Graph Transformation for Model Transformation

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Graph Transformation for Model Transformation

• Arend Rensink
• University of Twente

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Overview

• Scenario
• Outline of the presentation
• Requirements
• Principles
• Example
• Practice
• Next step
• Final words

A-Model
A-B Trafo
B-Model
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Requirements What do we need?

• Reasoning about models
• Instances of different meta-models
• Need common representation
• Idea graphs as common representation
• Powerful yet simple
• Natural for many models
• Theory of graph transformation available
• Some aspects not covered well
• Cardinality and inheritance in meta-models
• Ordered associations
• Attributes

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Example ASG to FG

• Abstract Syntax Graph model

0..1
next
Statement
body
else
then
1
0..1
1
Assign
If
While
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Example ASG instance

• Program
• ready falsewhile (! ready) if (x lt max)
  x xx ready true else ready
  false

• Graph

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Target model Flow Graphs
nondeterministic choice
1
2
Element
flow
flow
Procedure
Stop
Predicate
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Example FG instance

• ASG

• FG

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Trafo Def set of rules
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Graph formalism

• Graphs in this presentation
• flat (i.e., not hierarchical), untyped
• directed, edge-labelled, no parallel edges
• self-edges depicted as node labels
• Formally G (L,N,E) with
• L set of labels
• N finite set of nodes
• E ? N ? L ? N finite set of labelled edges
• Partial morphisms
• structure-preserving node mappings

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Graph Productions
(SPO Single Pushout Approach)
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Example production rule

• Alternative single-graph representation

green creator RHS, not LHSto be added
blue eraser LHS, not RHSto be matched and
deleted
black readerLHS and RHSto be matched and
preserved
red embargo NAC, not LHSforbidden
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Application scenario
Graph Production Systems
A-B Prod Syst
A-B Trafo

• Overhead Transformation to and from graphs
• Price for common representation
• Graph transformations inefficient
• Graph matching inherently complex (NP-complete)
• Domain-specific transformations superior
• Graph Trafo can serve as specification

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Graphs everywhere

• Other modelling domains (meta-models)
• XSD/XML
• ERD schemas/databases
• Class/object diagrams
• Certain patterns emerge
• Commonalities among modelling domains
• Should be formulated on MOF level

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Practice What is available?

• BOTL (München)
• Bidirectional O-o Transformation Language
• Transforms object models to object models
• FuJaBA (Paderborn, Kassel)
• From UML to Java and Back Again
• Generates Java code from enriched activity
  diagrams
• ATOM3 (Madrid)
• A Tool for Multi-Formalism Meta-Modelling
• Transforms any model at any meta-level

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Next step Dynamic Semantics

• Current research mostly on static semantics
• Models Class diagrams, ERD schemes, XML schemas
• Instances Objects, ER databases, XML documents
• Dynamic semantics how do systems behave?
• Can be expressed as changes on instance level
• These can also be seen as transformations
• Graph transformations for operational semantics
• Aim Semantics-preserving model transformations
• NWO project GRASLAND
• Graphs for Software Language Definition
• Aim Generic semantic definition language

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TAAL Experiment

• Kleppe, Rensink, Kastenberg
• Example O-Olanguage
• Transformations

GROOVE
ASG to FG
dynamic semantics
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Final words

• MDA Cool idea
• Good intuitions
• Poor mathematical backing
• Graph transformation Promising approach
• Good mathematical backing
• Useful for formalizing principles
• Questionable for practical transformations
• State of the art
• A lot of work at the stage of (small) case
  studies
• We need engineering discipline(Whos going to
  write the XSD meta-model in MOF?)