Jacob Brunekreef

Alma-O: an imperative language that supports declarative programming

We describe here an implemented small programming language, called Alma-O, that augments the expressive power of imperative programming by a limited number of features inspired by the logic programming paradigm. These additions encourage declarative programming and make it a more attractive vehicle for problems that involve search. We illustrate the use of Alma-O by presenting solutions to a number of classical problems, including α-β search, STRIPS planning, knapsack, and Eight Queens. These solutions are substantially simpler than their counterparts written in the imperative or in the logic programming style and can be used for different purposes without any modification. We also discuss here the implementation of Alma-O and an operational, executable, semantics of a large subset of the language.

Process Specification in a UNITY Format

In this paper a “UNITY Format” for process specifications is introduced. The format is based on conditions on process states and process data. Several aspects of this format are discussed: a straightforward normalisation of the parallel composition of processes, the relation between the ACP priority operator θ and conditions and, finally, the correspondence with a term rewriting system, which opens certain perspectives with respect to the validation and verification of a specification. Throughout the paper the simple and well-known PAR protocol serves as a running example.

Algebraic specification of dynamic leader election protocols in broadcast networks

The problem of leader election in distributed systems is considered. Components communicate by means of buffered broadcasting as opposed to usual point-to-point communication. In this paper three leader election protocols of increasing maturity are specified. We start with a simple leader election protocol, where an initial leader is present. In the second protocol this assumption is dropped. Eventually a fault-tolerant protocol is constructed, where components may crash and revive spontaneously.

A Transformation Tool for Pure Prolog Programs

This paper describes an interactive tool for transforming pure Prolog programs. The choice of (pure) Prolog semantics induces a number of conditions that have to be satisfied before a particular transformation step can be applied. The transformation tool has been developed using a programming environment based on algebraic specification. The paper describes the tool and reports on the design decisions, the implemented transformation steps, and the user interface.