This book constitutes the refereed proceedings of the 9th European Conference on Logics in Artificial Intelligence, JELIA 2004, held in Lisbon, Portugal, in September 2004.
The 52 revised full papers and 15 revised systems presentation papers presented together with the abstracts of 3 invited talks were carefully reviewed and selected from a total of 169 submissions. The papers are organized in topical sections on multi-agent systems; logic programming and nonmonotonic reasoning; reasoning under uncertainty; logic programming; actions and causation; complexity; description logics; belief revision; modal, spatial, and temporal logics; theorem proving; and applications.
Logics have, for many years, laid claim to providing a formal basis for the study and development of applications and systems in artificial intelligence. With the depth and maturity of formalisms, methodologies and logic-based systems today, this claim is stronger than ever. The European Conference on Logics in Artificial Intelligence (or Journées Européennes sur la Logique en Intelligence Artificielle, JELIA) began back in 1988, as a workshop, in response to the need for a European forum for the discussion of emerging work in this field. Since then, JELIA has been organized biennially, with English as its official language, previous meetings taking place in Roscoff, France (1988), Amsterdam, Netherlands (1990), Berlin, Germany (1992), York, UK (1994), Évora, Portugal (1996), Dagstuhl, Germany (1998), Málaga, Spain (2000) and Cosenza, Italy (2002). The increasing interest in this forum, its international level with growing participation from researchers outside Europe, and the overall technical quality have turned JELIA into a major biennial forum for the discussion of logic-based approaches to artificial intelligence.