Ontology-based semantic infrastructure for service interoperability

serviceinteroperability󰀁

D.Bianchini,V.DeAntonellis,M.Melchiori

Universit`adiBrescia

Dip.Elettronicaperl’Automazione

ViaBranze,3825123Brescia-Italy

bianchin|deantone|melchior@ing.unibs.it

Abstract.Inthispaper,weprovideageneraloverviewofourrecentresearchcontributions,withfocusontheproposedapproachforbuildingserviceontologiestoserveasaninteroperabilitysemanticinfrastructureinwebinformationsystems.

1Introduction

Interoperabilityissuesrelatedtotheincreasingneedofcooperationandcom-municationamongusers/applicationsovertheWebareintensivelyaddressedintheliterature.Inparticular,Web-basedinformationsystemsrequireadvancedmethodsandtoolstoeffectivelysupportusersinthelocalizationandretrievalofinformationandservicesontheWeb.Techniquesandapproachesfortheor-ganizationandrepresentationofsemanticcontentsofinformationandservicesassumearelevantrole.Theproblemoforganizingsemanticknowledge,accordingtoclassificationschemesbasedonconceptsandsemanticlinksamongconceptsatdifferentabstractionlevels,isarelevanttopicaddressedbytheresearchworkontheSemanticWebandonontologiesfortheSemanticWeb[3].OntologiesareconsideredastheenablingtechnologyfortheSemanticWebandmethodsandtoolsforontologydefinitionarebeingstudiedforinteroperabilitypurposes([11,13].

Techniquesandapproachesforthedesignofconceptontologiesthroughclas-sificationtechniquesandforthedefinitionofthematicviewsinordertosupporttheusersinthelocalizationandretrievalofinformationandservicesontheWebarebeingdeveloped[14].Classificationtechniquesbasedonmatchingandclus-teringalgorithmshavebeenstudiedtofindandclassifycorrespondencesamongelementsofheterogeneousschemas[10].

TheresearchteamatUniversityofBresciahasproducedcontributionstothedevelopmentofclassificationtechniquesforanalysis,matchingandclusteringofstructured[6]andsemistructureddataintheframeworkoftheintegrationtoolenvironmentartemis[7].Anontologydesignmethodologyforknowledgesharingandservicecompositionhasbeenproposedin[4].

Forserviceontologies,DAML-S[1]hasbeenproposedintheareaofSemanticWebtodescribeservicesemanticsandseveralformalmodelsandlanguageshavebeenproposedforhandlingservicesfromasemanticpointofview.Semantic

󰀁

ThisworkhasbeenpartiallysupportedbytheEuropeanEUNoEINTEROP.

descriptionsarespecificallyneededformatchmakingbetweenservicedemandsandoffersandforservicedynamicdiscovery.Techniquesformatchmakinghavebeenstudiedtakingintoaccountqualityofservices[8,12].Recently,ontology-baseddiscoveryapproachesarebeingdeveloped[9].

TheresearchteamatUniversityofBresciahasproducedcontributionstothedevelopmentoftechniquesforservicemodelingandanalysisinordertoidentifycompatibleservices,i.e.servicesthatcansubstituteeachotherintheexecutionofcooperativeprocesses[4,5].

Inthispaper,weprovideanoverviewofourapproachforbuildingserviceontologiestoserveasaninteroperabilitysemanticinfrastructureinWebin-formationsystems.Thepaperisorganizedasfollows.Section2describesthemethodologicalapproachtoserviceontologydesign.Section3discussesfuturework.

2Serviceontologydesign

Onpurposeofservicemodelingandclassification,aservicemodelhasbeenpro-posedinthecontextofMAISproject[2].Themodeltakesintoaccount:theserviceproviderperspective,specifyingwhoprovidestheservice,onwhatchan-nelisprovided,whattheservicedoesandhowtoinvokeitsfunctionalities;andtheservicerequesterperspective,associatedtoaparticularuserprofileandop-eratinginaparticularcontext,thatspecifieswhorequirestheservice,theuser’scontextandwhichlevelofqualityisrequired.Themodelconsidersbothfunc-tionalandnon-functionalaspects.

Servicefunctionaldescription.Aserviceismainlydescribedbyasetofop-erationsandI/Oentitiesprovidingtheserviceinterfacedescription.Pre-andpost-conditionsarestatedoneachsingleoperationandonthewholeservice.TheyarelogicalexpressionsonI/Oentitiesthatmustbeverifiedbeforetheexecutionofanoperationorofthewholeserviceandthataresatisfiedaftertheexecution,respectively.Furthercharacterizationofservicesregardstheorderinwhichtheoperationsaretobeperformed,atwhatinputmessagestheservicereactsandwhatoutputmessagesitproducesduringstatetransitions.Theseaspectsarerepresentedinthemodelbymeansoffinitestateautomata,whereeachstatetransitionislabeledwiththeinputmessagethatcausesthetransitionandtheoutputonethatisproducedbythetransition.

Servicenon-functionaldescription.Withrespecttothenon-functionalas-pects,weconsiderthateachserviceischaracterizedbyasetofqualitypa-rameters.Someofthemaregeneralpurposeparametersprovidedbyavailablestandardclassifications(forexample,ISO8402,partoftheISO9000standard),butweconsideralsomorespecificapplicationdependentqualityparameters(forexample,thenumberofcreditcardsacceptedbyanon-lineticketreservationservice).Eachqualityparameterisdescribedbymeansofaname,oneormoremeasureunitsandaparametertype.

Inourapproach,functionalaspectsareusedtoorganizeservicesintotheserviceontologyandtopermitservicediscoveryonthebasisofuserfunctionalneeds.Non-functionalaspectsareexploitedtofurtherimprovetheservicedis-coveryaccordingtotheuserqualityrequirements.Inparticular,intheservice

ontologywerepresentservicesatdifferentlevelsofabstractionandtothispur-poseweintroducethreekindsofelements.

Concreteservice.Aconcreteservicerepresentsadirectlyinvocableservice,thatis,thedescriptionoftheserviceimplementationasproposedbytheserviceprovider.Itisdescribedintermsofinterface,behavior,qualityandimplementa-tionfeatures.Inourontologydesignapproachweanalyzeinterfaceandbehav-ioraldescriptionofconcreteservicestoestablishsemanticrelationshipsbetweenthemandtogroupthemintosets(clusters)ofsocalledcompatibleservices.Abstractservice.Anabstractservicerepresentsaclusterofcompatiblecon-creteservicesandisdescribedbymeansofinterfaceandqualityparametersanditisnotrelatedtoaparticularimplementation.Twokindsofrelationshipsbe-tweenabstractservicesareestablished,theis-arelationship,thatholdswhenanabstractserviceoffersatleastthesamefunctionalitiesofanotherone,andis-part-ofrelationship,thatisobtainedwhenanabstractservicecanbeviewedasthecompositionofotherones.

Servicecategories.Servicecategoriesarechosenfromavailablestandardclas-sifications(forexample,theUniversalStandardProductsandServicesClassifi-cationUNSPSC)toprovidetopic-basedviewonthesetofunderlyingabstractandconcreteservices;eachcategoryisassociatedtooneormoreabstractser-vices.

Accordingtothepresentedservicemodelandtotheconsideredlevelsofabstraction,wedevelopedamethodologytobuildaserviceontology,articulatedinthreephases.

1.Analysis.Inthisphaseconcreteservicesarecomparedonthebasisoftheirinterfaceandtheirbehaviortoevaluatetheirsimilarityaccordingtoproperlydefinedsimilaritycriteria.Weightedsemanticrelationshipsareestablishedamongthemonthebasisoftheperformedsimilaritycomputation.Twoconcreteservicesaregroupedinthesameclusterwhentheweightofsemanticrelationshipsconnectingthemisgreaterthanagiventhreshold(similaritylayer).

2.Abstraction.Inthisphaseforeachclusterofsimilarconcreteservicesanabstractserviceisbuilt,followinganintegrationprocess.Inparticular,op-erationsandI/Oentitieswhichdescribetheinterfacesofconcreteservicesbelongingtothesameclusterareunifiedtoobtaintheabstractservicein-terface.Mappingrulesaredefinedtorelatetheinterfacedescriptionoftheabstractservicewiththecorrespondinginterfacedescriptionsoftheconcreteservicesinthecorrespondingcluster(abstractlayer).

3.Categorization.Finally,inthisphaseabstractservicesareassociatedtoser-vicecategories;categoriesareorganizedinastandardgeneralizationtaxon-omyandadomainexpertdefinesassociationlinksbetweeneachleafcategoryinthetaxonomyandoneormoreabstractservicesintheunderlyinglayer(categorylayer).Aftertheapplicationofthesethreephases,theobtainedontologyisformallydescribedaccordingtoXML-basedlanguagesandcanbeexploitedtoenhancetheservicediscoveryonthebasisofuserfunctionalandnon-functionalrequire-ments[5].

3Futurework

Futureresearchactivitywillfocusonthedevelopmentofatoolenvironmentforservicediscoverybasedonserviceontologiesforthesemanticservicedescriptionandtherepresentationofsemanticrelationshipsamongservices.Serviceon-tologiescanbeusedforsharingknowledgeonservicesandforservicediscovery.Relevanteffortwillbedevotedtothedevelopmentforontology-basedalgorithmsandtechniquesformatchmakingbetweenservicedemandsandserviceoffers,andfordynamicservicediscovery.

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