Chapter 5 Component Coordination in

Modeling is an essential part of large software projects. The Unified Modeling Language (UML) has become the de-facto standard language for specifying, modeling and documenting software systems, visualizing software systems. The basic innovative ideas of UML, which are the main reasons for its popularity, are the unification of the concepts and notations used in the life-cycle of software development as well as the recognition of the importance of modeling and analysis as a means to improve quality. UML consists of a number of diagrams used for expressing the goals of the system (use case diagrams), for specifying the structure of the system (class diagrams) and the behavior of the system (state diagrams, activity diagrams, sequence diagrams). In this paper we introduce a formal model of components in UML. This model has been developed in the context of the European IST project OMEGA. The aim of this project is the correct development of real-time embedded systems based on formal techniques. The approach followed is based on a formal semantics of a suitable subset of UML which includes class and state diagrams, a version of the Object Constraint Language, use case diagrams, and live sequence charts (an extension of UML’s sequence