Agents in logic programming

The objective of this thesis is to explore ways of describing agents in logical theories. The contribution is that the logical theories we build are a generalised form of logic programs. Like normal logic programs, these theories have an intuitive declarative reading and a procedural interpretation to guide the implementation of automatic devices and software. Both human beings and machines can reason about these logical theories. We employ the amalgamation of object and meta-logic programs to model notions such as beliefs, goals and agent's \mental" activities. But we also accommodate less usual notions such as reactivity, openness, activation of goals and preference encoding, that have proved to be essential in realistic models of agents. Four logic programming languages to program agent with those features are introduced. We use an event-based approach to model dynamic universes with changing properties, concurrency and synergistic e ects. NOTE: This is a copy of the thesis with single spacing and smaller font than the original. Please, do not refer to the page numbering in here as this is di erent from that in the copies submitted to the University of London. i Acknowledgements Many people helped me to complete this thesis. Thanks and apologies to any whom I do not mention here. I specially want to thank my supervisor Bob Kowalski, for his systematic guidance and valuable support. Many thanks also to Fariba Sadri, Francesca Toni, Gerhard Wetzel, Murray Shanahan, Rob Miller, Keith Clark, Chriss Moss, Stephen Se, Torbjorn Semb D, Yongyuth Permpoontanalarp and the Temporal Reasoning, Arti cial Intelligence and Logic (TRAIL) seminar group for many useful discussions. Special thanks to Susan Peneycad for her careful proofreading of the thesis and for lending her intuition on the subtleties of the English language. I am also very grateful to Giorgio Tonella and Christoph Jung, for their opportune and useful comments. My wife Liliana, my mother Gloria, father, family and friends deserve special mention for providing so much love and enthusiasm. I gratefully acknowledge the support of the CONICIT-Universidad de Los Andes, Venezuela, for this thesis. ii