A Module Language for Typing SIGNAL Programs by Contracts

Chapter 5, on "A Module Language for Typing SIGNAL Programs by Contracts", brings up the polychronous model of computation to present a means to modularly and compositionally support assumption-guarantee reasoning in that framework. Contract-based design has become a popular reasoning concept in which contracts are used to negotiate the correctness of assumptions made on th definition of a component at the point where it is used and provides guarantees to its environment. The chapter first elaborates formal foundations by defining a Boolean algebra of contracts in a trace-theoretical framework. Based on that contracts algebra, a general-purpose module language is then specified. The algebra and module system are instantiated to the framework of the synchronous data-flow language Signal. This presentation is illustrated with the specification of a protocol for Loosely Time-Triggered Architectures (LTTA)