Combining algebraic and predicative specifications in Larch
Recently there has been a great deal of theoretical interest in formal specifications. However, there has not been a corresponding increase in their use for software development. Meanwhile, there has been significant convergence among formal specification methods intended for practical use.
The Larch Project is developing tools and techniques intended to aid in the productive use of formal specifications. This talk presents the combination of ideas, both old and new, that we are currently exploring.
One reason why our previous specification methods were not very successful was that we tried to make a single language serve too many purposes. To focus the Larch Project, we made some fairly strong assumptions about the problem we were addressing.
Each Larch specification has two parts, written in different languages. Larch interface languages are used to specify program units (e.g., procedures, modules, types). Their semantics is given by translation to predicate calculus. Abstractions appearing in interface specifications are themselves specified algebraically, using the Larch Shared Language.
A series of examples will be used to illustrate the use of the Larch Shared Language and the Larch/CLU interface language. The talk will conclude with notes on the key design choices for each of the languages, and for the method of combining the two parts of a specification.
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