Stochastic Reasoning About Channel-Based Component Connectors

Constraint automata have been used as an operational model for component connectors that coordinate the cooperation and communication of the components by means of a network of channels. In this paper, we introduce a variant of constraint automata (called continuous-time constraint automata) that allows us to specify time-dependent stochastic assumptions about the channel connections or the component interfaces, such as the arrival rates of communication requests, the average delay of enabled I/O-operations at the channel ends or the stochastic duration of internal computations. This yields the basis for a performance analysis of channel-based coordination mechanisms. We focus on compositional reasoning and discuss several bisimulation relations on continuous-time constraint automata. For this, we adapt notions of strong and weak bisimulation that have been introduced for similar stochastic models and introduce a new notion of weak bisimulation which abstracts away from invisible non-stochastic computations as well as the internal stochastic evolution.