Interaction interfaces-towards a scientific foundation of a methodological usage of message sequence charts

We introduce the formal notion of an interaction interface. Its purpose is to specify formally the interaction between two or more components that co-operate as subsystems of a distributed system. We suggest the use of interaction interfaces for the description not of the behaviour of a single component in isolation but of the interface, the co-operation, between two or more components that are interacting within a distributed system. Typical examples are the interaction between an embedded system and its environment or the interaction between a sender and a receiver in a communication protocol. An interaction interface can be formally described by predicates characterising sets of interaction histories. We understand the specification of interaction histories as a typical step in system development that prepares the decomposition of a system into interacting subcomponents. After fixing the distribution structure of the system, an interaction interface is worked out that describes how the introduced subcomponents interact. In a successive development step we systematically derive the individual component specifications from the interface description. We show how such an interaction interface can be decomposed systematically into component specifications