JAVA/A Component Model

The JAVA/A approach aims at semantically well-founded and coherent modelling and programming concepts for components: based on sound theoretical foundations it enhances the widely used UML 2.0 component model by modular analysis and verification techniques and a Java-based architectural programming language. Our JAVA/A component model is inspired by ideas from “Real-Time Object Oriented Modeling” (ROOM [1]): components are strongly encapsulated behaviours and any interaction of components with their environment is regulated by ports. We took up the ROOMmodel in its version integrated into the “Unified Modeling Language 2.0” (UML 2.0 [2]), though in a simplified form which, however, keeps the main structuring mechanisms and focuses on strong encapsulation as well as hierarchical composition. In [3], we devised an algebraic semantic framework for this model; furthermore, we introduced an “architectural programming” language, JAVA/A, which allows programmers to represent software architectures directly in the implementation language and thus helps to prevent “architectural erosion” [4]. In contrast to interface-based component approaches (like COM, CORBA, Koala, KobrA, SOFA; see [5] for an overview), the primary distinguishing feature of ROOM, and hence of the JAVA/A component model, is the consistent use of ports as explicit architectural modelling elements. Ports allow designers to segment the communication interface of components and thus, in particular, the representation of different “faces” to other components. Moreover, ports are equipped with behavioural protocols regulating message exchanges according to a particular viewpoint. Similar to JAVA/A, ArchJava [6] and ComponentJ [7] are architectural programming languages which integrate