Static Control-Flow Analysis for Reverse Engineering of UML Sequence Diagrams

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Static Control-Flow Analysis for Reverse
Engineering of UML Sequence Diagrams

• Atanas (Nasko) Rountev
• Ohio State University
• with Olga Volgin and Miriam Reddoch

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Example of a UML Sequence Diagram
startX
pA
m1()
m2()
m3()
create()
nA
m4()
opt
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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)

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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

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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 algorithm for mapping a methods 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

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UML 2.0 Interaction Fragments

• Opt, alt, loop, break added generalized break

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Analysis Stages
CFG
Phase I Preprocessing
Phase II Fragment Construction
Phase III Transformations
Data Structure for Fragments
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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?

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Post-dominance Tree
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Branch Nodes and Branch Successors

• Branch successor node where the outgoing paths
  for a branch node merge

the branch successor of 3 is 6
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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

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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
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Phase II Fragment Construction
TOP
1
i -1
PatternEntrygetChars()
2
s e.getChars()
cond s ! null
ALT
1
StringcharAt(0)
3
s ! null
T
F
VectorindexOf(e)
4
5
e s.charAt(0)
i patterns.indexOf(e)
LOOP
cond igt 0
1
F
6
igt0
BREAK
cond ilt0
1
breaks_from LOOP
1
T
7
F
statusArrayi !0
OPT
cond statusArrayi !0
1
T
VectorelementAt(i)
8
e1 patterns.elementAt(i)
cond e1 ! null
BREAK
2
breaks_from LOOP
1
9
e1 ! null
T
MergeCollationfixEntry(e1)
F
11
fixEntry(e1)
10
patterns.removeElementAt(i)
VectorremoveElementAt(i)
12
exit
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Various Issues

• UML additions
• Multi-level break fragments
• Multiple method exits
• Opt-like fragments return fragments
• Algorithm uses 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 elements
• e.g. due to short-circuit evaluation

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Average Running Time per Method milliseconds
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Methods Requiring Return/Throw Fragments
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Methods Requiring Multi-level Break Fragments
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Methods Requiring Node Replication
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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 VISSOFT05
• 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

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• Questions?