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An applicative language called HOPE is described and discussed. The underlying goal of the design and implementation effort was to produce a very simple programming language which encourages the construction of clear and manipulable programs. HOPE does not include an assignment statement; this is felt to be an important simplification. The user may freely(More)
Casl is an expressive language for the formal specification of functional requirements and modular design of software. It has been designed by CoFI, the international Common Framework Initiative for algebraic specification and development. It is based on a critical selection of features that have already been explored in various contexts, including(More)
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The properties of a simple and natural notion of observational equivalence of algebras and the corresponding specification-building operation are studied. We begin with a defmition of observational equivalence which is adequate to handle reachable algebras only, and show how to extend it to cope with unreachable algebras and also how it may be generalised(More)
We present the Mobile Resource Guarantees framework: a system for ensuring that downloaded programs are free from run-time violations of resource bounds. Certificates are attached to code in the form of efficiently checkable proofs of resource bounds; in contrast to cryptographic certificates of code origin, these are independent of trust networks. A novel(More)
The purpose of a logical framework such as LF is to provide a language for deening logical systems suitable for use in a logic-independent proof development environment. All inferential activity in an object logic (in particular, proof search) is to be conducted in the logical framework via the representation of that logic in the framework. An important(More)
The behavioural semantics of specifications with higher-order logical formulae as axioms is analyzed. A characterization of behavioural abstraction via behavioural satisfaction of formulae in which the equality symbol is interpreted as indistin-guishability, which is due to Reichel and was recently generalized to the case of first-order logic by Bidoit et(More)
The program development process is viewed as a sequence of implementation steps leading from a spe-ciication to a program. Based on an elementary notion of reenement, two notions of implementation are studied: constructor implementations which involve a construction \on top of" the implementing speciication, and abstractor implementations which additionally(More)
Parameterisation is an important mechanism for structuring programs and specifications into modular units. The interplay between parameterisation (of programs and of specifications) and specification (of parameterised and of non-parameterised programs) is analysed, exposing important semantic and methodological differences between specifications of(More)