Extending a Logic-Based Retrieval Model With Algebraic Knowledge

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ExtendingaLogic-BasedRetrievalModelWithAlgebraicKnowledge

Jean-PierreChevalletInstitutd’InformatiqueetdeMathematiqueAppliqueedeGrenoble(IMAG)FranceJean-Pierre.Chevallet@imag.fr

YvesChiaramellaInstitutd’InformatiqueetdeMathematiqueAppliqueedeGrenoble(IMAG)FranceYves.Chiaramella@imag.fr

AbstractAmajorneedofprecision-orientedretrievalsystemsistheavailabilityofhigh-levelindexinglanguageswhichcanallowtherepresentationandthemanipulationofelaboratedconceptsforbothindexingandqueryingprocesses.Suchelaboratedknowledgerepresentations,astheonedevelopedintheRIMEproject,needinturntobefullyintegratedwithintheunderlyingretrievalmodeltoensureproperandoptimaluseofthisknowledgeintheretrievalprocess.InthispaperwepresentfurtherdevelopmentsofthefuzzymodallogicretrievalmodelwhichwasfirstdevelopedandexperiencedintheRIMEproject.Thesedevelopmentsarepreciselyaimedtowardsabetterintegrationofthismodelandknowledgerepresentation.WeshowthatConceptualGraphsofSowahaveformalpropertieswhichallowagoodformalcontrolofthisintegration,andareinherentlywelladaptedtoIRrequirements.Thisstudyhastriggeredextensionsoftheinitiallogicmodelandadaptationsoftheconceptualgraphs’formalismwhicharealsopresentedhere.Finallythepaperpresentsthewayeverynotionofthetheoreticalretrievalmodelisexpressedintermsofaderivedoperationalmodelwhichhasbeenimplemented.

1IntroductionAmajorneedofprecision-orientedretrievalsystemsistheavailabilityofhigh-levelindexinglanguageswhichallowtherepresentationandthemanipulationofelaboratedconceptsforbothindexinglanguagesandqueryingprocesses.Heretheterm“precision-orientedsystems”hasamorespecificmeaningthancurrentlyunderstoodinIR:itreferstotheclassicalmeaningofhighprecisionperformancesandtotheabilitytodealwith“precise”-i.e.elaborated-concepts.ThesetwopropertiesaremandatoryfornumerousapplicationfieldsofIRwhereusersareskilledspecialistsworkinginspecificareas.GoodexamplesofsuchapplicationsfieldsareexperiencedwithintheRIME[2]andELEN[6]projectsdevelopedintheCLIPS-IMAGlaboratory:namelySoftwareReuseforELENandMedicineforRIME.Insuchenvironments,specialistsareeitherengineersorphysicians,corpusesaresoftwarecomponentdatabasesormedicalreportsandimages.Whatcharacterizestheseusersistheirinformationneedsandtheirrequirementsaboutinformationretrieval:beingdomainspecialiststheyusehighlevel,precise,intricatenotionsintheircurrentactivities,andtheyneedtocommunicatewitharetrievalsystemusingthislevelofdomainconcepts.Aconsequenceisofcoursethattheyrequirefromtheretrievalsystemtoprocesstheirqueriesatthislevelofconceptualexpression:theyoftencannotsupportforalongtimepoorprecisionperformancesduetoinadequateindexinglanguages.TheRIMEandELENprojectsconstitutetheframeworkwehavedesignedforinvestigatingprecision-orientedinformationretrievalsystems:RIMEismorespecificallydedicatedtomultimediainformationretrievalinmedicalinformation.TheprojectdealswithcorpusescombiningtextualinformationfrommedicalreportsandrelatedX-raypictures.ELENisamorerecentprojectdedicatedtocomplexobjectinformationretrievalwhoseapplicationdomainisSoftwareReuse.ExperimentationsofthisprototypeareontheirwayusingcorpusesofUNIXandLOOPSsoftwarelibraries.Thesetwoprojectsarebasedonthesameparadigmabouttheunderlyingmodels:thefuzzymodallogicmodel.ThismodelwasdesignedandimplementedforthefirsttimeintheRIMEproject[19].Inthenextsectionwediscuss

WorkshopsinComputingScience-MIRO19951somelimitationswefoundwhileimplementingthefirstversionofthemodelandwhicharemainlyrelatedtowhatwecalla“looseintegration”oftheknowledgerepresentationintheretrievalmodel.Thismeansthattheknowledgerepresentationsufferedalackofexplicitformalpropertiesallowingtoprovethatthematchingprocessofqueriesanddocumentsimplementedinthisearlierversionwascompletelydefined.Asweshallseeitinthenextsection,thismatchingprocessbetweencomplex(tree-like)semanticstructureswasbasedonasetofpreselectedcasesinsteadofbeingbasedonamoregeneral(i.e.formal)definitionofthismatch.Aresultofthatsituationisthatwecouldnotbesurethatallrelevantmatchingcasesbetweendocumentsemanticstructuresandquerysemanticstructureswereimplemented,andthusthatthematchingprocesswaspossiblymissingrelevantcases.Thisconsiderationtriggeredustofindamoresuitableknowledgerepresentationmodel.Insection3weexplainwhySowa’sConceptualGraphsfitperfectlywiththeserequirementsand,moregenerally,whytheyareinherentlymoresuitabletoanylogic-basedretrievalmodel.Asweshallsee,thisismainlyduetotheirformalproperties(acorrespondencewithfirstorderpredicates),andtotheexistenceofprimitiveoperatorswhichhelpinthecontroloftheirconstructionandtheiruseinthematchingprocess.InthissectionwealsopresentsomeadaptationswehaveintroducedtoimprovetheadaptationofConceptualGraphstoIRrequirements.Insection4weshowhowtheoriginalfuzzymodallogicmodelwasthenextendedtointegratetheseformalprop-ertiesofConceptualGraphs.Insection5wepresentthemainretrievaloperatorswhichhavebeenderivedfromthisimprovedtheoreticalmodel.AlltheseaspectshavebeenimplementedandexperimentedwithintheELENproject.Fi-nally,insection6wepresentsomeguidelinesforthevaluationofthepartialimplication.Wehavechosentoemphasizeherethemodelingaspectsoftheproject(boththeoreticalandoperational);thoughalreadyadvancedimplementationaspectswillbedetailedinfurtherpublications.ItshouldbecleartothereaderthatbothRIMEandELENresearchprojectsarededicatedtoexplorelogicbasedapproachtomultimediaIR.Ourmainconcernatthisstepistoidentifyandexperimentusefulfeatures1ofsuchmodels,