Existing reverse-engineering tools use algorithms based on vague and verbose definitions of UML constituents to recover class diagrams from source code. Thus, reverse-engineered class diagrams are neither abstract nor precise representations of source code and are of little interest for software engineers. We propose a exhaustive study of class diagram constituents with respect to their recovery from C++, Java, and Smalltalk source code. Finally, we suggest a road-map to abstract and precise reverse-engineering. We exemplify our study by developing a tool to reverse-engineer Java programs in UML class diagrams abstractly and precisely. Such a reverse-engineering tool produces class diagrams that help software engineers in better understanding programs.

1. Yann-Gaël Guéhéneuc
© Yann-Gaël Guéhéneuc
This presentation has been given at APSEC 2004, the 2nd of December 2004, in Busan, Korea.
Software Engineering Laboratory
Department of Computing Science and Operations Research
University of Montreal
Systematic Study of UML Class
Diagram Constituents for their
Abstract and Precise Recovery
guehene@iro.umontreal.ca
2004/12/02

2. 2/25
Context
n UML is a standard
– Used in industry
– Taught in universities
n UML is not a standard
– Imprecise
– Heavy

3. 3/25
Problem
n But “lost” class diagrams
– Missing, out-of-date
n Maintenance > 50% of cost
– Program understanding > 50% of time
• Developers
• Maintainers
• Architecture
• Behaviour
• Design choices
• Implementation

4. 4/25
Problem (cont’d)
n Lack of automated recovery tools
– Class diagrams
• Abstract
– Concentrate the essential qualities of anything more
extensive or of several things
(≠ Graphical representations of source code)
• Precise
– Extent to which a given measurement agrees with a
standard value
(Original and–or expected class diagrams)

5. 5/25
Example

6. 5/25
Example
public class A { ... }
public class Example1 {
private A[] listOfAs = new A[10];
private int numberOfAs = 0;
public void addA(final A a) {
this.listOfAs[numberOfAs++] = a;
}
public A getA(final int index) {
return this.listOfAs[index];
}
public void removeA(final A a) {
// ...
}
public static void main(final String[] args) {
final Example1 example1 = new Example1();
example1.addA(new A());
// ...
}
}

7. 5/25
Example
public class A { ... }
public class Example1 {
private A[] listOfAs = new A[10];
private int numberOfAs = 0;
public void addA(final A a) {
this.listOfAs[numberOfAs++] = a;
}
public A getA(final int index) {
return this.listOfAs[index];
}
public void removeA(final A a) {
// ...
}
public static void main(final String[] args) {
final Example1 example1 = new Example1();
example1.addA(new A());
// ...
}
}

8. 6/25
Example (cont’d)

9. 6/25
Example (cont’d)
public class A { ... }
public class Example2 {
private List listOfAs = new ArrayList();
public void addA(final A a) {
this.listOfAs.add(a);
}
public A getA(final int index) {
return (A) this.listOfAs.remove(index);
}
public void removeA(final A a) {
this.listOfAs.remove(a);
}
public static void main(final String[] args) {
final Example2 example2 = new Example2();
example2.addA(new A());
// ...
}
}

10. 6/25
Example (cont’d)
public class A { ... }
public class Example2 {
private List listOfAs = new ArrayList();
public void addA(final A a) {
this.listOfAs.add(a);
}
public A getA(final int index) {
return (A) this.listOfAs.remove(index);
}
public void removeA(final A a) {
this.listOfAs.remove(a);
}
public static void main(final String[] args) {
final Example2 example2 = new Example2();
example2.addA(new A());
// ...
}
}

11. 7/25
Example (cont’d)

12. 7/25
Example (cont’d)
Precise

13. 7/25
Example (cont’d)
Precise
Association à Aggregation

14. 7/25
Example (cont’d)
Precise
Association à Aggregation
Abstract

15. 7/25
Example (cont’d)
Precise
Association à Aggregation
Abstract
List is not important

16. 8/25
Solution
n Systematic study of class diagram
constituents for their abstract and
precise recovery
– 34 constituents (UML meta-model)
– C++, Java, and Smalltalk
– Prototype tool

17. 9/25
Related Work
n Number of constituents of class
diagrams handled by tools
Recovered UML constituents in %
ArgoUML 7/34 21
Chava 7/34 21
Fujaba 7/34 21
IDEA 16/34 48
Rational Rose 8/34 24
Borland Together/J 8/34 24
Womble 9/34 28

18. 10/25
Hypotheses
n Class-based programming languages
n Class diagrams document design
during development and maintenance
n Context dependant definitions of the
constituents (⇒ incrementality)

19. 11/25
Systematic Study
n Classifier features
– Attribute üü
– Method üü
– Operations üû
• Abstract public methods
• Overloaded methods
• (Comments, documentation)
Abstract, Precise

20. 12/25
Systematic Study
n Classifier relationships
– Binary association üü
– Association end N/A
– Multiplicity üû
– Qualifier üû
– Association class ûû
– N-ary association ûû
– Aggregation üü
– Composition üû
– Generalisation ûü
– Dependency ûû
Abstract, Precise

21. 13/25
Systematic Study
n Classifiers
– Class üü
– Nested class ûü
– Type üü
– Implementation class üü
– Interface üü
– Parameterised class üü
– Bound Element üü
– Metaclass üü
– Powertype ûû
– Data Type üü
– Enumeration üü
– Utility class üü
Relationships
to Other from OtherClassifiers Attributes Operations Methods
Classifiers
Class ü ü ü ü ü
Implementation Class ü û ü û û
Interface û ü û û ü
Type ü ü û ü ü
Abstract, Precise

22. 14/25
Systematic Study
n Miscellaneous
– Stereotype üû
– Class pathname üü
– Importing packages üü
– Object N/A
– Composite object N/A
– Link N/A
– Instance of üü
– Derived element
– List compartment N/A
– Name compartment N/A
Abstract, Precise

23. 15/25
Discussion
n Consensual definitions?
n Base of comparison?

24. 16/25
Prototype Tool
n Ptidej
– Pattern Trace Identification, Detection, and
Enhancement in Java
• Also “breakfast” in French slang J
– Open framework for high-level program
analyses, visualisation, pattern detection
• More at www.ptidej.net
– Executable (.exe, .jar)
– Source code

25. 17/25
Prototype Tool (cont’d)
n Ptidej
Java
Model
Abstract and
Precise Model
Dedicated Parsers
Transformations
based on the
Systematic Study
PADL
Meta-Model
C++

26. 18/25
Prototype Tool (cont’d)
n Ptidej
Recovered UML constituents in %
ArgoUML 7/34 21
Chava 7/34 21
Fujaba 7/34 21
IDEA 16/34 48
Ptidej 21/34 62
Rational Rose 8/34 24
Borland Together/J 8/34 24
Womble 9/34 28

27. 19/25
Prototype Tool (cont’d)
n Ptidej
– Association, aggregation, and composition
binary class relationships
• Message sends
• Invocation sites
– Simple fields
– Arrays, collections
• Lifetime and exclusivity properties

28. 20/25
Prototype Tool (cont’d)
n Ptidej
– Classes, data types, implementation
classes, interfaces, types, utility classes
• Abstractness
• Attributes
• Methods (instance vs. class)
• Operations
• Relationships
• Super-classes

29. 21/25
Example revisited
public class A { ... }
public class Example1 {
private A[] listOfAs = new A[10];
private int numberOfAs = 0;
public void addA(final A a) {
this.listOfAs[numberOfAs++] = a;
}
public A getA(final int index) {
return this.listOfAs[index];
}
public void removeA(final A a) {
// ...
}
public static void main(final String[] args) {
final Example1 example1 = new Example1();
example1.addA(new A());
// ...
}
}

30. 21/25
Example revisited
public class A { ... }
public class Example1 {
private A[] listOfAs = new A[10];
private int numberOfAs = 0;
public void addA(final A a) {
this.listOfAs[numberOfAs++] = a;
}
public A getA(final int index) {
return this.listOfAs[index];
}
public void removeA(final A a) {
// ...
}
public static void main(final String[] args) {
final Example1 example1 = new Example1();
example1.addA(new A());
// ...
}
}

31. 22/25
Example revisited (cont’d)
public class A { ... }
public class Example2 {
private List listOfAs = new ArrayList();
public void addA(final A a) {
this.listOfAs.add(a);
}
public A getA(final int index) {
return (A) this.listOfAs.remove(index);
}
public void removeA(final A a) {
this.listOfAs.remove(a);
}
public static void main(final String[] args) {
final Example2 example2 = new Example2();
example2.addA(new A());
// ...
}
}

32. 22/25
Example revisited (cont’d)
public class A { ... }
public class Example2 {
private List listOfAs = new ArrayList();
public void addA(final A a) {
this.listOfAs.add(a);
}
public A getA(final int index) {
return (A) this.listOfAs.remove(index);
}
public void removeA(final A a) {
this.listOfAs.remove(a);
}
public static void main(final String[] args) {
final Example2 example2 = new Example2();
example2.addA(new A());
// ...
}
}

33. 23/25
Example revisited (cont’d)

34. 23/25
Example revisited (cont’d)
Precise

35. 23/25
Example revisited (cont’d)
Precise Abstract

36. 24/25
Conclusion
n Exhaustive and systematic study of
UML class diagram constituents
n Prototype tool implementing algorithms
for abstract and precise recovery
n Recovery of more constituents than any
other tools

37. 25/25
Future Work
n UML v2.0
n Other programming languages
– Eiffel
n Other source of information
– Comments, names
– Documentation
n Other diagrams
– Sequence diagrams + Integration
n Base(s) of comparison