Abstract
This paper presents and discusses the design and the development of a pattern recognition agent based on neural networks. This agent is part of an intelligent navigation system, providing it with the necessary vision abilities so that it can be placed on a strange environment in order to explore and recognise its structures and specificities. Although similar, the properties of the recognised objects change through time and according to each specific environment. The flexibility required by such recognition process was implemented by several pattern recognition agents. Each agent is based on a neural network and can be trained on-line by a parallel training algorithm to allow an effective real time utilisation.

Abstract
This article presents an evaluation study of point-to-point and collective communication performance on a parallel processing system, a 16 node Parsytec PowerXplorer, using three different communication environments: PARIX, PVM and MPI.

Abstract
This paper has two purposes: first, to describe an experiment made in an undergraduate course, using Internet services to improve the speed and ease of communication between students and teaching team. We claim that the very positive results we obtained may very easily be reproduced in any course, with undergraduate students from the first year on. The second purpose is to discuss some possible directions the authors are planning to follow, in what concerns the utilization of Internet in education. Virtual environments such as MUDs and the automatic marking-up of problems submitted through WWW forms are steps towards what might end up as a full-blown Distance Education Environment.

Abstract
We propose a new semantics for rewrite systems based on interpreting rewrite rules as inequations between terms in an ordered algebra. In particular, we show that the algebra of normal forms in a terminating system is a uniquely minimal covering of the term algebra. In the non-terminating case, the existence of this minimal covering is established in the completion of an ordered algebra formed by rewriting sequences. We thus generalize the properties of normal forms for non-terminating systems to this minimal covering. These include the existence of normal forms for arbitrary rewrite systems, and their uniqueness far confluent systems, in which case the algebra of normal forms is isomorphic to the canonical quotient algebra associated with the rules when seen as equations. This extends the benefits of algebraic semantics to systems with non-deterministic and non-terminating computations. We first study properties of abstract orders, and then instantiate these to term rewriting systems.

Abstract

Abstract
This text presents an implementation of a concurrent attribute evaluator system. This system was developed with the main objective of allowing the implementation of several strategies of concurrent attribute evaluation and not to build a faster compiler to a specific case. The system is implemented in a tightly-coupled machine. One realistic compiler was built and the first results are discussed.