The paper is a general overview of an approach to the semantics of logic programs whose aim is finding notions of models which really capture the operational semantics, and are therefore useful for defining program equivalences and for semantics-based program analysis. The approach leads

How do people know as much as they do with as little information as they get? The problem takes many forms; learning vocabulary from text is an especially dramatic and convenient case for research. A new general theory of acquired similarity and knowledge representation, latent semantic analysis

Abstract not found

Least fixpoints as meanings of recursive definitions.

on purely discrete state spaces only. In particular, various classes of hybrid automata induce finitary trace equivalence (or similarity, or bisimilarity) relations on an uncountable state space, thus permitting the application of various model-checking techniques that were originally developed for finite

then consider the bene ts of and describe, a more formal approach. We re-visit the scoping phase, and discuss the role of formal languages and techniques in the specification, implementation and evaluation of ontologies. Finally, we review the state of the art and practice in this emerging field,

and logic, and much progress has been made in developing verification algorithms, heuristics, and tools. This paper provides a survey of the theory of timed automata, and their role in specification and verification of real-time systems.

an ideal theoretical perspective and a more practical perspective; and (c) the building of large-scale applications based on BDI agents. In particular, an air-traffic management application will be described from both a theoretical and an implementation perspective.

) and to speed-accuracy paradigms; results are found to provide a basis for comparison of these paradigms. It is noted that neural network models can be interfaced to the retrieval theory with little difficulty and that semantic memory models may benefit from such a retrieval scheme.

Object-oriented languages were invented to provide an intuitive view of data and computation, by drawing an analogy between software and the physical world of objects. The detailed explanation of this intuition, however, turned out to be quite complex; there are still no standard definitions of such fundamental notions as objects, classes, and inheritance. Much progress was made by investigating the notion of subtyping within procedural languages and their theoretical models (lambda calculi). These studies clarified the role of subtyping in object-oriented languages, but still relied on complex encodings to model object-oriented features. Recently, in joint work with Martin Abadi, I have studied more direct models of object-oriented features: object calculi. Object calculi embody, in a minimal setting, the object-oriented model of computation, as opposed to the imperative, functional, and process models. Object calculi are based exclusively on objects and methods, not on functions or data structures. They help in classifying and explaining the features of object-oriented languages, and in designing new, more regular languages. They directly inspired my design of Obliq, an object-oriented language for network programming.