Preface and Introduction


In November 1997, the Object Management Group (OMG) set a standard for object-oriented analysis and design facilities. The standard, known as the Unified Modeling Language (UML), includes model diagrams, their semantics, and an interchange format between CASE tools. Within UML, the Object Constraint Language (OCL) is the standard for specifying expressions that add vital information to object-oriented models and other object modeling artifacts.

In UML version 1.1, this information was thought to be limited to constraints, where a constraint is defined as a restriction on one or more values of (part of) an object-oriented model or system. In UML version 2, the understanding is that far more additional information should be included in a model than constraints alone. Defining queries, referencing values, or stating conditions and business rules in a model are all done by writing expressions, i.e., these are all expressed in OCL.

OCL evolved from an expression language in the Syntropy method through a business modeling language used within IBM until it was included in UML in 1997. At that point in time, it received its current name. This name is now well established, so it would not be expedient to change it to, for instance, Object Expression Language , although this name would currently be more appropriate.

OCL has been used as an expression language for object-oriented modeling during the last six years . Today, a large number of tools support the language. Since OCL was first conceived, there have been many changes and additions to the language. Lately, this has led to a new version of OCL, version 2, to accompany the new version of UML. OCL version 2 is formally defined in the Object Constraint Language Specification [OCL03]. This book explains all features of this version of OCL.

Recently, the OMG has launched an initiative called the Model Driven Architecture (MDA). The essence of the MDA approach is that models form the basis of software development. In order to work with this architecture one needs good, solid, consistent, and coherent models. Using the combination of UML and OCL, you can build such models.

In the many books that have been published on the subject of UML, its expression language has not received the attention it deserves . The first aim of this book is to fill this gap and to explain UML's expression language, which supports the task of modeling object-oriented software as much as the UML diagrams. The second aim of this book is to introduce OCL version 2 to a wider audience. Not everyone is pleased with reading a formal standard; the information should be available in a more accessible form. The last aim of this book is to explain why using OCL is essential to the application of MDA. Without OCL and the languages, transformations, and so on that are all enabled by OCL, application of the MDA is bound to fail.



Object Constraint Language, The. Getting Your Models Ready for MDA
The Object Constraint Language: Getting Your Models Ready for MDA (2nd Edition)
ISBN: 0321179366
EAN: 2147483647
Year: 2003
Pages: 137

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net