A formal language CCSL is introduced for describing specifications of classes in object-oriented languages. We show how class specifications in CCSL can be translated into higher order logic. This allows us to reason about these specifications. In particular, it allows us (1) to describe (various) implementations of a particular class specification, (2) to develop the logical theory of a specific class specification, and (3) to establish refinements between two class specifications. We use the (dependently typed) higher order logic of the proof-assistant PUS, so that we have extensive tool support for reasoning about class specifications. Moreover, we describe our own front-end tool to PVS, which generates from CCSL class specifications appropriate PVS theories and proofs of some elementary results.

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WC present the first results of a project called LOOP, on formal methods for the object-oriented language Java. It aims at verification of program properties, with support of modern tools. We use our own front-end tool (which is still partly under construction) for translating Java classes into higher order logic, and a back-end theorem prover (namely PVS, developed at SRI) for reasoning.In several examples we demonstrate how non-trivial properties of Java programs and classes can be proven following this two-step approach.