Reengineering Patterns

1
Reengineering Patterns

• http//www.iam.unibe.ch/famoos/
• Serge Demeyer
• Stephane Ducasse
• Oscar Nierstrasz

2
Reengineering patterns

• First Contact
• Read all the code in one hour
• Skim the documentation
• Interview during demo
• Initial Understanding
• Detailed Model Capture
• Prepare Rengineering

3

• First Contact
• Initial Understanding
• Speculate about domain objects
• Reconstruct persistent data
• Identify the largest
• Recover the refactorings
• Detailed Model Capture
• Prepare Rengineering

4

• First Contact
• Initial Understanding
• Detailed Model Capture
• Derive public interface
• Step through execution
• Prepare Rengineering
• Refactor to understand

5
Risks

• Limited resources
• Tools and techniques
• Reliable information
• Accurate abstraction
• Skeptical colleagues

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Read all the code in an hour

• Time box
• Afterwards, spend an hour to write up
• important entities
• techniques or styles used
• potential problems

7
Skim the documentation

• Produce short report
• Check dates - is it out of date?
• Table of contents, design overview

8
Interview during demo

• Document
• key usage scenarios
• main features and whether users like them
• system components and responsibilities
• interesting stories you hear
• Interview a variety of people

9
Speculate about domain model

• Make a domain model (class diagram, etc)
• Check it against source code
• Keep track of names that do not match concepts
• Alternative extract design with tool and then
  compress it

10
Reconstruct persistent data

• Persistent data is usually most important
• Examine the data itself, not just class diagrams
  or schema
• Develop model of data (class diagrams or schema)

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Identify the largest

• Largest
• class hierarchy
• class
• method
• Largest is often
• the most important
• the biggest problem

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Recovering refactorings

• Look at successive releases of the system
• Look for major design changes, major
  simplifications
• Figure out why they were made

13
Derive public interface

• Which classes are public?
• Which methods are public?
• Language features for private/public
• Cross reference

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Step through execution

• Requires good programming environment
• Document flow of control (but abstract!)
• Build dynamic model

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Prepare for reengineering

• Refactor to understand
• Write the tests
• Prepare a prototype

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Homework

• Read http//www.iam.unibe.ch/ famoos/Deme99n/ or
  http//www.iam.unibe.ch/famoos/
  patterns/rvPatt08.pdf
• Select one of the five forces or risks.
• You may talk about this homework with up to two
  other people, but they may NOT have selected the
  same risk as you have.

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• Write two or three pages to answer the following
  questions.
• How do the patterns address your chosen risk?
  Write at least a page on this.
• What did the paper miss about your risk? It
  might miss how one of the patterns addresses the
  risk, or it might miss a pattern that could be
  used to address the risk. If you cant think of
  anything, pick a different risk!