Protective Interface Specifications

Authors: Gary Leavens and Jeannette M. Wing

to appear in Proceedings of TAPSOFT '97

The full text of this paper (in PostScript).


The interface specification of a procedure describes the procedure's behavior using pre- and postconditions. These pre- and postconditions are written using various functions. If some of these functions are partial, or underspecified, then the procedure specification may not be well-defined.

We show how to write pre- and postcondition specifications that avoid such problems, by having the precondition ``protect'' the postcondition from the effects of partiality and underspecification. We formalize the notion of protection from partiality in the context of specification languages like VDM-SL and COLD-K. We also formalize the notion of protection from underspecification for the Larch family of specification languages, and for Larch show how one can prove that a procedure specification is protected from the effects of underspecification.

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