ThisvolumeconsistsoftherefereedpaperspresentedattheFifthInternational ConferenceonLogicProgrammingandNonmonotonicReasoning(LPNMR'99) heldatElPaso, Texas, inDecember1999. LPNMR'99isthe fthinaseriesofinternationalmeetingsonlogicprogramming andnonmonotonicreasoning. FourpreviousmeetingswereheldinWashington, U. S. A., in1991, inLisbon, Portugal, in1993, inLexington, U. S. A., in1995, and inDagstuhl, Germany, in1997. TheaimoftheLPNMRconferencesisto- cilitateinteractionsbetweenresearchersinterestedinlogicbasedprogramming languagesanddatabasesystemsandresearcherswhoworkintheareasofk- wledgerepresentationandnonmonotonicreasoning. Inadditiontopresentationsofacceptedpaperstheconferencewillfeaturetalks byfourinvitedspeakersMarcoCadoli, VladimirLifschitz, DavidMcAllester, andLeoraMorgenstern. ManypeoplecontributedtothesuccessoftheLPNMR'99conference. Special thanksareduetotheprogramcommitteeandtheadditionalreviewersforcareful evaluationofthesubmittedpapers. WewouldalsoliketothankGopalGuptaand DannyDeSchreyefortheire ortsincoordinatingtheschedulesofICLP99and LPNMR99, andGeorgGottlob, chairoftheLPNMRsteeringcommittee, who providedcontinuousadviseandsupporttotheprogramchairs. Theconference was nanciallysupportedbytheUniversityofTexasatElPasoandCompulog NetprovidedsupportforaEuropeaninvitedspeaker. December1999 MichaelGelfond NicolaLeone GeraldPfeifer ConferenceOrganization ProgramCo-Chairs MichaelGelfond(UniversityofTexasatElPaso, USA) NicolaLeone(ViennaUniversityofTechnology, Austria) ProgramCommittee JoseJulioAlferes(UniversidadedeEvora, Portugal) ChittaBaral(UniversityofTexasatElPaso, USA) NicoleBidoit(Universit edeBordeaux1, France) J]urgenDix(UniversityofKoblenz, Germany) ThomasEiter(ViennaUniversityofTechnology, Austria) FangzhenLin(TheHongKongUniversityofScienceandTechnology, China) JackMinker(UniversityofMaryland, USA) AnilNerode(CornellUniversity, USA) IlkkaNiemela(HelsinkiUniversityofTechnology, Finland) DinoPedreschi(UniversityofPisa, Italy) PasqualeRullo(UniversityofCalabria, Rende, Italy) ChiakiSakama(WakayamaUniversity, Japan) V. S. Subrahmanian(UniversityofMaryland, USA) FrancescaToni(ImperialCollege, London, U. K. ) MiroslawTruszczynski(UniversityofKentuckyatLexington, USA) HudsonTurner(UniversityofMinnesotaatDuluth, USA) MosheY. Vardi(RiceUniversity, USA) Jia-HuaiYou(UniversityofAlberta, Canada) PublicityChair GeraldPfeifer(ViennaUniversityofTechnology, Austria) AdditionalReviewers RobertoBarbuti StefanBrass KrysiaBroda FrancescoBuccafurri CarlosDamasio AlexanderDekhtyar PhanMinhDung UweEgly WolfgangFaber SergioGreco Je Horty KatsumiInoue ConferenceOrganization VII TomiJanhunen ChrisJohnson AntonisKakas HirofumiKatsuno VladimirLifschitz JorgeLobo ThomasLukasiewicz So anMaabout GiuseppeManco VictorMarek CristinelMateis YujiMatsumoto IaraMora MircoNanni LuigiPalopoli LuisMonizPereira GeraldPfeifer InnaPivkina SalvatoreRuggieri FaribaSadri FrancescoScarcello DietmarSeipel HirohisaSeki PatrikSimons TerrySwift HansTompits UlrichZukowski KewenWang TableofContents ContributedPapers FixedParameterComplexityinAIandNonmonotonicReasoning. . . . . . . . . . . 1 G. Gottlob, F. Scarcello, M. Sideri ClassifyingSemi-NormalDefaultLogicontheBasisofitsExpressivePower 19 T. Janhunen LocallyDeterminedLogicPrograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 D. Cenzer, J. B. Remmel, A. Vanderbilt AnnotatedRevisionPrograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 V. Marek, I. Pivkina, M. Truszczynski Belief, Knowledge, Revisions, andaSemanticsofNon-MonotonicReason
