. We present a semantic representation of the core concepts of the specification language Z in higher-order logic. Although it is a "shallow embedding" like the one presented by Bowen and Gordon, our representation preserves the structure of a Z specification and avoids expanding Z schemas. The representation is implemented in the higherorder logic instance of the generic theorem prover Isabelle. Its parser can convert the concrete syntax of Z schemas into their semantic representation and thus spare users from having to deal with the representation explicitly. Our representation essentially conforms with the latest draft of the Z standard and may give both a clearer understanding of Z schemas and inspire the development of proof calculi for Z. 1 Introduction Implementations of proof support for Z [Spi 92, Nic 95] can roughly be divided into two categories. In direct implementations, the rules of the logic are directly represented by functions of the prover's implementation...

A new version of the Ergo theorem prover is under development. It uses a single tactic language, based on Angel, for tactic programming, user interface, and proof representation. This paper describes the language as it is used in each of these cases, and explains the details of its implementation in Qu-Prolog. An example from classical propositional calculus is included. 1 Introduction Ergo is an interactive proof tool that has been designed and implemented at the SVRC over the last ten years. It is implemented in Qu-Prolog (Robinson and Hagen, 1997), and is designed to be extensible, so that users can add new theories, tactics and user interfaces. Ergo 5 is currently under development. Having no inbuilt object logic, it is a generic prover that can be instantiated by providing a collection of axiomatic and/or definitional theories. The core of Ergo 5 provides support for (uninterpreted) sequents with named tuples of arbitrary terms as antecedents and single terms as consequents...

The paper presents the reection facilities of the speci cation language Slam-sl. Slam-sl is an object oriented speci cation language where class methods are speci ed by pre and postconditions. The reection capabilities permit managing these pre and postconditions in speci cations what means that semantic reection is possible. The range of interesting applications is very wide: formal speci cation of interfaces and abstract classes, speci cation of component based software, formalization of design pattern, using Slamsl as a pattern language, etc. The paper discusses the last two advantages in some detail.

We present a semantic representation of the core concepts of the specification language Z in higher-order logic. Although it is a "shallow embedding" like the one presented by Bowen and Gordon, our representation preserves the structure of a Z specification and avoids expanding Z schemas. The representation is implemented in the higher-order logic instance of the generic theorem prover Isabelle. Its powerful parsing and pretty-printing mechanisms can convert the concrete syntax of Z schemas into their semantic representation behind the scenes. Our representation essentially conforms with the latest draft of the Z standard and may give both a clearer understanding of Z schemas and inspire the development of proof calculi for Z. 1 Introduction Implementations of proof support for Z [Spi92b, Nic95] can roughly be divided into two categories. In direct implementations, the rules of the logic are directly represented by functions of the prover's implementation language. These implementat...