This PhD thesis by István Ráth focuses on event-driven model transformations in domain-specific modeling languages. The thesis contains 3 parts: 1) developing concepts for event-driven graph transformations based on incremental pattern matching, 2) applying these concepts to provide advanced language engineering features like simulation, and 3) integrating modeling tools using change-driven transformations. The research aims to address challenges in scalability, usability and tool integration for model-driven software engineering.

1. Event-driven Model Transformations in
Domain-specific Modeling Languages
PhD thesis
István Ráth
Budapesti Műszaki és Gazdaságtudományi Egyetem
Méréstechnika és Információs Rendszerek Tanszék

2. Introduction

3. Software Engineering by Domain-specific Modeling

4. Challenges
Complexity of modeling
environments
• Multi-aspect modeling,
language families,
product lines, …

5. Challenges
Scalability of MDE
toolchains
• Large models vs.
incremental change
propagation
• Tool integration in
heterogeneous
environments

6. Challenges
Usability issues of DSMLs
• Abstraction: abstract-
concrete syntax
• Dynamics: execution
semantics

7. Research goals
Advanced language Tool integration
engineering features
Change
propagation
Abstraction
Model Incremental
transformations code
generation
Simulation
“Middleware”
for MDSE
Multi-aspect
DSM complexity and usability
modeling challenges
 Advanced language engineering solutions

8. Advanced language engineering

9. Motivation: limited abstractions
 Limitations of abstract-concrete syntax
representation in DSM language engineering
frameworks
 Usability problem!

10. Separating abstract and concrete syntax
 What?
Abstract Concrete
o concrete syntax diagrams
syntax syntax
o abstract syntax logical model
 Why? Test : Class Test
o reduce complexity for the user
ID : Attribute
o Give more power
ID: id0
to the language engineer
“id0” :String

11. Objectives
 Arbitrary mapping
o abstraction o diagram-specific
o aggregation elements
o decorators
Logical model Diagram
h0
p0 : Place
:token :token :token 3
t0:Token t1:Token t2:Token

12. Solution
 Bi-directional mapping
o goal: arbitrary mapping
o means: event-driven transformations (EDT)
Logical model Diagram model Diagram
:model
p0 : Place _p0 : PlaceFigure h0
:token :token :token EDT :property
3
t0:Token t1:Token t2:Token tokenCount
:Property

13. Motivation: no design-time simulation support
 Dynamic semantics specification and execution still a
missing feature from industrial DSM environments
 Dedicated simulators serve a different purpose
 General case: execution semantics introduced only during code
generation phase  delayed appearance of design errors

14. Design-time simulation
 Discrete Event System Specification (DEVS)
o Denotational semantics (specified by event-driven GT
rules)  generic approach
o Supports state automata, Kripke structures, Petri nets,
DFNs, BPEL/BPMN, UML statecharts, …
 Execution modes
o Interactive (guided debugging)
o Automatic (stochastic)

15. Simulation efficiency
Sparse Petri net benchmark
1000000
Viatra/RETE
100000 (x1k)
Execution time (ms)
10000
Viatra/LS (x1k)
1000
100 Viatra/RETE
(x1M)
10
100 1000 10000 100000
Petri net size

16. Thesis 2: automatic model transformations in domain-specific languages
2.1. Multi-aspect modeling for DSMLs based on multiple instantiation
and metamodel hierarchies
2.2. Complete separation of abstract and concrete syntax
representations
2.3. Design-time interactive simulation (specification and execution
semantics)
2.4. Efficient implementation techniques, verification by benchmarking
Collaboration
2.2. András Ökrös (MSc student)
2.3. Dávid Vágó

17. Important related publications
Journal paper
 István Ráth, András Ökrös, and Dániel Varró. Synchronization of abstract and concrete syntax in
domain-specific modeling languages. Software and Systems Modeling, 9:453–471, 2010.  6 citations
International Conferences
 Ajab Khan, Reiko Heckel, Paolo Torrini, and István Ráth. Model-based stochastic simulation of P2P
VoIP using graph transformation. 17th International Conference on Analytical and Stochastic Modeling
Techniques and Applications, 2010.  3 citations
 Paolo Torrini, Reiko Heckel, and István Ráth. Stochastic simulation of graph transformation systems.
Fundamental Approaches to Software Engineering, 6013/2010 LNCS pp. 154–157.  3 citations
 István Ráth, Dávid Vágó, and Dániel Varró. Design-time simulation of domain-specific models by
incremental pattern matching. The IEEE Symposium on Visual Languages and Human-Centric
Computing, VL/HCC 2008 pp. 219–222. Acceptance rate: 29%.  2 citations
 István Ráth and Dániel Varró. Challenges for advanced domain-specific modeling frameworks.
International Workshop on Domain Specific Program Development(DSPD2006), Nantes, France, July
2006.  7 citations
National conferences
 István Ráth. Modelltranszformációk integrált alkalmazása domain-specifikus nyelvekben. In Tavaszi
Szél Konferenciakiadvány, 2009.
 István Ráth. Declarative mapping between abstract and concrete syntax of domain- specific visual
languages. In The Proceedings of the Fifth Conference of PhD Students in Computer Science, 2006.

18. Research goals
Advanced language Tool integration
engineering features
Change
propagation
Abstraction
Model Incremental
transformations code
generation
Simulation
“Middleware”
for MDSE
Multi-aspect
Efficiency
modeling for language engineering
Integrated MTs
 new execution model

19. Event-driven transformations

20. Motivation
 Domain-specific modeling applications don’t align
well with the batch execution model
o Model/view synchronization
o Model queries and reports
modification
Key ideas:
Source model S1 S2 •
S3 Correlate events to
Sn
model changes
t tL transformation tL
• Capture formally by
tL
context graph pattern match
update set changes
Target model T1 T2
• Adapt graph
T3 Tn
transformations to
specify reactions

21. Graph Transformations in VIATRA2
LHS RHS
a1:inarc a2:outarc a1:inarc a2:outarc
Place Tran. Place Place Tran. Plan
ttn1:tokens tkn2:tokens
Token Token
matching updating
Phases of GT matching
– Pattern Matching phase
– Updating phase: delete+ create
Pattern Matching is the most critical issue from performance viewpoint
 Matches can be cached and updated incrementally by RETE nets
 Changes in the match sets can be detected efficiently

22. Event-driven graph
transformations C
C
D
Conditions
Transaction1
U
Incremental pattern
matcher C
Notification
Events D
D
Matching set delta monitor U
fall Model Store
MS(PA)
Execution
Commit
Engine
rise trigger
Transaction2
MS(PB)
actions
Transactions

23. Event-driven graph
transformations C
C
D
Conditions
Transaction1
U
Incremental pattern
matcher C
Notification
Events D
D
Matching set delta monitor U
fall Model Store
Event-Condition-Action
MS(PA) formalism Execution
Commit
• Adapted from expert systems Engine
• Specification language: graph triggers
• Execution semantics: priority queue automaton
rise trigger
Transaction2
MS(PB)
actions
Event-driven Transformations
• Run in the background
• React when necessary
• Model/view synchronization, change processing, … Transactions

24. Thesis 1: event-driven model transformations
1.1. Concepts for event-driven GT based on incremental pattern
matching
1.2. Execution semantics based on a queue automaton model
1.3. GT-based specification language: graph triggers
1.4. Efficient implementation techniques and a software
framework, verification by benchmarking
Collaboration
1.4. András Ökrös, Gábor Bergmann (MSc students)

25. Important related publications
Journal paper
 István Ráth, András Ökrös, and Dániel Varró. Synchronization of abstract and concrete syntax in
domain-specific modeling languages. Software and Systems Modeling, 9:453–471, 2010. 6
citations
International conferences
 István Ráth, Gábor Bergmann, András Ökrös, and Dániel Varró. Live model transformations
driven by incremental pattern matching. International Conference on Model Transformations
(ICMT2008), 5063/2008 LNCS, pp 107–121. Acceptance rate: 31%.  10 citations
 Gábor Bergmann, Ákos Horváth, István Ráth, and Dániel Varró. Efficient model transformations
by combining pattern matching strategies. International Conference on Model Transformations
(ICMT2009), 5563/2009 LNCS, pp 20–34. Acceptance rate: 23%  4 citations
 Gábor Bergmann, Ákos Horváth, István Ráth, and Dániel Varró. A benchmark evaluation of
incremental pattern matching in graph transformation. International Conference on Graph
Transformations, 5214/2008 LNCS, pp. 396–410. Acceptance rate: 40%. 11 citations
 Gábor Bergmann, András Ökrös, István Ráth, Dániel Varró, and Gergely Varró. Incremental
pattern matching in the VIATRA transformation system. 3rd International Workshop on Graph
and Model Transformation. 30th International Conference on Software Engineering, 2008.  9
citations

26. Applications in tool integration

27. Research goals
Advanced language Tool integration
engineering features
Change
propagation
Abstraction
Model Incremental
transformations code
generation
Simulation
“Middleware”
for MDSE
Multi-aspect
modeling
New applications
 new execution infrastructure

28. Tool integration chains
Tool k
Tool 3 (documentation)
Tool 1 (model annotation)
(modeling)
Tool n
(code generator)
Tool 2
(analysis)
Tool m
(test generator)
Tool x (test
bench)

29. Tool integration chains
Tool k
Tool 3 (documentation)
Tool 1 (model annotation)
(modeling)
Tool n
(code generator)
Tool 2
(analysis)
Challenge 1: Tool m
Efficient change (test generator)
propagation
Tool x (test
bench)

30. Change-driven transformations
 Incremental change propagation
Source model Traceability model Target model
MA TR MB
changeA changeB
Change-driven transformations
M’A TR’ M’B
Model-based
domain- Model
independent transformations for
change change processing
representation

31. Incremental and asynchronous code generation by CDTs
MA TR MB
changeA CMB
Asynchronous CDT
jPDL
Process
M’A TR’ M’B Description
IF
JBoss Workflow Engine
Graphical DSML <node name=“Interface Type Mapping”>
<action name=“UML2SAL Transformation”
class = “…”>
<toolId>UML2SAL transformer</toolId>
<functionId>UML2SAL</functionId>
<returnType>SALModel</returnType>
<params>
<entry>
<key>umlModel</key><value>...<value>
</entry>
</params>
</action>
<transition from=“initial_node”
to=“TCG-with-SAL-ATG” />
</node>

32. Incremental and asynchronous code generation by CDTs
MA TR MB
2 3
changeA CMB
Asynchronous CDT
jPDL
Process
M’A TR’ Description
IF 4 M’ B
JBoss Workflow Engine
Graphical DSML <node name=“Interface Type Mapping”>
<action name=“UML2SAL Transformation”
class = “…”>
<toolId>UML2SAL transformer</toolId>
<functionId>UML2SAL</functionId>
<returnType>SALModel</returnType>
<params>
<entry>
5
<key>umlModel</key><value>...<value>
1 </entry>
</params>
</action>
<transition from=“initial_node”
to=“TCG-with-SAL-ATG” />
</node>

33. Integration challenges
Tool k
Infrastructural challenges: (documentation)
• Many tools
• Many formats Tool 3
Tool 1
(modeling) (model annotation)
• Many (types of) users
• Collaborative data access Tool n
(code generator)
• Process management
Tool m
(test generator)
Solution:
Tool x (test bench)
Tool 2 SENSORIA Development Environment
(analysis) • Tool integration framework
• Model-based workflow orchestrations
• Distributed infrastructure based on a
model bus

34. Thesis 3: Tool integration based on change-driven transformations
3.1. Concept of change-driven transformations
3.2. New implementation techniques for incremental code generation by CDTs
3.3. Remote service invocation in the SENSORIA Development Environment
3.4. Implementation architecture for tool integration
3.5. Model-based framework for development workflows and synchronization
Collaboration
3.3. Ádám Horváth (MSc student)
3.4-3.5. Dr. Balázs Polgár & others

35. Important related publications
Book chapters
 István Ráth and Philip Mayer. The SENSORIA Development Environment. Book chapter in: Rigorous
Software Engineering for Service-Oriented Systems: Results of the SENSORIA project on Software
Engineering for Service-Oriented Computing, Springer, 2010 (Accepted).
 András Balogh, Gábor Bergmann, György Csertán, László Gönczy, Ákos Horváth, István Majzik, András
Patariza, Balázs Polgár, István Ráth, Dániel Varró, Gergely Varró. Workflow-driven tool integration
using model transformations. Book chapter in: Graph Transformations and Model-Driven
Engineering, 5765 LNCS, pp. 224–248.  1 citation
Journal paper
 Bergmann Gábor, István Ráth, Gergely Varró, and Dániel Varró. Change-driven model transformations:
Change (in) the rule to rule the change. Journal of Software and Systems Modeling, 2011 (Accepted).
International conferences
 István Ráth, Gergely Varró, and Dániel Varró. Change-driven model transformations. Model Driven
Engineering Languages and Systems, 12th International Conference, MODELS 2009. 5795/2009 LNCS.
Springer Best Paper Award and ACM Distinguished Paper Award; Acceptance rate: 18%.  2 citations
 Balázs Polgár, István Ráth, Zoltán Szatmári, and István Majzik. Model-based Integration, Execution and
Certification of Development Tool-chains. The 2nd ECMDA Workshop on Model-Driven Tool and
Process Integration, 2009.  1 citation

36. Summary

37. New results
Event-driven transformations by incremental pattern matching
• Specification language
• Execution semantics and infrastructure
Advanced language engineering by EDTs
• Interactive/stochastic simulation of dynamic semantics
• Abstract-concrete synchronization
Tool integration by change-driven transformations
• Incremental code generation
• Incremental change propagation to deployed models

38. Applications of new results in the VIATRA2 project
 VIATRA2: state-of-the-art graph transformation
framework
o Event-driven transformation engine
o ViatraDSM: domain-specific modeling front-end
 Collaborative follow-up research
o GraTS: stochastic simulator developed with the
University of Leicester
o EMF-IncQuery: EMF-based implementation platform
for all of the new results

39. Applications in EU projects
 DSM tools and incremental transformations
o Development workflow modeling
o Model synchronization,
change impact analysis
for requirements modeling
 Tool integration
o SENSORIA Development Environment
• software engineering for SOA
SENSORIA
• automated configuration generation
Software Engineering for
• formal verification by model checking
o MOGENTES extended tool integration framework
Service-Oriented Overlay
• automated test generation for railway systems
Computers

40. Publication overview
 Number of publications: 28
o Book chapters: 3
o International journal articles: 5
o International conference papers: 15
o National conference papers: 4
 Peer reviewed: 24
 Independent citations: 81, h-index: 6
 ACM Distinguished Paper and Springer Best Paper
Awards at the MODELS 2009 Conference

41. Answers to reviewers
Prof. Dr. Richard Paige

42. Remark 1
„While the thesis demonstrates the breadth of
application of event-driven transformations, the
introduction of the thesis might be improved by
focusing more on event-driven
transformations, perhaps by including one or two
coherent, concise scenarios where event-driven
transformations are the most suitable approach to
apply solving the problem. These scenarios are
straightforward to produce, and may improve
readability.”

43. Answer
 “Typical” EDT scenarios
o Model synchronization
o Well-formedness constraint evaluation
o Simulation
o Traceability management

44. Remark 2
„The breadth of applicability of the concepts outside
of the VIATRA2 framework would be strengthened
with either more detailed comparison with related
model management frameworks (oAW, AMMA and
Epsilon come to mind), or by summarising briefly
how the concept of event driven transformations
could be supported in other approaches. At the
moment, the thesis is presented almost entirely in
the context of VIATRA2; I am convinced that the
work is more generally applicable, but the thesis
could help the community more by synthesising
lessons learned that could help other model
management framework developers.”

45. Answer
 Key: notion of event
 Transformation needs to be split into two major
phases
o Query: Pattern matching-based approach for queries
supported by EMF-IncQuery over EMF models
o Model manipulation: EMF-based MT tools can be
invoked
o Care needs to be taken for technological issues
(parameter passing, …)
 Other approaches for incremental queries also
feasible (Drools, Egyed’s inconsistency
management framework, …)

46. Question 1
„I would ask them, in particular, about the amount
of context needed to run an event
transformation, and about the relationship
between event-driven and batch transformation
(i.e., what problems may occur when having batch
and event-driven transformations interact).”

47. Answer
 Context
o Detection of changes: match sets of patterns
o Global (session) variables
 Event-driven vs. batch transformations
o EDT lifecycle can be managed by BTs
o BT (modules) can be called by EDTs
o Possible problems
• Parameter passing
• execution timeout
 Open research question: how to transform an existing
BT into an EDT?
o Currently under investigation

48. Question 2
„I would also ask about the relationship between
event-driven transformations and complex event
processing engines, and the extent to which the
event infrastructure can deal with large numbers
of events.”

49. Answer
 Event processing engines
o Drools
o IBM WebSphere JRules (ILOG)
o Esper
 Slight difference in the notion of event
o Explicit events vs. inferred events
o Adaptation very well possible as shown by ongoing
research
 Keys to Scalability
o (Filtering)
o Hybrid PM
• Combine INC + LS strategies

50. Answers to reviewers
Prof. Dr. Tibor Gyimóthy

51. Question 1
„The thesis uses Petri nets as example. Did you
make experiments with real life domain specific
languages regarding any of your contributions?
(For example AUTOSAR is mentioned in Chapter 6
in connection with limitations of GMF.)”

52. Answer
 DSMLs for academic prototypes
o E-R, Petri net, UML profile adaptations, …
 DSMLs for workflow modeling
(SENSORIA, MOGENTES)
 Queries for AUTOSAR (collaboration with OptXware)
 Model synchronization in the SecMER tool
(SecureChange)
 New work (not included in thesis):
o DSML synthesis based on ontologies
o Quick fix generation for BPMN
o Other industrial applications

53. Question 2
„In Section 5.4 when performance of event-driven
transformation engine is evaluated, it is stated
that practical model size is below 5000 nodes. How
is this number estimated?”

54. Answer
“It is important to note that for practical model sizes
(e.g. below the 5000 node count range), the event-
driven VIATRA/RETE engine can perform a
synchronization affecting a considerable portion of the
model in the 10-500 msec range which makes the
approach very suitable for interactive applications.”
 Will be reworded
 Illustrative example of what might be considered
practical
 In general, this depends very much on the concrete
application
o scalability limit of our engine: 10^6 model elements

55. Question 3
„Design time model simulation can be controlled
through a user interface of the ViatraDSM
framework. Model elements can be decorated
using an API (in Figure 7.4 fireable transitions are
colored.) What kind of services are provided by
this programming interface? Beyond modifying
model elements, is there a possibility for example
to define regions – set of elements – and modify
their properties together?”

56. Answer
 ViatraDSM’s model access and manipulation API
o Domain-specific queries (types)
o Basic CRUD
o Access to concrete syntax (arbitrary customization
w.r.t. Draw2D possible)
 Generic queries (regions of elements)
o Possible by graph patterns
o Can be invoked from anywhere in the code

57. Question 4
„In Chapter 8 change-driven transformations are
introduced, where change impact analysis is
named as an application. As I could not find
[4], please explain the main results shortly. Give
an overview on other impact analysis techniques
(for example model level slicing) compared to
your solution.”

58. Answer
 Impact analysis by slicing
o Change the program  calculate the set of affected parts of the
program (control or data dependence)
 Model slicing
o Change the model  calculate a simplified set of (affected)
models
• Preserving semantics w.r.t. the sliced data
• Make formal analysis easier/faster
o Relies on a formalization of the language (e.g. class invariants
and operation pre/postconditions in UML)
 Impact analysis in SecureChange
o interpretation of the model is performed by humans, so only
guidance is given
o Solved by change patterns defined on interconnected models