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The first part of the thesis provides an introduction to the logic programming language Prolog and some areas of current research. The use of compilation to make Prolog faster and more efficient is studied and a modified representation for complex structures is presented. Two programming tools are also presented. The second part of the thesis focuses on one problem which arises when implementing an Expert System using Prolog. A practical three-valued Prolog implementation is described. An interpreter accepts three-valued formulae and converts these into a Prolog representation. Formulae are in clausal form which allows disjunctive conclusions to rules. True and false formulae are stated explicitly and therefore the interpreter is able to perform useful consistency checks when information is added to the data base.

Thesis (M. Phil.)--University of Hong Kong, 1992.

Cognitive Science attempts to study entities which in some sense possess beliefs, intentions, desires etc. The preferred term in this thesis for such entities is agents. An attempt at a scientific analysis of agents however throws up a number of questions. What are the right concepts to describe agents? What kinds of formal notations permit perspicuous reasoning about agents? What can be said about the architecture and construction of agents? The introductory section of this thesis discusses these questions in some detail, using Dennett's ideas about intentional systems [Den87] as a point of departure. I then examine a number of studies from Artificial Intelligence, Logic, Natural Language semantics and Philosophy which give shape to the current state of the art in agent theory. This leads to the development of a mathematical model of multi-object/agent interaction, which I call the SRS-model (SRS - Synchronous Reactive Systems). I demonstrate the adequacy of the model by using it to formalise learning and games scenarios. Next, various logics are introduced which capture input-output and then belief-desire level descriptions of agents. These logics are given an SRS-model semantics, and adequacy is shown by modelling a psychological experiment (an agent in a Skinner Box). It is shown how the example can be formally analysed in terms of mechanisms and architecture at the SRS-level (including a computer simulation); at the level of behaviourism (using a temporal logic - APTL); and at an intentional level (using an epistemic-conative temporal logic ECTL). Some remarks are made about extending the analysis to multi-agent situations involving co-operation, competition and dialogue. Finally, a detailed survey is made of the main mathematical and logical resources available to the style of formal cognitive science advocated in this thesis. I include modal logic, including its epistemic and doxastic variants; the extension of modal logic to dynamic logic; and the various approaches recently developed in the logic of time.

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Kowalski's connection graph method provides a representation for logic programs which allows for the incorporation of better procedural control techniques than standard logic programming languages. A proposed search strategy for visual recognition which combines top-down and bottom-up techniques has been incorporated in a connection graph implementation. The connection graph representation also allows for the natural incorporation of constraint satisfaction techniques in logic programming. Kowalski's approach to incorporating constraint satisfaction techniques in connection graphs is examined in detail. It is shown that his approach is not efficient enough to be used as a general preprocessing algorithm but that a modified version may be of use. Increased control of search and the incorporation of consistency techniques increase the procedural adequacy of logic programs for representing knowledge without compromising the descriptive capacity of the form. / Science, Faculty of / Computer Science, Department of / Graduate

No description available.

No description available.