Analytic Real-Time Interfaces for state-based Components

Interface theories provide the foundation for formally defining and exploiting often implicitly made assumptions about the environment a component is interacting with. This paper develops a procedure for computing analytic input/output bounds for event streams consumed/emitted by the individual components of a system design, allowing to define state-less assume/guarantee (A/G) realtime interfaces for each component. However, contrary to existing work this paper extends interface definitions with properties to be met invariantly by any component that implements it. This allows to compute bounds of key performance metrics of the overall system design by solely considering the information provided by the enriched interfaces. This is important as it supports incremental, i. e. component-wise evolution of system designs for the following reason: given a consistent interface-based system description the interface-derived properties are invariant w. r. t. composition and substitution of components, as long as each state-based component implementation is conformant to its interface and the interfaces are compatible. This paper establishs the required consistency and conformance criteria and develops the machinery for carrying out the checks in an automatic fashion. Thereby it advocates a strictly compositional design approach and improves the scalability of statebased analysis methods.