Model-driven engineering is a powerful approach to build large-scale applications. However, an application's metamodel often remains static after the initial development phase and cannot be changed unless a new development effort occurs. Yet, end users often need to rapidly adapt their applications to new needs. In many cases, end users would know how to make the required adaptations, if only the application would let them do so. In this paper we present how we built a runtime-dynamic meta-environment into Smalltalk's reflective language model. Our solution offers the best of both worlds: developers can develop their applications using the same tools they are used to and gain the power of meta-programming. We show in particular that our approach is suitable to support end user customization without writing new code: the adaptive model of Magritte not only describes existing classes, but also lets end users build their own metamodels on the fly.

1. Magritte
A Meta-Driven Approach to Empower
Developers and End Users
Lukas Renggli
Stéphane Ducasse
Adrian Kuhn
University of Bern, Switzerland
Software Composition Group

2. Roadmap
Problem
Demo
Implementation
Evaluation
Questions

3. What is the problem?

4. Rapidly changing
requirements

5. End users would
know their requirements

7. What did we see?

8. Meta-driven
software

9. Developer defined
meta-model

10. End user defined
meta-model

11. Run-time dynamic
meta-model

12. Meta-
Metamodel
<described-by>
Metamodel
Developer
<described-by>
Domain Model
End User

13. Meta-
Metamodel
<described-by>
Metamodel
Magritte
Developer
<described-by>
Domain Model
Magritte
End User

14. How does it work?

15. Type
Object
Component
Component
Type 1 *
1 1
(a) Type-Square
* *
Property
Property
Type 1 *
Type
Object
[Yoder et al, 2001] Architecture and design of adaptive object models

16. Type
Object
Component
Component
Type 1 *
1 1
(a) Type-Square
* *
Property
Property
Type 1 *
Type
Object
[Yoder et al, 2001] Architecture and design of adaptive object models

17. attributes
attributes
1 1 * attributes
*
1
Object *
Object *
*
Object
*
description
description
Object
Object
Type
Type
description
Object
Type
attributes
Description *
Description * *
1
Description *

18. attributes
attributes
1 1 * attributes
*
1
Object *
Object *
*
Object
*
description
description
Object
Object
Type
Type
description
Object
Type
attributes
Description *
Description * *
1
Description *

19. attributes
attributes
1 1 * attributes
*
1
Object *
Object *
*
Object
*
description
description
Object
Object
Type
Type
description
Object
Type
attributes
Description *
Description * *
1
Description *

20. Describe Objects

21. Describe Descriptions

22. Describe Constraints

23. Describe Behavior

25. pen-source development environment for
programming language. Despite being the
ted language and environment, Smalltalk
ar ahead of its successors in promoting a
Squeak by Example
ment where everything is an object, and
run-time.
Smalltalk
ended for both students and developers,
ly through the Squeak language and
of a series of examples and exercises.
vailable under the Creative Commons
3.0 license. You can either download the
an buy a softcover copy from lulu.com.
available from the book's web page at
www.squeak.org
g, hosted by the University of Bern,
Squeak
dorsed by ESUG, the European Smalltalk
more about Smalltalk and ESUG, see
www.squeakbyexample.org
Black!•!Ducasse!•!Niers
2
by Example
Andrew P. Black, Stéphane Ducasse, Oscar Nierstrasz, Damien Pollet

26. Reflection

27. Integration with Tools

28. Class Extension

29. What can we do with it?

30. Automatic Views

32. Automatic Editors

35. Automatic Validation

36. Move Page

37. Automatic Reports

39. Automatic Querying

40. Automatic Persistency

41. What did we gain?

42. t rid of
Ge
Reduce recurrent work

43. Describe once,
get everywhere

44. Extensible
Object Model

45. Ru n-t ime
Adaptive object model

46. Code Generation

47. End users
customizability

49. Industrial Users

55. Aare
Workflow definition
and runtime system

56. Magritte
www.lukas-renggli.ch
[René Magritte, 1966] Decalcomania

58. LOC Comparison
Model View
1561 LOC 1812 LOC
44% 37%
View Model
1983 LOC 3078 LOC
56% 63%
SmallWiki Pier
Traditional Meta-described

59. Speed Comparison
9,000
8,190
6,750
4,500
2,250 2,456
0
Traditional Meta-Described