Static Control-Flow Analysis for
Reverse Engineering of UML
Sequence Diagrams
Atanas (Nasko) Rountev
Ohio State University
with Olga Volgin and Miriam Reddoch
Example of a UML Sequence Diagram
start:X
p:A
m1()
m2()
m3()
create()
opt
n:A
m4()
PRESTO Research Group - Ohio State
University
Nasko Rountev PASTE'05
2
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
PRESTO Research Group - Ohio State
University 
Nasko Rountev PASTE'05
Together ControlCenter (Borland)
3
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.ohioPRESTO Research
Group - Ohio State
Nasko Rountev state.edu/red
University
PASTE'05

4
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
PRESTO
Research Group - Ohio
State
Nasko Rountev  Subsequent
diagram
transformations

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5
UML 2.0 Interaction Fragments

Opt, alt, loop, break; added
sd example
generalized
break
:MergeCollation
s:String
e:PatternEntry
patterns:Vector
example(e)
s = getChars()
ALT
i=charAt(0)
i=indexOf(e)
LOOP L
e1= elementAt(i)
OPT
BREAK L
fixEntry(e1)
removeElementAt(i)
PRESTO Research Group - Ohio State
University
Nasko Rountev PASTE'05
6
Analysis Stages
CFG
Phase I: Preprocessing
Phase II: Fragment Construction
Phase III: Transformations
Data Structure for Fragments
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University
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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
PRESTO
Group
- Ohio
State
Nasko
Rountev
 Research
What
is
the
merge
point
for
all
loop
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PASTE'05

8
Post-dominance Tree
1: i = -1
2: s = e.getChars()
12
T
6
7
9
11
4: e = s.charAt(0)
F
3
4
5
10
3: s != null
F
5: i = patterns.indexOf(e)
6: i>=0
8
T
F
2
7: statusArray[i] !=0
T
8: e1 = patterns.elementAt(i)
1
9: e1 != null
T
F
10: patterns.removeElementAt(i)
11: fixEntry(e1)
12: exit
PRESTO Research Group - Ohio State
University
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Branch Nodes and Branch Successors
Branch successor: node where the outgoing
paths for a branch node merge

1: i = -1
2: s = e.getChars()
12
T
6
7
9
11
4: e = s.charAt(0)
F
3
4
5
10
3: s != null
F
5: i = patterns.indexOf(e)
6: i>=0
8
T
F
2
1
the
branch
successo
r
of 3 is 6
PRESTO Research Group - Ohio State
University
7: statusArray[i] !=0
T
8: e1 = patterns.elementAt(i)
9: e1 != null
T
F
10: patterns.removeElementAt(i)
11: fixEntry(e1)
12: exit
Nasko Rountev PASTE'05
1
0
Loops and Loop Successors

Reducible CFG: contains only
natural loops
Loop successor: merge point of all
paths exiting
the loop
12
1: i = -1

2: s = e.getChars()
T
3: s != null
4: e = s.charAt(0)
6
7
9
F
5: i = patterns.indexOf(e)
11
F
6: i>=0
T
3
4
5
10
8
F
7: statusArray[i] !=0
T
the loop
success
1
or
of L is
12Group - Ohio State
PRESTO Research
2
University
8: e1 = patterns.elementAt(i)
9: e1 != null
T
F
10: patterns.removeElementAt(i)
11: fixEntry(e1)
12: exit
Nasko Rountev PASTE'05 11
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
1: i = -1
2: s = e.getChars()
T
3: s != null
4: e = s.charAt(0)
F
F
5: i = patterns.indexOf(e)
6: i>=0
T
6
F
7: statusArray[i] !=0
T
10
the
9
7
branch
successo
8
r
PRESTO Research Group
Ohio
of- 7
is State
10
University
8: e1 = patterns.elementAt(i)
9: e1 != null
T
F
10: patterns.removeElementAt(i)
11: fixEntry(e1)
12: exit
Nasko Rountev PASTE'05
1
2
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
1
3
Phase II: Fragment Construction
TOP
1: i = -1
PatternEntry:getChars()
2: s = e.getChars()
ALT 1 cond: s != null
String:charAt(0)
3
: s != null
Vector:indexOf(e)
4
5: i = patterns.indexOf(e)
: e = s.charAt(0)
LOOP 1 cond: i>= 0
F
6: i>=0
BREAK 1
T
F
7: statusArray[i] !=0
OPT 1
cond: i<0
breaks_from: LOOP 1
cond: statusArray[i] !=0
T
Vector:elementAt(i)
8 : e1 = patterns.elementAt(i)
9:
e1 != null
BREAK 2 cond: e1 != null
breaks_from: LOOP 1
T
MergeCollation:fixEntry(e1)
F
10 : patterns.removeElementAt(i)
11 : fixEntry(e1)
Vector:removeElementAt(i)
12: exit
PRESTO Research Group - Ohio State
University
Nasko Rountev PASTE'05
1
4
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- Ohio
produce
multiple
identical
PRESTO
Research
Group
State
Nasko
Rountev 
University
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5
Average Running Time per Method [milliseconds]
50
45
40
35
30
25
20
15
10
5
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by ex
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University
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0
Nasko Rountev PASTE'05
1
6
Methods Requiring Return/Throw Fragments
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
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jf
by lex
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big ked
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University
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0%
Nasko Rountev PASTE'05
1
7
Methods Requiring Multi-level Break Fragments
18%
16%
14%
12%
10%
8%
6%
4%
2%
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by ex
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University
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0%
Nasko Rountev PASTE'05
1
8
Methods Requiring Node Replication
45%
40%
35%
30%
25%
20%
15%
10%
5%
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jfl
by ex
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ch e
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big ked
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pu tor
sh
ba
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University
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htm
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Nasko Rountev PASTE'05
1
9
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 [OSUCISRC-3/04-TR12]
Lossy: e.g. give up on multi-level
breaks
 Interactive visualization [VISSOFT’05]
 Collapse and un-collapse fragments;
PRESTO Research
Group
- Ohio State w.r.t. a fragment
Nasko Rountev
slice the
diagram
of
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