1. Ptidej in my PaLM
Using explanations for
design patterns identification

2. Us
Æ Yann-Gaël Guéhéneuc
n 2nd year PhD student
n Object Models and Components Team
n Partly funded by Object Technology International, Inc.
(Canada)
Æ Narendra Jussien
n Assistant Professor
n Constraint Programming Team
Æ Research hosted by the
École des Mines de Nantes

3. Long-term goal
n Toimprove the quality of software
architecture
– To improve flexibility, understandability, …
– Maintenance = 75% of the life of a software
n Design patterns
« Describe simple and elegant solutions to specific
architectural problems in OO software design »
– Experience of skillful developers
– Recurrent architectural problems

4. sic Composite
A Ba xample :
E pattern solution
Composite composes objects into tree structures to
represent part-whole hierarchies. It lets clients treat
individual objects and compositions of objects uniformly.

5. Main ideas
n Design patterns are good micro-
architectural solutions
n Micro-architectures
close to a design
pattern solution may be improved
n Theseare transformed into the
corresponding design pattern solution

6. Problem
n To identify
– The Use of a design pattern solution
• Well written code
• Notion of complete version
– The Misuse of a design pattern solution
• Code improvement
• Notion of distorted version
+ No up-front descriptions of the distortions

7. ic
A Bas xample : Problem
E
Complete and
distorted versions?

8. Complete and distorted versions
n Related works
– The search of sub-graphs in a graph
– The phase of adaptation in case-based
reasoning
n But we need complete and distorted
versions
Æ Explanation-based CP (eCP)

9. Solution
n Explanation-based CP enables
– Justifications
• Programming = « artistic » activity
• Explain why / how the code is modified
– Complete and distorted versions
– Strong interactivity with the user
• Dynamic description of the distortions

10. Explanation-based CP 1/3
n Setof constraints justifying an
action performed by the solver
– Value removal
– Contradiction
n Trace of the solver behavior

11. Explanation-based CP 2/3
n Application
– Assistance upon failure
– Interactive solvers
– New search algorithms
• Path-repair (AAAI 2000)
• Mac-DBT (CP 2000)
•…

12. Explanation-based CP 3/3
n An implementation: PaLM
– Developed at the EMN
– On top of Choco
– Written in Claire
– Used in Path-Repair, Mac-DBT
– Reliable and efficient

13. Our application
n The design pattern solution
– A class defines a variable
– Relationships among classes define
constraints
n The source code of the application
– The classes define the domain of the
variables
– Relationships among classes give the
semantics of the constraints

14. ic
A Bas xample : Constraints
E
n The Composite design pattern solution
n Its constraints
composite < component
leaf < component
composite ⊃ component

15. ic
A Bas xample : Interaction
E
composite < component
leaf < component
composite ⊃ component

16. ic
A Bas xample : Results
E

17. Our results 1/3
n Implementation
– Constraints
• Inheritance, creation, composition, …
– Design pattern solutions
• Composite, Façade, Factory Method, …
n Experiments
– Small test-cases
– JEdit v3.1 (~250 classes), JHotDraw v5.1
(~155 classes), Ptidej itself (!), …

18. Our results 2/3

19. Our results 3/3

20. Conclusion and future
n An application of explanation-based CP
– Non-trivial problem
n Short term
– To add more design pattern solutions
– To develop the constraints system
• New algorithm CSP-NN [Morning session]
– Scalability and weights (noise)
n Long term
– automation and interaction (usability)