Apposition

1
Apposition

• In order to fill the observed gap between the
  various phases of the object-oriented software
  development life-cycle, they should be regarded
  as different views on a common underlying
  software model.

2
Bijstelling
Om de waargenomen kloof tussen de verschillende
fasen van de objectgerichte software-ontwikkelings
levenscyclus te dichten, moeten deze fasen
beschouwd worden als verschillende gezichtspunten
op een gemeenschappelijk onderliggend
softwaremodel.
3
The OO Development Life-Cycle

• Layered approach to software development

analysis
high-leveldesign
implementation
low-leveldesign
more abstract
more concrete
4
Observed Problem

• Problem with different underlying models
• Need to implement similar tools repeatedly
• Need to maintain compatibility between tools
• Poor support for reverse and synchronous
  engineering
• Difficult to maintain consistency between layers
• architectural drift, software aging, erosion, ...
  
• problems with impact assessment
• Reasons
• no explicit link from more concrete to more
  abstract layer
• some of the more abstract information is absent
  in the more concrete layer
• architectural decisions implementation
  strategies based on non-functional requirements
• programming conventions design patterns

5
Example
abstract class Graphic() abstract void draw()
... ... class DrawingElt()Graphic() void
draw() ... ... class Picture()Graphic()
ListltGraphicgt graphics void draw()
IteratorltGraphicgt g(graphics)
for(g.first(),!g.empty(),g.next())
g.current()-gtdraw() ... ...
6
Vision

• Choose enhanced implementation as common
  underlying model
• Focus on implementation
• most essential part of software dev.
• more difficult, time-consuming, error-prone to
  write
• more complex
• Enhanced with
• more abstract information
• bidirectional link between code and abstract info
• Define each layer as abstract view on the
  implementation model
• Representation-independent
• Filter relevant information only

extra info implementation
7
Logic Meta Programming

• Enhance implementation code with meta layer
• To avoid cluttering code
• To enable reasoning about and manipulating the
  code
• Tight symbiosis between code and metalevel
• when editing software, meta-information is used
  to
• give feedback on impact of changes
• warn about breaches in more abstract layers
• metalevel is integrated with software development
  environment
• Use logic meta programming
• declarative approach
• evidence promising experiments at our lab

8
Evidence

• SOUL declarative reasoning framework for
  Smalltalk
• Automatic detection of design patterns in
  Smalltalk Wuyts98
• Detecting breaches of programming conventions
  when evolving Smalltalk code Wuyts98
• e.g. each instance variable should have a
  corresponding accessor method with the same name
• Checking conformance of Smalltalk code to
  software architecture MensWuyts99
• Extracting interaction diagrams from Smalltalk
  Richneral99
• Aspect-oriented programming DeVolder98
• Code optimisation TourweDeMeuter99