1. ADAPTIVE PROGRAMMING
Sezen ERDEM
December 2005

2. Outline What is Adaptive Programming? Law of Demeter
Structure-Shy Behavior (Traversal Strategy)
Propagation Patterns
Example
Development Tools
Conclusion
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Adaptive Programming

3. What is Adaptive Programming?
Changes its behavior according to its environment
Encapsulates class hierarchies using traversal strategies and visitors
An extension of OOP using graph theory and formal languages to further abstract collaborating classes and generate a family of programs from a common architectural graph.
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Adaptive Programming

4. What is Adaptive Programming?
Aspects or components use graphs which are described by traversal strategies.
A traversal strategy defines traversals of graphs without referring to the details.
Adaptive programming is aspect-oriented programming with traversal strategies.
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Adaptive Programming

5. What is Adaptive Programming?
Adapts automatically to changing context
Class structures are described partially
Behavior is not implemented exhaustively
Methods are implemented when they are needed
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Adaptive Programming

6. History
1982: Hades (Hardware DEScription language by Niklaus Wirth at ETH Zurich)
: Zeus (brother of Hades, a silicon compilation language developed at Princeton University/MIT)
1985-Present: Demeter (sister of Zeus, used to implement Zeus, started at GTE Labs)
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Adaptive Programming

7. History (Cont’d) 1990: First traversal specifications
1995: Separation of Concerns by Huersch and Lopes started “untangling” movement.
Collaboration with Xerox PARC began
1996: Gregor Kiczales and his group further develop Aspect Oriented Programming
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Adaptive Programming

8. Law of Demeter
originally formulated as a style rule for designing object-oriented systems
Each unit should have only limited knowledge about other units: only units "closely" related to the current unit.
each unit should only talk to its friends
DO NOT TALK TO STRANGERS !!!
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Adaptive Programming

9. Law of Demeter
More specific case of Low Coupling Principle
The motivation for the Law of Demeter is to control information overload
When writing a method, one should not hardwire the details of the class structure into that method
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Adaptive Programming

10. Structure-Shy Behavior (Traversal Strategy)
Programming is shy if it hides details of other concerns it cuts across
Gathers the code describing the traversal in one place with minimal dependency on the class structure
Compliant with Law of Demeter
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Adaptive Programming

11. Structure-Shy Behavior (Traversal Strategy)
Allows one to specify strategies that ignore certain parts of the concrete structure
Lowers the coupling of code from the concrete structure
Lessens the dependency of code changes when structure changes
Idea is to capture the essential structure and ignore the rest.
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Adaptive Programming

12. Structure-Shy Behavior
An implementation of a concern C1 is C2-shy if:
The C1 implementation relies only on minimal information of C2 implementations.
The C1 implementation can adapt to small changes in C2 implementations.
The C1 implementation is loosely coupled with C2 implementations.
The C1 implementation can work with C2’ , C2’’ , C2’’’ which are close or similar to C2 implementations.
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Adaptive Programming

13. Structure-Shy Behaviour
ordinary program
better program
structure-shy
functionality
Components
structure
Aspect 1
avoid tangled programs
AOP
synchronization
Aspect 2
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Adaptive Programming

14. Propagation Patterns
Adaptive program is specified using a collection of propagation patterns.
Propagation patterns specify a set of related constraints in the adaptive program
Given a customizing Class Dictionary Graph, a propagation pattern produces an OO program denoted by the adaptive program it specifies
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Adaptive Programming

15. Class Dictionary Graph
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16. Class Dictionary Graph
Vertices
Construction Vertex : Abstraction of a classs definition
Alternation Vertex: Define union classes
Repetition Vertex : Represents lists
Edges
Alternation Edges: Represents alternative relationship
Construction Edges: Represents parts
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17. Class Dictionary Graph
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18. Propagation Graph
Customize a propagation pattern with class dictionary graph, its traversal specifications induce a set of paths
Propagation Graph:
Sum up the total salary of officers
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Adaptive Programming

19. Propagation Graph – Code Generation
For each vertex in the propagation graph:
A method is created with the signature given by the operation specification in the propagation pattern.
The body for this method contains as many calls as the given vertex has outgoing construction edges in the propagation graph.
Each call is made to the method with the same signature attached to the vertex target of the corresponding construction edge.
Finally, each wrapper code fragment in the propagation
pattern is prefixed or appended to the generated code for the vertex or edge it specifies.
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Adaptive Programming

20. Example busStops BusRoute BusStopList buses 0..* BusStop BusList
UML CLASS DIAGRAM
busStops
BusRoute
BusStopList
buses
0..*
BusStop
BusList
Example for developing strategies and writing adaptive programs
waiting
0..*
passengers
Bus
PersonList
Person
0..*
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Adaptive Programming

21. Collaborating Classes
find all people waiting at any bus stop on a bus route
busStops
BusRoute
BusStopList
buses
0..*
BusStop
BusList
waiting
0..*
passengers
Bus
PersonList
Person
0..*
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Adaptive Programming

22. Traversal Strategy from BusRoute through BusStop to Person busStops
BusStopList
buses
one method
for each red
class
0..*
BusStop
BusList
waiting
0..*
passengers
Bus
PersonList
Person
0..*
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Adaptive Programming

23. Traversal Strategy from BusRoute bypassing Bus to Person busStops
BusStopList
buses
0..*
BusStop
BusList
waiting
0..*
passengers
Bus
PersonList
Person
0..*
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Adaptive Programming

24. Robustness of Strategy
from BusRoute through BusStop to Person
villages
BusRoute
BusStopList
busses
VillageList
busStops
0..*
0..*
BusStop
BusList
Village
waiting
0..*
passengers
Bus
PersonList
Person
0..*
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Adaptive Programming

25. DJ: Implementation class BusRoute {
int countPersons(TraversalGraph WP) {
Integer result = (Integer)WP.traverse(this,
new Visitor() { int r ;
public void before(Person host){ r++; }
public void start() { r = 0;}
public Object getReturnValue()
{return new Integer ( r);}
});
return result.intValue(); }
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26. DJ: Implementation ClassGraph classGraph = new ClassGraph();
TraversalGraph WPTraversal = new TraversalGraph
(“from BusRoute via BusStop to Person”, classGraph);
int r = aBusRoute.countPersons(WPTraversal);
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27. Taxi driver analogy
Streets and intersections correspond to class graph
Traversal strategy determines how the taxi will navigate through the streets
You can take pictures before and after intersections
You can veto sub traversals
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Adaptive Programming

28. Development Tools DJ and AP Library Demeter/C++ DemeterJ
Demeter/StKlos
Dem/Perl5
Dem/C++
Dem/CLOS
Demeter/Object Pascal
this technology is catching on
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Adaptive Programming

29. Advantages of AP
Focus on the essence of a problem to be solved and leads to simpler and shorter than conventional object-oriented programs.
Promote reuse.
Robust to changes
Design matches program
More understandable code
Improved productivity
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Adaptive Programming

30. Conclusion We covered What Adaptive Programming is Law of Demeter
Traversal Strategies
Propagation Patterns
Development Tools
Advantages of Adaptive Programming
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31. References http://www.ccs.neu.edu/research/demeter
Adaptive Object Oriented Software
Karl Liebher
Adaptive Programming
Mohammed G. Gauda – Ted Herman
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32. QUESTIONS
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