Employing the Object Constraint Language in Model-Based Engineering

MBE (Model-Based Engineering) proposes to develop software by taking advantage of models, in contrast to traditional codecentric development approaches. If models play a central role in development, model properties must be formulated and checked early on the modeling level, not late on the implementation level. We discuss how to validate and verify model properties in the context of modeling languages like the UML (Unified Modeling Language) combined with textual restrictions formulated in the OCL (Object Constraint Language). Typical modeling and transformation languages like UML (Unified Modeling Language), EMF (Eclipse Modeling Framework), QVT (Queries, Views, and Transformations) or ATL (Atlan Transformation Language) are complemented by the textual OCL (Object Constraint Language) enriching graphical or textual models with necessary details. Models allow the developer to formulate essential system properties in an implementationand platform-independent way. Precise object-oriented development must take into account system structure and system behavior. The system structure is often captured by class diagrams and can be instantiated in terms of prototypical exemplars by object diagrams. The system behavior can be determined by statechart diagrams, and system execution traces can be demonstrated by sequence diagrams. OCL restricts the possible system states and transitions through the use of class invariants, operation preand postconditions, state invariants, and transition preand postconditions. OCL can also be used during model development as a query language. Modeling features and their analysis through validation and verification must be supported by tools like, for example, the tool USE (UML-based Specification Environment) [1]. Within USE, UML class, object, statechart, and sequence diagrams extended with OCL are available [2]. OCL has been extended with programming language features in SOIL (Simple Ocl-like Imperative Language) which allows the developer to build operation realizations on the modeling level without having to dig into implementation level details [3]. Thus models in USE are executable, but a prescriptive SOIL model for operations can be checked against descriptive plain OCL preand postconditions. Tools like USE assist the developer in order to validate and to verify model characteristics. Validation and verification can be realized, in USE for example, by employing a so-called model validator based on relational logic and SMT