static control-flow analysis for reverse engineering of uml sequence diagrams

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

Sequence DiagramsSequence Diagrams

Atanas (Nasko) RountevOhio State University

with Olga Volgin and Miriam Reddoch

PRESTO Research Group - Ohio StPRESTO Research Group - Ohio State Universityate University

Nasko Rountev - PASTE'0Nasko Rountev - PASTE'055

22

Example of a UML Sequence DiagramExample of a UML Sequence Diagram

start:X

m1()

p:A

m2()

n:A

m3()

create()

m4()opt



33

UML Sequence DiagramsUML 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)



44

Reverse-Engineering AnalysesReverse-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)

REDRED tool for Java: PRESTOPRESTO 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



55

Representation of Intraprocedural Flow of Representation of Intraprocedural Flow of ControlControl

Given: the methods whose bodies will be used to construct the diagram

How should we represent the intraintraprocedural 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



66

UML 2.0 Interaction FragmentsUML 2.0 Interaction Fragments Opt, alt, loop, break; added generalized break

sd example

s:String:MergeCollation patterns:Vector

example(e)

LOOP L

BREAK L

e:PatternEntry

ALT

s = getChars()

i=charAt(0)

i=indexOf(e)

OPT e1= elementAt(i)

fixEntry(e1)

removeElementAt(i)



77

Analysis StagesAnalysis Stages

CFG

Phase I: Preprocessing

Phase II: Fragment Construction

Phase III: Transformations

Data Structure for Fragments



88

Phase I: PreprocessingPhase 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?



99

12

3

11976

2

81054

1

3: s != null

2: s = e.getChars()

1: i = -1

4: e = s.charAt(0) 5: i = patterns.indexOf(e)

7: statusArray[i] !=0

6: i>=0

8: e1 = patterns.elementAt(i)

11: fixEntry(e1)

9: e1 != null

12: exit

10: patterns.removeElementAt(i)

FT

T

F

T

F

T

F

Post-dominance TreePost-dominance Tree



1100

3: s != null

2: s = e.getChars()

1: i = -1



6: i>=0


11: fixEntry(e1)

9: e1 != null

12: exit


FT

T

F

T

F

T

F

12

3

11976

2

81054

1

Branch Nodes and Branch SuccessorsBranch Nodes and Branch Successors Branch successor: node where the

outgoing paths for a branch node merge

the branch

successorof 3 is 6



1111

Loops and Loop SuccessorsLoops and Loop Successors

the loop successorof L is 12

3: s != null

2: s = e.getChars()

1: i = -1



6: i>=0


11: fixEntry(e1)

9: e1 != null

12: exit


FT

T

F

T

F

T

F

12

3

11976

2

81054

1

Reducible CFG: contains only natural loops Loop successor: merge point of all paths exiting

the loop



1122

Branch/Loop Successors Inside Loop LBranch/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

3: s != null

2: s = e.getChars()

1: i = -1



6: i>=0


11: fixEntry(e1)

9: e1 != null

12: exit


FT

T

F

T

F

T

F9

6

8

10

7

the branch

successorof 7 is 10



1133

Analysis StagesAnalysis Stages

CFG

Phase I: Preprocessing

Phase II: Fragment Construction

Phase III: Transformations

Data Structure for Fragments



1144

3 : s != null

2: s = e.getChars()

1: i = -1

4 : e = s.charAt(0) 5: i = patterns.indexOf(e)


6: i>=0

8 : e1 = patterns.elementAt(i)

11 : fixEntry(e1)

9: e1 != null

12: exit


FT

T

F

T

F

T

F

PatternEntry:getChars()

TOP

OPT

ALT

cond: statusArray[i] !=0

cond: s != null

Vector:elementAt(i)

String:charAt(0)

Vector:indexOf(e)

LOOP

cond: e1 != nullBREAK

MergeCollation:fixEntry(e1)

breaks_from: LOOP1

1

1

1

2

1

BREAK 1breaks_from: LOOPcond: i<0

cond: i>= 0

Vector:removeElementAt(i)

Phase II: Fragment ConstructionPhase II: Fragment Construction



1155

Various IssuesVarious 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



1166

Average Running Time per Method Average Running Time per Method [milliseconds][milliseconds]

0

5

10

15

20

25

30

35

40

45

50



1177

Methods Requiring Return/Throw FragmentsMethods Requiring Return/Throw Fragments

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%



1188

Methods Requiring Multi-level Break Methods Requiring Multi-level Break FragmentsFragments

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%



1199

Methods Requiring Node ReplicationMethods Requiring Node Replication

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%



2200

Summary and Future WorkSummary 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-[OSU-CISRC-3/04-TR12]3/04-TR12]

Lossy: e.g. give up on multi-level breaks Interactive visualization [VISSOFT’05][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 REDRED

static control-flow analysis for reverse engineering of uml sequence diagrams

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