1. Atanas (Nasko) Rountev Ohio State University
Static Control-Flow Analysis for Reverse Engineering of UML Sequence Diagrams
Atanas (Nasko) Rountev
Ohio State University
with Olga Volgin and Miriam Reddoch

2. Example of a UML Sequence Diagram
start:X
p:A
m1()
m2()
m3()
create()
n:A
opt
m4()
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

3. Popular UML artifacts for modeling of object interactions
UML Sequence Diagrams
Popular UML artifacts for modeling of object interactions
Design-time sequence diagrams
Reverse-engineered sequence diagrams
Based on existing code
Iterative development; design recovery for software maintenance; software testing
Implemented in some commercial UML tools
Together ControlCenter (Borland)
EclipseUML (Omondo)
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

4. Reverse-Engineering Analyses
Dynamic analysis: tracks a set of representative run-time executions
Several research tools
Static analysis: examines only the code
Commercial tools (deficiencies)
Some research work (not comprehensive)
RED tool for Java: PRESTO group at OSU
URL: presto.cse.ohio-state.edu/red
Call chain analysis; control-flow analysis; object naming analysis; visualization and navigation; test coverage measurements
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

5. Representation of Intraprocedural Flow of Control
Given: the methods whose bodies will be used to construct the diagram
How should we represent the intraprocedural flow of control inside these bodies?
Solution: general algorithm for mapping a method’s CFG to UML 2.0 interaction fragments
Any reducible exception-free CFG
Precise mapping: preserves all call sequences
Subsequent diagram transformations
Lossless vs. lossy
Visualization and exploration
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

6. UML 2.0 Interaction Fragments
Opt, alt, loop, break; added generalized break
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

7. Phase I: Preprocessing
Analysis Stages
CFG
Phase I: Preprocessing
Phase II: Fragment Construction
Phase III: Transformations
Data Structure for Fragments
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

8. Phase I: Preprocessing
Post-dominance tree
Node n2 post-dominates n1 if all paths from n1 to exit go through n2
Immediate post-dominator; parent in the tree
Analyze branch nodes
What is the merge point for all branches?
Analyze loops
Nesting relationships
What is the merge point for all loop exits?
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

9. Post-dominance Tree PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

10. Branch Nodes and Branch Successors
Branch successor: node where the outgoing paths for a branch node merge
the branch
successor
of 3 is 6
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

11. Loops and Loop Successors
Reducible CFG: contains only natural loops
Loop successor: merge point of all paths exiting the loop
the loop
successor
of L is 12
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

12. Branch/Loop Successors Inside Loop L
Consider only edges inside L
Create a post-dominance tree for L and use it for:
branch successors for nodes in L
loop successors for loops nested in L
the branch
successor
of 7 is 10
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

13. Phase I: Preprocessing
Analysis Stages
CFG
Phase I: Preprocessing
Phase II: Fragment Construction
Phase III: Transformations
Data Structure for Fragments
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

14. Phase II: Fragment Construction
TOP 1
: i = -1
PatternEntry:getChars() 2
: s = e.getChars()
ALT
cond: s != null 1
String:charAt(0) 3 T
: s != null F
Vector:indexOf(e) 4
: e = s.charAt(0) 5
: i = patterns.indexOf(e)
LOOP
cond: i>= 0 1 F 6
: i>=0
BREAK
cond: i<0 1
breaks_from: LOOP T 1 F 7
: statusArray[i] !=0
OPT 1
cond: statusArray[i] !=0 T
Vector:elementAt(i) 8
: e1 = patterns.elementAt(i)
BREAK
cond: e1 != null 2
breaks_from: LOOP 9: 1
e1 != null T
MergeCollation:fixEntry(e1) F 10 11
: patterns.removeElementAt(i)
: fixEntry(e1)
Vector:removeElementAt(i)
12:
exit
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

15. Multi-level break fragments Multiple method exits
Various Issues
UML additions
Multi-level break fragments
Multiple method exits
Opt-like fragments: return fragments
Algorithm uses info about control dependencies
Exceptions (Java)
“throw e”: similar to method exit - throw fragment
Ignore catches and implicit exceptions
Node replication: the same CFG node may have to produce multiple identical diagram elements
e.g. due to short-circuit evaluation
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

16. Average Running Time per Method [milliseconds]
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

17. Methods Requiring Return/Throw Fragments
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

18. Methods Requiring Multi-level Break Fragments
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

19. Methods Requiring Node Replication
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05

20. Summary and Future Work
General and fast algorithm
Creates detailed and precise representation
Subsequent simplifications
Lossless: e.g. merge a fragment with the surrounding fragment [OSU-CISRC-3/04-TR12]
Lossy: e.g. give up on multi-level breaks
Interactive visualization [VISSOFT’05]
Collapse and un-collapse fragments; slice the diagram w.r.t. a fragment of interest
Re-implement in Eclipse and make public, together with the other analyses in RED
PRESTO Research Group - Ohio State University
Nasko Rountev - PASTE'05