This document discusses enabling runtime change through explicit meta-objects. It proposes a system called Albedo that makes meta-objects explicit to allow runtime reflection and change. Albedo supports both structural and behavioral meta-objects to intercept and modify execution events like method calls and object creation. These meta-objects can be composed and extended to provide flexible and reusable runtime reflection.

1. Run-Time Evolution
through Explicit
Meta-Objects
Jorge Ressia, Lukas Renggli, Tudor Gîrba,
Oscar Nierstrasz
Tuesday, October 5, 2010
To enable change at run-time, a system must be self-aware and be able to fully reflect on
itself.

2. Tuesday, October 5, 2010
To enable change at run-time, a system must be self-aware and be able to fully reflect on
itself.

3. Instrospection
Tuesday, October 5, 2010
Query

4. Intercession
Tuesday, October 5, 2010
Modify

5. Structural Reflection
Tuesday, October 5, 2010

6. Classes
Objects
Methods
Instructions
Instance Variables
Tuesday, October 5, 2010

7. That is not enough
Tuesday, October 5, 2010

8. Dynamic
Representation
Tuesday, October 5, 2010
We need to reflect on the dynamic representation of a program, that is, the operational
execution.
This is called Behavioral Reflection pioneered by Smith in the context of Lisp

9. Behavioral Reflection
Tuesday, October 5, 2010
Behavioral reflection provides a way to intercept and change the execution of a program. It is concerned with execution
events, i.e., method execution, message sends, or variable assignments.

10. Behavioral Reflection
S mith
1982
Tuesday, October 5, 2010
Behavioral reflection provides a way to intercept and change the execution of a program. It is concerned with execution
events, i.e., method execution, message sends, or variable assignments.

11. Message Send
Message Receive
Method Lookup
Object Creation
State Read/Write
Tuesday, October 5, 2010

12. Tuesday, October 5, 2010

13. odA 5
C 99 1
McAffer
Tuesday, October 5, 2010

14. Is that all?
Tuesday, October 5, 2010
It is not possible to foresee all potential reification that might be required at runtime.

15. What if we need a
new reification?
Tuesday, October 5, 2010
It is not possible to foresee all potential reification that might be required at runtime.

16. Thesis
To e n a b l e r u n t i m e
change we must reify
Meta-objects explicitely
Tuesday, October 5, 2010

17. Albedo
Tuesday, October 5, 2010

18. Albedo
Structural Behavioral
Meta-objects Meta-objects
Tuesday, October 5, 2010

19. Structural
Meta-Object
Tuesday, October 5, 2010

20. add method
remove method
add state
remove state
Tuesday, October 5, 2010

21. Class
Object
Tuesday, October 5, 2010
- Removing accessors.

22. Class
Meta-object
Object
Tuesday, October 5, 2010
- Removing accessors.

23. Behavioral
Meta-Object
Tuesday, October 5, 2010

24. message send
message received
state write
state read
object creation
Tuesday, October 5, 2010

25. Class
Object
Tuesday, October 5, 2010
Method Look up

26. Class
Meta-object
Object
Tuesday, October 5, 2010
Method Look up

27. Class
Meta-object
M
Object
Object
Tuesday, October 5, 2010
Method Look up

28. Composables
Tuesday, October 5, 2010

29. Object Object
Tuesday, October 5, 2010

30. Meta-object
Object Object
Tuesday, October 5, 2010

31. Meta-object
Meta-object
Object Object
Tuesday, October 5, 2010

32. Meta-object
Meta-object
Object Object
Meta-object
Tuesday, October 5, 2010

33. Reusable
Tuesday, October 5, 2010

34. Meta-objects
Object
Tuesday, October 5, 2010

35. Meta-objects
Object
Object
Tuesday, October 5, 2010

36. Meta-objects
Object
Object
Object
Tuesday, October 5, 2010

37. Extensible
Tuesday, October 5, 2010

38. Partial Behavioral
Reflection
Tuesday, October 5, 2010

39. Partial Behavioral
Reflection
eflex
R 003 2
Tanter
Tuesday, October 5, 2010

40. Partial Behavioral
Reflection
eflex
R 003 2
Tanter
R eflec tivity
Denker 2008
Tuesday, October 5, 2010

41. AST
Tuesday, October 5, 2010
Examples?

42. AST
Tuesday, October 5, 2010
Examples?

43. AST
Tuesday, October 5, 2010
Examples?

44. Conclusions
Tuesday, October 5, 2010
- runtime
- flexible
- object oriented

45. Albedo
http://scg.unibe.ch/research/Albedo
Tuesday, October 5, 2010