Logics have, for many years, laid claim to providing a formal basis for the study and development of applications and systems in arti?cial intelligence. With the depth and maturity of formalisms, methodologies and logic-based systems - day, this claim is stronger than ever. The European Conference on Logics in Arti?cial Intelligence (or Journ' ees Europ' eennes sur la Logique en Intelligence Arti?cielle, 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 ?eld. Since then, JELIA has been organized biennially, with English as its o?cial language, previous meetings taking place in Rosco?, France (1988), Amsterdam, Nether- ' lands (1990), Berlin, Germany (1992), York, UK (1994), Evora, Portugal (1996), Dagstuhl,Germany(1998),M' alaga,Spain(2000)andCosenza,Italy(2002). The increasinginterestinthisforum,itsinternationallevelwithgrowingparticipation 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 arti?cial intelligence.
The 9th European Conference on Logics in AI, JELIA 2004, took place in Lisbon, Portugal, between the 27th and the 30th of September 2004, and was hosted by the Universidade Nova de Lisboa. Its technical program comprised 3 invited talks, by Francesca Rossi, Franz Baader, and Bernhard Nebel, and the presentationof52refereedtechnicalarticlesselectedbytheProgramCommittee among the 144 that were submitted, a number which in our opinion clearly indicates that the research area of logics in AI is one with a great and increasing interest.