipse.tigris.org/update_1.4.x

Detailed Checkout Instructions3. Hit “OK” => Check the Subclipse main box => hit “Install”

Detailed Checkout Instructions4. Make sure everything is checked off and hit “Finish”

Detailed Checkout Instructions5. Let the libraries download => hit “Yes” at this dialogue box

Detailed Checkout Instructions6. Make a new Project (NOT Java Project) and choose this

Detailed Checkout Instructions7. Make a new repository location

Detailed Checkout Instructions8. Enter http://tps.ics.uci.edu/svn/projects/palantir/trunk/ and hit “next”

Detailed Checkout Instructions9. Select the root of the tree => hit “Next” (NOT “Finish”)

Detailed Checkout Instructions10. Check out in the workspace => give it a name => hit “Finish”