Using higher-order logic for modular specification of real-time distributed systems

Abstract

The problem of specifying and verifying modular components of real-time distributed systems is investigated, and a theory for a distributed real-time logic (DRTL), based on Jahanian and Mok's RTL, is presented. DRTL is proposed as a good basis in which to express the semantics of higher level specification languages.In looking for a method for composing specifications written in DRTL an analogy is found in Gordon's method for the specification of digital circuits, in which predicates are used to represent devices and higher-order logic is used for composition and proof. A signal on a wire, represented by a function of time, is taken to be analogous to a stream of event occurrences, represented by function that gives the time of the ith occurrence. A difference from hardware design, however, is the fact that event occurrence streams, unlike wires, are typed and there are some fundamental restrictions on how they can be combined in a specification. Another difference from hardware design is that real-time components cannot be composed quite so freely as with digital devices.A requirements language and a design language have been developed to express specifications for real-time distributed systems based on a programming environment using message-passing and processes. These languages are not discussed, but the expression of their semantics in DRTL is presented as an example of how component predicate specification can be combined with DRTL to produce modular specifications. Extensions to allow functional, as well as temporal, specification are briefly discussed.KeywordsEvent FunctionNotification EventNaming ConventionInput EventPhysical NodeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.