On the formal derivation of a proof of the invariance theorem

No abstract

Making Functionality More General

The definition for the notion of a "function" is not cast in stone, but depends upon what we adopt as types in our language. With partial equivalence relations (pers) as types in a relational language, we show that the functional relations are precisely those satisfying the simple equation f = f o fu o f, where "o" and "u" are respectively the composition and converse operators for relations. This article forms part of "A calculational theory of pers as types"

On a method for the formal design of multiprograms

We exemplify a method for the formal derivation of multiprograms, using the simple theory of Owicki and Gries as our main tool for coping with concurrency. In our first and simple example we derive a protocol for the problem of Concurrent Vector Writing, and in our second and more tricky example we design a distributed algorithm for the problem of Liberal Phase Synchronization

Programs and datatypes

We are programmers, in the sense that it is our concern to improve the process of program construction. Therefore we want to answer questions like: What is programming, why is it so difficult and error-prone, and how can we learn what is needed to make the process more manageable? In the following we shall address these issues in a relational framework. Section 10.1 gives an introductory overview explaining the background to our approach. Section 10.2 shows how we deal with (recursive and non-recursive) datatypes in the relational framework. Section 10.3 discusses programs in this context, concentrating on a class of programs characterized by relational equations of a specific but quite general shape. Program termination is the subject of Section 10.4. Finally, Section 10.5 briefly touches on the design and execution of (terminating) programs. For a more extensive treatment see [Doornbos 1996]

Safe combinations of services using B

The paper reports on the use of the B method and related tools to handle the feature interaction problem in telecommunications. The feature interaction problem states critical questions with respect to safety, sociological and legal aspects. Our approach proposes a new way to combine abstract machines and evaluates the resulting generation of proof obligations. The B method is a framework for specifying, refining and developing systems in a mathematical and rigorous, but simple way, and services are specied in the B method. The feature interaction problem is modelled simply as a violation of an invariant. The B method is supported by sofware that helps the specifier of services and features. We have not only modelled services within the B technology, but we have also extended possibilities of B by combining abstract machines