ITU - MDD – Model-to-Model Transformations

L0082 - 2010-11-18

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ITU - MDD – Model-to-Model Transformations

This presentation describes the use Model-to-Model transformations (M2M). It focus on the why, what and how.

This presentation is developed for MDD 2010 course at ITU, Denmark.

Some materials by Artur Boronat, University of Leicester (UK) and Emilio Insfrán, TU Valencia (Spain) with permissions.

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What is Model-to-Model Transformations

Two kinds of model transformation: Model-to-Text transformation (M2T) Model-to-Model transformation (M2M)

A Model-to-Model transformation is the automated creation of m target models from n source models

Each model conforms to a given reference model (which can be the same for several models)

M2MM2M

M2TM2T

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Why use Model-to-Model Transformations

Translation

Refactoring

Refinement

Code Generation

Specialization

Migration

Normalization

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Model-to-Model Transformations Principles

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M2

M1

relational schema (model)

class diagram metamodel specification (CD) relational metamodel specification (RDBS)

conforms to

conforms to

context ForeignKeyinv: self.owningTable.columns -> includesAll( self.columns)

context AssociationEndinv: not(self.opposite.oclIsUndefined) implies (self.type=self.opposite.owningClass and

self.owningClass=self.opposite.type)inv: (lower = 0 or lower = 1) and (upper = 1 or upper = -1)

class diagram model (cd)

Example of Model Transformation

M2

M1

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Example of Model Transformation

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Approaches for Model Transformations

Model-to-model Model transformations are based on rules. These rules map constructs in the source model to

constructs in the target model

Meta-model A Meta-model B

Model A Model B

Transformation

Apply Transformation

conformsToconformsTo based onbased on

input output

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Some Terms

Endogeneous

Exogeneous

Horizontal

ve

rtica

l

M2

M1

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Combining both approaches in an MDE process

Application on a concrete use case: UML2 to Java

An M2T solution

A single transformation performing at the same time:

Refactoring (e.g. delete of multiple inheritance)

Mapping (UML2 concepts to Java concepts)

Extraction to a concrete syntax (conforming to the Java grammar)

MDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2 C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T Transformation

MDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2 C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T Transformation

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Same case using an M2M+M2T solutionMDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

MDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

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Same case using an M2M+M2T solution + new refactoringMDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2

C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

UML class

diagram

C2

refactoring

M2M

MDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2

C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

UML class

diagram

C2

refactoring

M2M

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Application on a concrete use case: UML2 to Java and C#

Same case using an M2M+M2T solution + new mappingMDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

C#grammar

C2

C# program

C2

M2T

extraction

C# program

C#

C2

C2

MDE Text

UML2

MOFEBNF

grammar

Javagrammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

C#grammar

C2

C# program

C2

M2T

extraction

C# program

C#

C2

C2

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Same case using an M2M+M2T solution + new extractionMDE Text

UML2

MOFEBNF

grammar

Java 1.6grammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

Java 1.4 grammar

C2

Java program

C2

MDE Text

UML2

MOFEBNF

grammar

Java 1.6grammar

C2C2

Java program

C2

UML class

diagram

C2

M3

M2

M1M2T UML

class diagram

Java program

Java

C2

C2

C2

refactoring mapping

M2MM2M

extraction

Java 1.4 grammar

C2

Java program

C2

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Advantages of such a generic M2M+M2T solution

Modularity Clearly separate the concerns (refactoring, mapping, extraction to a

given syntax, etc) Extensibility

Easily add new features (additional refactoring, different mapping, other extraction to a textual or graphical syntax, etc)

Reusability Apply the same feature in different contexts (i.e., the same refactoring

for targeting different languages) Homogeneity

Handle mostly models (extraction is just the final step) Abstraction

Focus is set only on the concepts (abstract syntax) and not on their various possible representations (concrete syntaxes)

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Important Success Factors for Model-to-Model Technologies

Ease of use It is likely not going to be the primary tool of any developer

Requirements on source and target models Form and format (text, XML, graph, …)

Traceability Can you trace changes in the input to changes in the final results Very important for certain industries

Reasoning about the transformation themselves Termination, Completeness, etc

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Several Types of Transformation Technologies

Text based model Using sed, awk, perl, Snobol… Data often represented as a text files

Tree based model Using XSLT Difficulties with models that’s are not pure trees Data often represented as simple XML files

Graph based model Using QVT, ATL, XTend, … Data often represented as XMI files

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General Purpose Languages

Java, VB, C# (take your favourite poison)

Rules are implemented from scratch

Depending on the form of the model you can have APIs to access the data Example: JMI or EMF (MOF-compliant Java Interfaces)

No overhead to learn a new language The programming complexity problem continues

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Text Manipulation Tools

Unix “pipe-line” tools sed, awk, perl, ….

Special purpose programming languages Snobol

Rules are typically based on regular expressions

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Extensible Stylesheet Language Transformation (XSLT)

XML-based language used for the transformation of XML documents Part of a W3C family of languages (XSL)

Describes how to format and transform XML files XSLT, XSL-FO, XPath

Used to model transformation Where models are in XMI encoding format

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Metamodels are provided as XML schemas (XSD or DTD) Models are represented as XML documents

XSLT Characteristics Declarative rather than imperative Consist of a template rules collection Each rule specifies what to add to a target fragment

Based on a source fragment and a fixed algorithm XSLT processor scan the source tree, apply rules and generate the target

tree Syntactical & inefficient for model transformations

XML (XMI) is verbose Operates on tree structures More batch than interactive Parameters passed by value

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XMLDocument 1

XMLSDocument 1

Valid

XSLTDocument

XSLTEngine

SourceSchema

FragmentMatchingPatterns

XMLDocument 2

XMLSDocument 2

Valid

TargetSchema

FragmentInsertion Actions

MatchedSource Fragments


Transformation process: Source document matching patterns XSLT document specifying actions that copy matched elements and

attributes from source document and assemble them Target document matching transformations

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<model xmlns:uml="http://www.eclipse.org/uml2/1.0.0/UML" xmlns:xmi="http://www.omg.org/XMI"> <package id="pck1" name=“library"> <class id="c1" name="Book"> <association aggregationType="composite" id="c1_ass1" name="chapters" targetClass="c2"/> <attribute id="c1_atr1" name="title" type="dt1"/> </class> <class id="c2" name="Chapter"> <attribute id="c2_atr1" name="nbPages" type="dt2"/> <attribute id="c2_atr2" name="title" type="dt2"/> <attribute id="c2_atr3" name="author" type="dt1"/> <association aggregationType="none" id="c2_ass1" name="book"

targetClass="c1"/> </class> </package></model>


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<model xmlns:uml="http://www.eclipse.org/uml2/1.0.0/UML" xmlns:xmi="http://www.omg.org/XMI"> <package id="pck1" name=“library"> <class id="c1" name="Publication"> <attribute id="c1_atr1" name="title" type="dt1"/> <attribute id="c1_atr2" name="nbPages" type="dt2"/> <attribute id="c1_atr3" name="authors" type="dt1"/> </class> <datatype id="dt1" name="String"/> <datatype id="dt2" name="Integer"/> </package></model>


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<?xml version="1.0" encoding="UTF-8"?><xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" > <xsl:output method="xml" /> <xsl:template match="library.Book" > <xsl:variable name="title" select="@title" /> <xsl:variable name="authors" select="concat(@chapters.author, ',')"/> <xsl:variable name="nbPages" select="sum(@chapters.nbPages)"/>

<xsl:call-template name="createPublication"> <xsl:with-param name="title" select="$title"/> <xsl:with-param name="authors" select="$authors"/> < xsl:with-param name="nbPages" select="$nbPages"/> </xsl:call-template> </xsl:template></xsl:transform>


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Graph Transformations

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Graph Transformations

Basic Operation: Match a set of nodes in the source graph

Transform matched data

Output nodes to the target graph

Some basic problems Graphs are not directed acyclic graphs (DAGs) so there can be multiple

references to the same nodes

How to you prevent the rules from matching the same data multiple times

How to handle inheritance for nodes – especially the nodes in the target model

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Book Chapter

nbPages : Integer

author : String

chapters

*

ElementWithTitle

title : String

RHSt : ElementWithTitleLHS

The pattern matches all nodes of type ElementWithTitle, considering the inheritance hierarchy

Type graph

Production rule

Inheritance

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Tree versus Graphs Transformations

XSLT

Operates on tree structures

Data conversion

XPath to traverse documents

XML based commands: transformation definitions tend to be quite verbose, low level of detail

Available in many platforms (libraries)

Graph transformations

Operates on graphs

Models without containments

Graph patterns

Graphical approach: large patterns can be difficult to draw

Higher conceptual level: inheritance, dangling edges, pattern matching

Formal approach: reasoning about termination and confluence, model checking

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QVT

QVT stands for Query/Views/Transformations OMG standard language for expressing queries, views, and transformations on

MOF models

Three language: Core, Relational and Operational

QVT is standards based language OMG QVT Request for Proposals (QVT RFP, ad/02-04-10) issued in 2002 Seven initial submissions that converged to a common proposal Current status (June, 2006): final adopted specification, OMG document

ptc/05-11-01

Automatic handling of traceability links

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Requirements for QVT Language

Some requirements formulated in the QVT RFP

Mandatory requirements

Query language Proposals shall define a language for querying models

Transformation language Proposals shall define a language for transformation definitions

Abstract syntax The abstract syntax of the QVT languages shall be described as MOF 2.0 metamodel

Paradigm The transformation definition language shall be declarative

Input and output All the mechanisms defined by proposals shall operate on models instances of MOF 2.0 metamodels

Optional requirements

Directionality Proposals may support transformation definitions that can be executed in two directions

Traceability Proposals may support traceability between source and target model elements

Reusability Proposals may support mechanisms for reuse of transformation definitions

Model update Proposals may support execution of transformations that update an existing model

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QVT – Relations and Core Languages

Relations Language A declarative specification of the relationships between MOF models Supports complex object pattern matching, and implicitly creates trace

classes and their instances to record what occurred during a transformation execution.

Core Language A small model/language which only supports pattern matching over a flat

set of variables by evaluating conditions over those variables against a set of models

It is equally powerful to the Relations language, and because of its relative simplicity, its semantics can be defined more simply, although transformation descriptions are more verbose

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QVT Relations – When and Where Clauses

when clause: conditions under which the relationship needs to hold. The relation ClassToTable needs to hold only when the PackageToSchema relation holds between the package containing the class and the schema containing the table.

where clause: condition that must be satisfied by all model elements participating in the relation, and it may constrain any of the variables in the relation and its domains.

when and where clauses may contain also any arbitrary OCL expressions

relation ClassToTable /* map each persistent class to a table */{ domain uml c:Class { namespace = p:Package {}, kind='Persistent', name=cn }

domain rdbms t:Table { schema = s:Schema {}, name=cn, column = cl:Column { name=cn+'_tid', type='NUMBER'}, primaryKey = k:PrimaryKey { name=cn+'_pk', column=cl} } when { PackageToSchema(p, s); } where { AttributeToColumn(c, t); }}

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Operational QVT

Operational == Procedural Uses OCL as procedural language

Needed when there are big differences between the input and output models Very difficult to map multiple source nodes to multiple target nodes in

Declarative languages Likewise difficult to handle shared nodes

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Operational QVT Example

Flattening UML class hierarchies: given a source UML model transform it to another UML model in which only the leaf classes (classes not extended by other classes) in inheritance hierarchies are kept.

Rules: Transform only the leaf classes in the

source model Include the inherited attributes and

associations Attributes with the same name override

the inherited attributes Copy the primitive types

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Operational QVT Example: Input Model

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Operational QVT Example: Expected Output Model

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Operational QVT Example: Expected Output Model

transformation SimpleUML2FlattenSimpleUML(in source : SimpleUML, out target : SimpleUML);main() { source.objectsOfType(Class)->map leafClass2Class(source); }

mapping Class::leafClass2Class(in model : Model) : Classwhen {not model.allInstances(Generalization)->exists(g | g.general = self)} {

name:= self.name; abstract:= self.abstract; attributes:= self.derivedAttributes()->map property2property(self)->asOrderedSet();}

mapping Property::property2property(in ownerClass : Class) : Property { name:= self.name; type:= self.type; owner:= ownerClass;}

query Class::derivedAttributes() : OrderedSet(Property){ if self.generalizations->isEmpty() then self.attributes else self.attributes->union( self.generalizations->collect(g | g.general.derivedAttributes()->select(attr | not self.attributes->exists(att | att.name = attr.name) ) )->flatten() )->asOrderedSet() endif}

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ATL – Atlas Transformation Language

ATL is the ATLAS INRIA & LINA research group answer to the OMG MOF/QVT mix of declarative and imperative constructs expression language based on OCL 2.0 supports queries, views and transformations described by a MOF metamodel and a textual concrete syntax

ATL transformations: are defined via the

correspondingMOF based metamodels

are not bidirectional ATL has become a reference

language for model transformations and it is now part of the Eclipse Modeling Project

MetamodelA MetamodelB

ModelA ModelB

MOF

ATL

defines

M1

M0

M2 ATL Transformation

Model Transformation

conforms to

conforms to

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ATL Example

Assume we want to translate data from a hierarchical model (Family) to a flat model (Person)

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ATL Example

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ATL Example

module Families2Persons;

-- @path Families=/Families2Persons/Families.ecore-- @path Persons=/Families2Persons/Persons.ecore

create OUT: Persons from IN: Families;

rule Member2Male {from

s: Families!Member (not s.isFemale())to

t: Persons!Male (fullName <- s.firstName + ' ' + s.familyName

)}

rule Member2Female {from

s: Families!Member (s.isFemale())to

t: Persons!Female (fullName <- s.firstName + ' ' + s.familyName

)}

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ATL Example

helper context Families!Member def: isFemale(): Boolean =if not self.familyMother.oclIsUndefined() then

trueelse

if not self.familyDaughter.oclIsUndefined() thentrue

elsefalse

endifendif;

helper context Families!Member def: familyName: String =if not self.familyFather.oclIsUndefined() then

self.familyFather.lastNameelse

if not self.familyMother.oclIsUndefined() thenself.familyMother.lastName

elseif not self.familySon.oclIsUndefined() then

self.familySon.lastNameelse

self.familyDaughter.lastNameendif

endifendif;

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More Information

“QVT Repository” http://www.toodoc.com/qvt-pdf.html

Repository with many QVT documents “MOF QVT Final Adopted Specification”

http://www.omg.org/docs/ptc/05-11-01.pdf You usual very hard to read OMG model

http://www.toodoc.com/qvt-pdf.html

http://www.omg.org/docs/ptc/05-11-01.pdf

ITU - MDD – Model-to-Model Transformations

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