Current research in specifications is emphasizing the practical use of formal specifications in program design. One way to encourage their use in practice is to provide specification languages that are accessible to both designers and programmers. With this goal in mind, the Larch family of formal specification languages has evolved to support a two-tiered approach to writing specifications. This approach separates the specification of state transformations and programming language dependen-cies from the specification of underlying abstractions. Thus, each member of the Larch family has a subset derived from a programming language and another subset independent of any programming languages. We call the former interface languages, and the latter the Larch Shared Language. This paper focuses on Larch interface language specifications. Through examples, we illustrate some salient features of Larch/CLU, a Larch interface language for the programming language CLU. We give an example of writing an interface specification following the two-tiered approach and discuss in detail issues involved in writing interface specifications and their interaction with their Shared Language components.

This thesis investigates a particular approach, called state-transition specification, to the problem of describing the behavior of modules in a distributed or concurrent computer ,stem. A state-transition specification consists off (1) a state machine, which incorporates the safety or invariance properties of the module, and (2) validity conditions on the computations of the machine, which'capture the desired liveness or eventu;lity properties. The theory and techniques of state. transition specification are developed'from first principles to a point at which it is possible to write example sPeCificatiOns,'to check-the Specifications for coraiatency, and to perform correctlse examples.