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Model transformations

Paolo Ciancarini

Agenda
  Modeling platforms and Platform Independence
  Model Transformations
  MDA in the Eclipse IDE
  The Atlas Transformation Language

CIM, PIM and PSM

  CIM: Computation Independent Model
  A vocabulary of a problem domain useful to a
variety of stakeholders
  PIM: Platform Independent Model
  A specification of a system that does not take into
account technical details of a specific platform
  PSM: Platform Specific Model
  A specification of a system expressed in terms of
the specification model of the platform

The MDA process (abstraction)

www.ibm.com/developerworks/ibm/library/i-modev1/!

MDA process for a complex system

MDA: Mappings between Models

From PIM to Specific
Platform- Middleware
Independent Technologies via OMG
Model
Standard Mappings

CORBA Java/EJB XML/SOAP Other
Model Model Model Model
From PSM to
application interfaces,
code, GUI descriptors,
SQL queries, etc.
CORBA Java/EJB XML/SOAP Other

Model Representation

UML Model (PIM) XMI Document
<Auto>
<Color> Red </Color>
MOF
<Door> 4 </Door>
<Engine> 2 </Engine>
</Auto>

XMI DTD, Schema
IDL, Java… <!Element Auto
interface Auto (Color*,
{ Class Auto Door*,
}; {public String color; Engine*)>
public int Door;
public int Engine;
}

Model Transformation

  Working with interrelated models requires to ensure
their vertical, horizontal, and evolutionary consistency
  This activity can be performed taking one or more
source models as input and producing one or more
target models as output
  The process of model transformation must comply with
a set of transformation rules

PIM to PSM Transformation

  It is used when the PIM is mapped into
a platform specific infrastructure
  The transformation is based on a set of
platform features
  These features should be described by
UML

PIM to PIM Transformation

  It is used when models are enhanced,
refined or filtered during the
development lifecycle without needing
any platform specific information
  Example: analysis-to-design model
transformation

PSM to PSM Transformation

  It is used for component realization
and deployment
  Generally, it is related to platform
dependent model refinement

PSM to PIM Transformation

  It is performed for abstracting models of
existing technology-dependent
implementations into a platform independent
model
  It is a refactoring process hard to be fully
automated

Model Mapping
  A technique for setting the specifications, that drives
the transformation from the source model to the target
model
  The main mapping techniques are [8s]:
  Model-Type mapping
  The mapping is realized between platform-independent data types and platform-
specific data types. The two kinds of data type drive the transformation
  Metamodel mapping
  The mapping is realized between the PIM metamodel data type and the PSM
metamodel data type.
  Model-Instance mapping
  It uses marks, i.e. concepts of the target-model explaining how to transform source
model elements

Approaches to Model Transformations

  The tools performing model transformations can use:
  Direct transformations: internal model representation
manipulated by specific APIs
  Intermediate transformations: model exported in an
external standard form (e.g., XMI) that can be manipulated
  Transformation language: a language with specific
constructs for defining and applying transformations

Platform Independence
  Platform Independence is a “fuzzy” concept
  It means independence from a specific execution and
development domains
  The domains from which the independence can be
asserted are the usual software engineering
abstraction domains:
  Programming Languages

  Software Architectures

  Operative Systems

  Data Representation

Ex.: Bank Account Architectural PIM

•  Nothing said about the
architecture and the
developing technologies
•  It is the model used by bank
manager and stakeholders

Ex.: Bank Account Architectural PSM

•  It specifies a remote and some local objects
•  It adds some implementation information
•  It is the model used by analyst and
programmers

•  it conforms to the PIM
•  it can be a PIM for a further platform specific model

MDA Tools

  Currently, there are no tools that implement MDA
as envisioned by the OMG community
  MDA itself is still being defined
  Existing tools allow partial transformations
  They are usually limited to
  specific platforms
  specific languages
  specific transformations
  Usually they are evolutions of tools born in other
research fields
  Especially in Generative programming and
Metaprogramming

EMF and ATL
  Two interesting technologies are emerging that are
more and more used in MDA tools:
1.  The Eclipse Modeling Framework (EMF) is the
analogous of MOF in the Eclipse IDE Platform
  It consists of an extended set of API, a metamodelling
framework named Ecore and an Eclipse IDE plug-in
2.  The Atlas Transformation Language (ATL) is a
language specifically targeted for model
transformations
  It supports MOF 1.4 and Ecore while conforming to MDA
transformation specifications

MDA and Middleware
Middleware is an enabling
technology for MDA

Generators’
increasing
complexity

From Coding to Modeling

  What is the difference between programming
language abstractions and MDE/MDA
abstractions?
  The former allow to abstract the solution space
  they are “computing oriented”
  MDE/MDA allow to abstract the problem space
  they are “application domain oriented”
  The current Enterprise Computing scenario
requires to move the software development
emphasis from coding to modeling systems

Metadata Integration
  Why we cannot use a single language to describe all the
aspects of a system?

  The problem is not that we
use different languages to
describe different aspects of
software components
  The problem is that we have
no overall architecture for
integrating specifications
made in different languages
  MDA defines a single
architecture for the integrated
management of metadata

The Eclipse IDE in a Nutshell
  Eclipse is an open Universal Tooling Platform
  Open Source licensed via Common Public License
  Managed via the Eclipse Project (www.eclipse.org)
  Maintained by the Eclipse Foundation
  An independent consortium whose members include: IBM, SuSe,
Borland, RedHat, HP, SAP, OMG
  It provides an open platform for application
development tools
  It runs on a wide range of operating systems
  It is language-neutral
  It facilitates seamless tool integration
  It adds new tools to existing installed products

What is Eclipse?

  A general purpose IDE
  An open, extensible architecture based on plug-ins

Plug-in development environment PDE

Java development tools JDT

Eclipse Platform Platform

Standard Java2 Virtual Machine Java VM

The Eclipse Architecture
Another
Eclipse Platform
App

Java Workbench Help
Development
Tools JFace
(JDT)
SWT
Team Your
Tool/App

Plug-in Workspace
Development Debug
Environment
(PDE)

Their
Platform Runtime Tool

Eclipse Project

MDA in Eclipse
  There are a number of plug-ins that support
the MDA features in Eclipse
  Indeed, there is not a single tool that gives a
full support of MDA features as envisioned
by the OMG
  Three MDA plug-in categories can be
identified basing on their focus:
1.  Models representation and management
2.  Models transformation
3.  Models-to-Code generation

Notable MDA Projects in Eclipse
Name Description Categ./
License
Acceleo A MDA based code generator for various target middleware 3 / Free
and languages: Java EE, C#, Python, PHP etc.

Atlas It defines a management environment for MDE repositories 1 / Free
based on the "megamodel" approach. A megamodel is a
Megamodel registry of model resources available in a given scope (a
Management zone) In order to manage megamodels users may use
(AM3) metamodels from a library or invent their own ones for new
kinds of artifacts.
Atlas Model A tool for representing correspondence between models by 1 / Free
means of a model (named weaving model). Common
Weaver (AMW) weaving use cases are: data exchange, data integration,
model merging, etc
Atlas A model transformation language that provides 2 / Free
ways to produce a set of target models from a
Transformation set of source models. It also provide a toolkit
Language (ATL) (the ATL IDE) with a number of tools aimed to
ease the development of ATL transformations.


License
Epsilon It can be used to manage models of different modeling 1/Free
technologies using a family of integrated model
management languages. It can be used for model
navigation, modification, transformation, validation and
comparison. It also provides tools for defining and
executing wizard and for code profiling and monitoring.
IBM Model Is a set of tools that helps to make comparisons, check 2 / IBM
consistency, and implement transformations between License
Transformation Eclipse Modeling Framework (EMF) models.
Framework
Kermeta A metaprogramming environment based on an object 2 / Free
oriented executable meta-modeling paradigm: a
Domain Specific Language (DSL) optimized for
metamodel engineering. It allows model and metamodel
management, weaving and transformation.


License
openArchitectur It is suite of tools and components supporting in 1, 3 / Free
model driven software development. It is built upon a
eWare modular model-to-code generator framework
implemented in Java. It supports arbitrary import (model)
formats, meta models, and output (code) formats It is “a
tool for building MDA tools”
AndroMDA AndroMDA is an extensible generator framework that 3 / Free
adheres to MDA. Models from UML tools are
transformed into deployable components different
platforms: J2EE, Spring, .NET. It provides patterns for
Axis, Struts, JSF, Spring, Hibernate and other toolkits
QiQu It transforms an UML-model into source-code (Java, C#, 3 / Free
Cobol etc.). It relies on XMI and allows to build a
domain-specific generator that transform models into
code or anything else (XML, HTML, Scripts, Excel etc.)

Modeling Eclipse Plugins: http://www.eclipseplugincentral.com/Web_Links-index-req-viewcatlink-cid-11.html

MDA Enabling Technologies in Eclipse

  There are a set of de-facto standard Eclipse
plug-ins that enable MDE features
  These plug-ins enable upper-standing MDA
plug-ins to operate
  We consider an essential subset of these
plug-ins in order to start experiencing with
MDA

QVT (Query View Transform)

  QVT is an OMG specification
  QVT extends OCL 2.0 to imperative OCL
  QVT defines 3 DSL named Relations,
Core and Operational Mappings
  Relations and Core are declarative
languages
  OperationalMapping is an imperative
language with constructs like loops,
conditions, etc.

A Transformation Language: ATL
  The Atlas Transformation Language (ATL)
is an answer to the OMG Query View and
Transformation (QVT) RFP
  ATL is a QVT-like transformation language
and engine with a large user community and
an open source library of transformations
  ATL provides the developers with a mean to
specify the way to produce a number of
target models from a set of source models

Eclipse and Modeling Plug-ins

  The Eclipse Modeling Framework (EMF) is a
framework and a code generation facility
  It allows to define and mange models in Java,
XML and UML
  It relies on a meta-metamodel named Ecore
  UML2 is an EMF-based implementation of the
UML 2.x metamodel
  It provides the support for UML model plug-ins
  It defines a common XMI schema for diagram
interchange

Eclipse and Graphical Plug-ins
  The Graphical Editing Framework (GEF) allows
to create a graphical editor under Eclipse
  GEF provides a layout and rendering toolkit for
displaying graphs, manage palettes, handle and
resize graphical objects
  The Graphical Modeling Framework (GMF)
provides components and runtime
infrastructures for developing graphical editors
based on EMF and GEF
  reusable components for graphical editors
  generative infrastructure to graphical editor production

UML Modeler Plug-ins

Name Description
OmondoUML It is a visual modeling tool based on UML2. It supports
reverse engineering and production code for EJB,
Struts, Web Services. It is based on GEF and EMF.

Papyrus It is an open source product to model in UML2. It
allows to graphically represent diagrams in the
Diagram Interchange (DI2) OMG standard. It supports
Java and C++ code production and some UML
profiles (e.g. SysML)
Topcased It is a software engineering toolkit that provides
various modelers such as UML, Ecore, SysML. It is
compliant with the requirements of critical and
embedded applications
Eclipse ArgoUML It integrates the ArgoUML open source tool in the
Eclipse platform. It is a complete UML modeler
integrated with the AndroMDA MDA plug-in.

The ATLAS Transformation Language

  ATL is a model transformation language
  Specified both as a metamodel and as a textual concrete syntax
  It is both declarative and imperative
  declarative style is the default choice for simple transformations
  source model elements are navigated by means of a set of rules that
create target model elements
  It relies on a ATL Virtual Machine that allows transformations
  A transformation from the ATL metamodel to the VM code enables to
“execute” ATL transformations
  It has been implemented as an Eclipse plug-in

ATL Architecture
  Execution Engine
  Virtual Machine
  ATL to bytecode compiler
  Eclipse IDE used for
  Editor with syntax highlighting
  ATL launch support
  Source debug

ATL Mapping Technique
  The mapping technique used by ATL is
metamodel-based
MMM: MOF or Ecore [13]
MMt: ATL metamodel
Mt: ATL transformation model
MMa: source metamodel
MMb: target metamodel
Ma: source model
Mb: target model

Conforming to OMG Q/V/T specifications the transformations (Mt) are
defined as models as well conforming to the ATL metamodel (MMt)

ATL Transformations

  ATL allows to define different types of
transformations
  ATL Modules: are model to model
transformations
  ATL Queries: are model to primitive datatype
transformations
  ATL Libraries: factorize the ATL code in order
to be imported and used in multiple
transformations
  An ATL transformation file has the .atl
extension

ATL Modules

  Modules enable ATL developers to specify
  the way to produce a set of target models starting
from a set of source model
  Modules are structured in three sections:
  Header section that defines some attributes relative
to the transformation
  Helpers that are similar to Java methods
  Rules that define the way target models are
generated from source models

ATL Rules

  There are two different types of rules
  Matching Rules: for ATL declarative specifications
  to define for which kind of source elements target elements must
be generated
  to define the way the generated target elements have to be
initialized
  Called Rules: for ATL imperative programming
  they are a particular type of header that can generate target
model elements
  It has to be called from an imperative code section

ATL Execution Modes

  ATL defines two different execution modes for its modules:
  Normal execution Mode
  Explicitly specifies how each target model element must be generated
from source model elements
  Refinement execution Mode
  Source model elements are implicitly copied from the source to the
target model
  ATL developers focus on the generation of the modified target
elements
  It is limited to the transformation of a single source model to a single
target model conforming to the same metamodel

Source Meta-model

Simplified UML meta-model

Target Meta-model

Simplified Java meta-model

Transformation Rules
Transformation declaration and a transformation rule:

TRANSFORMATION uml2java(SOURCE UML, TARGET Java)!
TRACKING TModel;!

RULE umlClassifierToJavaClass(X, Y)!
FORALL UMLClassifier X!
WHERE X.name = N!
MAKE JavaClass Y,!
Y.name = N!
LINKING X, Y BY JavaClassFromUMLClassifier;!
...!

Tracking Relationships
Tracking class and a transformation rule:
CLASS JavaClassFromUMLClassifier {!
UMLClassifier a;!
JavaClass c;!
KEY (a);!
}!

RULE umlAttributeToJavaField!
FORALL UMLAttribute X!
WHERE JavaClassFromUMLClassifier LINKS X.owner, JC!
MAKE JavaField Y,!
Y.owner = JC!
LINKING X, Y BY FieldFromAttr;!

Rule Inheritance
Rule inheritance and Superseding:

CLASS JavaIntfFromUMLIntf EXTENDS JavaClassFromUMLClassifier;!

RULE umlInterfaceToJavaInterface(X, Y)!
SUPERSEDES umlClassifierToJavaClass(X, Y)!
FORALL UMLInterface X!
MAKE JavaInterface Y,!
Y.name = X.name!
LINKING X, Y BY JavaIntfFromUMLIntf;!

RULE umlClassToJavaClass(X, Y)!
EXTENDS umlClassifierToJavaClass(X, Y)!
MAKE JavaMethod M,!
M.name = X.name,!
Y.constructor = M!
LINKING X, M BY JavaConsFromUMLClass;!

ATL Syntax Essentials

  Header syntax
module module_name;
create (output_model:output_metamodel)+ [from | refines]
(input_model:imput_metamodel)+;

  Import syntax
uses extensionless_library_file_name;

  Helper syntax

helper context context_of_definition
def: (par_name: par_type) helper_code

ATL Syntax Essentials
  Matching Rule
rule rule_name {
from
source_pattern : source_metamodel!element
to
target_pattern : target_metamodel!element
(
[targt_entity <- source_pattern.source_entity]*
)
[do { imperative_code }]?
}
  Called Rule
rule rule_name ([param_name: paramType]){
[[to
target_pattern : target_metamodel!element
(
targt_entity <- local_variable
)]*| [do { imperative_code} ] *] ?
}

ATL DataTypes
  The ATL language is based on the OMG Object
Constraint Language (OCL)
  Primitive DataType
  Boolean, Integer, Real, String
  Collection DataType
  Set, OrderedSet, Sequence, Bag as collection_type
(element_datatype)
  Tuple DataType
  TupleType(var_name1 : var_type1, ..., var_namen :
var_typen)
  Map DataType
  Map{(key1, value1), ..., (keyn, valuen)}
  Model Element DataType
  metamodel!class

An ATL Transformation

The Author Source Metamodel The Person Target Metamodel

  The goal is a model to model PIM to PSM
transformation
  name and surname attributes must be preserved
  An instance of Author is mapped into an instance of
Person

An ATL Transformation
module Author2Person;
create OUT : Person from IN : Author;

rule Author {
from
a : Author!Author
to
p : Person!Person (
name <- a.name,
surname <- a.surname
)
}

Conclusion
MDE is the next step of the object technology
  As objects and classes were seen in the 80's as "first class
entities", with libraries of several hundred of classes
hierarchically organized, models and metamodels are
beginning to be considered alike in the 2000's
  Libraries (lattices) of hundreds of metamodels of high
abstraction and low granularity are beginning to appear.
Each such metamodel may contains several hundreds of
concepts and relations
  Tools are needed to work with these libraries of models and
metamodels
  Research is needed to bring together theory and practice of
model engineering (ontologists, methodologists, software
practitioners, information system builders, database
specialists, etc.)

Self-test questions

  What is a model transformation?
  What is the goal of model
transformations?
  What is QVT?
  What is ATL?

References
Bézivin: On the unification power of models. Software and
System Modeling, Springer, 4:2(171-188), May 2005
Frankel, Model Driven Architecture: Applying MDA to
Enterprise Computing, Wiley, 2003
Kurtev, Bezivin, Jouault, Valduriez, “Model-Based DSL
Framework” . ACM OOPSLA, 602—616. 2006.
Mellor, Scott, Uhl, Weise MDA Distilled: Principles of
Model-Driven Architecture, Addison-Wesley, 2004
Schmidt, Model-Driven Engineering. IEEE Computer, 39:2
(25-31), February 2006.

Specifications and URLs
[1s] Eclipse ATL Project, http://www.eclipse.org/m2m/atl
[2s] Eclipse EMF Project, http://www.eclipse.org/modeling/emf/
[3s] OMG, “Common Warehouse Meta-model (CWM)”, Version 1.0, October
2001, http://www.omg.org/cgi-bin/doc?formal/01-10-01.pdf
[4s] OMG, “XML Metadata Interchange (XMI) Specification v1.2”, January
[5s] OMG, “Meta Object Facility (MOF) Specification”, Version 1.4, OMG, April
[6s] OMG, “Meta Object Facility (MOF) Core Specification”, Version 2.0,
January 2006, http://www.omg.org/docs/formal/06-01-01.pdf
[7s] OMG, “Meta Object Facility 2.0 Query/View/Transformation Specification”,
November 2005, http://www.omg.org/docs/ptc/05-11-01.pdf
[8s] OMG, “MDA Guide Version 1.0.1”, June 2003,
http://www.omg.org/docs/omg/03-06-01.pdf
[9s] OMG, “Unified Modeling Language (UML), version 1.4”,
September 2001, http://www.omg.org/cgi-bin/doc?formal/01-09-67
[10s] OMG, “Unified Modeling Language: Infrastucture”, version 2.2.1,
February 2007, http://www.omg.org/docs/formal/07-02-04.pdf
[11s] Sun, “Java Metadata Interface (JMI) API 1.0 Specification”,
http://jcp.org/aboutJava/communityprocess/final/jsr040/index.html

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