Graph patterns provide a declarative formalism to describe model queries used for several important engineering tasks, such as well-formedness constraint validation or model transformations. As different pattern matching approaches, such as local search or incremental evaluation, have different performance characteristics (smaller memory footprint vs. smaller runtime), a wider range of practical problems can be addressed. The current paper reports on a novel feature of the EMF-IncQuery framework supporting local search-based pattern matching strategy to complement the existing incremental pattern matching capabilities. The reuse of the existing pattern language and query development environment of EMF-IncQuery enables to select the most appropriate strategy separately for each pattern without any modifications to the definitions of existing patterns. Furthermore, a graphical debugger component is introduced that visualizes the execution of the search process, helping to understand how complex patterns behave. This tool paper presents the new pattern matching feature from an end user’s view- point while the scientific details of the pattern matching strategy itself are omitted. The approach is illustrated on a case study of automated identification of anti-patterns over program models created from Java source code.

1. Local Search-based
Pattern Matching Features in
EMF-IncQuery
2015. 07. 22. 1Local search-based pattern matching features in EMF-IncQuery
Márton Búr, Zoltán Ujhelyi, Ákos Horváth, Dániel Varró
Presenter: Ábel Hegedüs
IncQuery Labs Ltd.
Budapest University of Technology and Economics

2. Anti-pattern Detection in Java Programs
2015. 07. 22. 2Local search-based pattern matching features in EMF-IncQuery
public class StringLiteralCompareTest {
public StringLiteralCompareTest srcVar;
@Override
public boolean equals(Object other) {
return super.equals(other);
}
public void test() {
srcVar.equals("source");
}
}

3. Anti-pattern Detection in Java Programs
2015. 07. 22. 3Local search-based pattern matching features in EMF-IncQuery
public class StringLiteralCompareTest {
public StringLiteralCompareTest srcVar;
@Override
public boolean equals(Object other) {
return super.equals(other);
}
public void test() {
srcVar.equals("source");
}
}
EMF metamodel of Java programs (part)

4. Anti-pattern Detection in Java Programs
2015. 07. 22. 4Local search-based pattern matching features in EMF-IncQuery
public class StringLiteralCompareTest {
public StringLiteralCompareTest srcVar;
@Override
public boolean equals(Object other) {
return super.equals(other);
}
public void test() {
srcVar.equals("source");
}
}
Instance model in EMF editor

5. Anti-pattern Detection in Java Programs
2015. 07. 22. 5Local search-based pattern matching features in EMF-IncQuery
public class StringLiteralCompareTest {
public StringLiteralCompareTest srcVar;
@Override
public boolean equals(Object other) {
return super.equals(other);
}
public void test() {
srcVar.equals("source");
}
}
String Literal as Compare Parameter
(anti-pattern as graph pattern)
inv: MethodInvocation
name = “equals”
m: NormalMethod
arg: StringLiteral
op: Literal
invokes operand
argument
check count
matches == 1
: Expression

6. Pattern Matching Strategies
2015. 07. 22. 6Local search-based pattern matching features in EMF-IncQuery
Local Search
• Executes a search plan
• Lower memory requirements
• Tools: ATL, GrGen.net, FUJABA, …
Incremental
• Maintains a cache structure
• Efficient recalculation
• Tools: EMF-IncQuery, Drools, ...

7. Local-search Based Pattern Matching
2015. 07. 22. 7Local search-based pattern matching features in EMF-IncQuery
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1

8. Local-search Based Pattern Matching
2015. 07. 22. 8Local search-based pattern matching features in EMF-IncQuery
Normal Method
1
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1

9. Local-search Based Pattern Matching
2015. 07. 22. 9Local search-based pattern matching features in EMF-IncQuery
Normal Method
1
2
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1
name: “equals”

10. Local-search Based Pattern Matching
2015. 07. 22. 10Local search-based pattern matching features in EMF-IncQuery
Normal Method
Method
Invocation
invokes
1
2
3
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1
name: “equals”

11. Local-search Based Pattern Matching
2015. 07. 22. 11Local search-based pattern matching features in EMF-IncQuery
Normal Method
StringLiteral
Method
Invocation
invokes
1
2
3
6
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1
name: “equals”

12. Local-search Based Pattern Matching
2015. 07. 22. 12Local search-based pattern matching features in EMF-IncQuery
Normal Method
StringLiteral
Identifier
Method
Invocation
invokes
1
2
3
6
8
Find all m that m ∈ NormalMethod
Attribute test: m.name=="equals”
Find inv that inv.invokes → m
Count of inv.argument → arg is 1
Find arg that inv.argument → arg
Instance test: arg is a StringLiteral
Find op that inv.operand → op
NEG: op is not a Literal8
7
6
5
4
3
2
1
name: “equals”

13. EMF-IncQuery
2015. 07. 22. 13Local search-based pattern matching features in EMF-IncQuery
Runtime
Incremental
queries using
Rete backend
Local search
backend
IDE
Language
Code
generator
Development
tools
Query
Explorer
Local Search
Debugger

14. Local Search Runtime
2015. 07. 22. 14Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Graph
patterns

15. Local Search Runtime
2015. 07. 22. 15Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Graph
patterns
• Calculates matches
• Manages model indexes

16. Local Search Runtime
2015. 07. 22. 16Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Rete backend
Graph
patterns

17. Local Search Runtime
2015. 07. 22. 17Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Rete backend
Graph
patterns
Default (incremental)
query executor

18. Local Search Runtime
2015. 07. 22. 18Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Rete backend
Graph
patterns
Pattern matches

19. Local Search Runtime
2015. 07. 22. 19Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Local search backend
Planner
Graph
patterns
Pattern matches
• Initializes search plans
• Reuses pre-populated
model indexes

20. Local Search Runtime
2015. 07. 22. 20Local search-based pattern matching features in EMF-IncQuery
IncQuery Engine
Model
Local search backend
Planner Matcher
Graph
patterns
Pattern matches
• Executes search plans
• Based on depth-first search

21. EMF-IncQuery IDE
2015. 07. 22. 21Local search-based pattern matching features in EMF-IncQuery

22. EMF-IncQuery IDE
2015. 07. 22. 22Local search-based pattern matching features in EMF-IncQuery
Query Editor
Defines graph patterns
Model Editor
EMF-based editor
Query Explorer
Displays query results

23. Local Search Debugger
2015. 07. 22. 23Local search-based pattern matching features in EMF-IncQuery
Step-by-step execution of search plans
• Visualizes search plans
• Visualizes (partial) query results

24. Local Search Debugger
2015. 07. 22. 24Local search-based pattern matching features in EMF-IncQuery
Step-by-step execution of search plans
• Visualizes search plans
• Visualizes (partial) query results
Local Search Debugger
• Based on local search
• Visualizes query
structure
• Step-by-step
execution
Query Explorer
• Relies on incremental
query evaluation
• Reacts on model
changes
• Results can be filtered

25. DEMO
2015. 07. 22. 25Local search-based pattern matching features in EMF-IncQuery

26. Performance Characteristics – 1.
2015. 07. 22. 26Local search-based pattern matching features in EMF-IncQuery
1
10
100
1000 10000 100000
SEARCHTIME(S)
PROGRAM SIZE (LOC)
LS INC LS (100) INC (100) LS INC LS (100) INC (100)
Incremental approach is beneficial
in case of re-evaluation

27. Performance Characteristics – 2.
2015. 07. 22. 27Local search-based pattern matching features in EMF-IncQuery
1
10
100
1000
10000
100000
1000 10000 100000 1000000 10000000
MEMORYUSAGE(MB)
PROGRAM SIZE (LOC)
LS INC LS INC
Local search works
uses less memory

28. Summary
Local search based pattern matcher
• Alternative execution strategy
• Reuses existing infrastructure
Search Plan Debugger
• Step-by-step execution of search plans
• Complements Query Explorer
Future plans
• Enhanced search plan generation
• Hybrid pattern matching
2015. 07. 22. 28Local search-based pattern matching features in EMF-IncQuery