Successful software developers have long recognized that proper modeling is a key element to the development process that leads to creating robust software. For the past decade, the Object Constraint Language has offered a more precise (but not very popular) means of expressing a software design -- more precise than even the Unified Modeling Language. The growing acceptance of the Model-Driven Architecture (MDA) approach, and the significant changes to the UML 2.0 standard have placed the OCL near the forefront of object-oriented application development. The OCL no longer represents a level of detail that practitioners are likely to ignore. The OCL is now closely tied to both the UML 2.0 and MDA standardization initiatives. This closeness is certain to lead to an increased level of popularity in this precision language for modeling. This book, from the creators of the language, explains how software professionals can use the OCL to create better software.