Linking Programs to Architectures: An Object-Oriented Hierarchical Software Model Based on Boxes

Modeling software systems has several purposes. The model provides a communication means between developers, a backbone to specify and check properties of the system, and a structure to organize, explain, and develop the implementation of the system. The focus of our approach is to address these purposes for hierarchically structured, object-oriented software systems. The hierarchical structure refers to the component instances at runtime: a runtime component may consist of a dynamically changing number of objects and other runtime components. Our modeling technique builds on and extends the concepts of class-based object-oriented languages. Runtime components are created by instantiating box classes. The modeling technique provides ports to tame object references and aliasing and to decouple components from their environment. It supports dynamic linkage, i.e. ports can be connected and disconnected at runtime. The used concurrency model is based on the join calculus. Hierarchical software models allow to structure a system into components of different sizes where large components are recursively built from smaller ones. Dynamic linkage enables modeling of client–server behavior and open systems. For such systems, it is more difficult to separate the typical architectural level that deals with components and connectors and the realization level that describes the internals of components. The reasons are: