Software ReCreation

1
Software Re-Creation

• From Legacy to Component
• Arie van Deursen

2
Software Duplication

• Programs
• Dit programma is grotendeels een kopie van het
  XY progamma ABCD123.
• Subsystems
• CICS and BATCH functionality
• Functions Computations
• Entire systems

3
Function Duplication Example

• When is a year a leap year ?
• Two (small) 100.000 LOC systems contained 8
  different computations!

IF YY 92 OR 96 MOVE 29 TO MD(2) END-IF
4
Component Software

• Technology
• Abstraction
• Selection
• Specialization
• Integration

• Process
• Create reusable assets
• Support
• Reuse
• Manage

AND ONLY ONCE!
Kent Beck Say it once!
5
Financial Products

• Loan, swap, future, FRA,
• Introduce innovative products
• Banks backoffice hard to adapt

• Describe products at high level
• Generate (COBOL) code
• At MeesPierson, with CAP Gemini

6
Domain-Specific Languages
Product Specification
7
Domain Engineering

• Identify potential reusable assets
• Domain family of systems
• 3 legacy 3 future
• Economy of scope
• Organizational learning

Domain Engineering
8
Organizational Domain Modeling (ODM)

• Plan Domain
• stakeholders
• domain boundary decisions
• examples
• counter-examples

• Model Domain
• domain experts
• reverse engineer legacy systems
• lexicon of terms
• commonality
• variability

• Engineer
• Asset Base
• scope
• architect
• implement

9
Reverse Engineering Tools
Legacy Sources
10
Large classes
Small classes
11
Summary

• Components
• Abstraction
• Selection
• Specialization
• Integration

• Domain Engineering
• Comonality
• Variability
• Economy of Scope
• Family of systems

• Domain-Specific Languages
• Program Understanding Tools

12
In Conclusion
CBD essential for producing quality software

• Recommended Reading
• Meyer Object-Oriented Software Construction
• Brooks The Mythical Man Month
• Jacobson, et. al. Software Reuse

• Quote from Alan Kay
• To be a good software engineer,
• you need the ability to feel pain

13

• Questions?

14
Component-Based Development Keywords

• Object-Oriented Application Framework
• Hot Spots
• Design Pattern
• Java
• Object Request Brokers, CORBA, DCOM
• Software Architecture
• Unified Modeling Language
• N-Tier Systems