Semantic technologies and linked data, with a case study at the Consiglio Nazionale delle Ricerche (CNR) AldoGangemi Web evolution and resource dereferencing Webisevolvingfromawebofdocuments(oftencalledWeb1.0)toa webofentities(called,withsubtledifferencesinmeaning,semantic web,webofdata,Web3.0). Thisevolutionispassingalsothrough theavailabilitytouserstoedititscontentsandgeneratecomplex socialnetworksthroughsimpleinteractionparadigms(knownasso- cialweborWeb2.0). Thisishappeningprimarilythankstoadeeper exploitation of the Web architecture designed since the nineties,1 whichenablesthedereferencingandlinkingofwebresources(iden- tifiedbymeansofaWebaddress),throughsimplecommunication protocols(e.g. HTTP).Forexample,whenonewritestheaddress (URI)http://www.cnr.it(thewebaddressoftheportalofConsiglio Nazionale delle Ricerche, CNR) in a browser, the HTTP client of the browser dereferences that address by communicating with a serveratCNR,whichreturnsaHTMLpage,visualizedonitsturn 1http://www.w3.org/TR/webarch. JLIS.it.Vol.4,n.1(Gennaio/January2013). DOI:10.4403/jlis.it-5457 A.Gangemi,SemanticTechnologiesandLinkedData bythebrowser. Otherwebpagescanbepresentinthevisualized page, so creating a network of hypertextual links, which enables thebrowsingexperience. Thisisbasicallythewebofdocuments. Sometimesdereferencingisindirect,asinthecasewhenanaddress representsacalltoadatabase,e.g. whenlookingforone’staxdata intheAgenziadelleEntrate(theItalianfiscalauthority)website: thisisstillthewebofdocuments,butthedocumentsaregenerated outofaquerytoadatabase,whoseanswerisrenderedinHTML byusingXMLstylesheets. ThecaseofWeb2.0isamoresophisti- catedindirectdereferencing,whichalsoenablesdirectchangestoa databaseperformedbyusers: applicationssuchasvoiceprotocols, email,tagging,automaticloganalysis,opinionminingetc. converge inrich,customizableanddynamicHTMLpages,asinthecaseof Facebook. Two difficult problems: identity and semantic interoperability Web1.0and2.0havetwolimitations,whichactuallyexistininfor- mationsystemssincecenturiesago: identityandsemanticinterop- erability. The identity issue arises e.g. in the following example. AldoGangemihasdifferenthomepages(oneonhisinstitutesite, ISTC-CNR,onefromthewikiofhislab,STLab,oneontheseman- ticweb.org site etc. He is also registered on many other portals providingservicestothecitizen,tomembersofassociations,confer- encecommittees,commercialservicesetc. Moreover,hehasseveral accountsofsocialwebapplications(e.g. Facebook, Gmail, Flickr, iTunesetc.). Evenmore,AldoGangemiisadatumwithinpublicor personaldatabases,likeGoogleScholar,DBLPetc.;thatdatumhas identifiersthatareownedspecificallybythosedatabases,gathering JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.254 JLIS.it.Vol.4,n.1(Gennaio/January2013) thenasortof”positional”identitywithinoneoftheirtables).Finally, AldoGangemiiscitedinotherwebpages: articles,bibliographic references,eventreports. Nowtheissueis: howcanweknowthat (thephysicalorsocialperson)AldoGangemiistheentitydenoted byhishomepages,registrations,accounts,databaseIDs,citations? Intuitively, the issue is not limited to persons, but it impacts on everythingthathasanidentity: places,organizations,products,ser- vices,events,laws,ideas,concepts,fictionalthingsetc.Thesemantic interoperabilityissue,besidespurelysystem-orientedproblems(e.g. differentcomputationalplatforms),arisesfromtheidentityissue: ifwecannotresolvetheidentityofsomethingacrossthedifferent sourcesandsystemsthatrefertoit,itgetsreallydifficulttoaggre- gate(i.e. assemble)andintegrate(i.e. appropriatelyconnect)the informationaboutit. Thisisquitelimitingwhenconsideringthat therelationsbetweensomethingandsomethingelsecanbesimilar withindifferentsystems: therelationbetweenAldoGangemiand theemailmessagesaddressedtohim,orbetweenhimandhisrecip- ients,aresimilarinanyemailingsystem,butthosesystemsassign different identities to the same persons, if any. In addition, each systemworksonaproprietaryinfrastructure: differentlanguages, formats, protocols etc. All this makes data integration between differentsystemspartialinthebestcases. Some traditional solutions Inthelastyears,asortofcartelhasemergedbetweencommercial serviceproviderssuchasFacebook,Googleetc.,inordertomake socialnetworkdatainteroperable: thishoweverconcernsonlydata exchangethatarecommerciallyinterestingforthosesystems,and thirdpartyapplicationsthatcountonthem. Databasemanagement systemsusecomplexprocedurestointegratetheirdatawhenitis JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.255 A.Gangemi,SemanticTechnologiesandLinkedData required: schemaintegration,identityresolution,datawarehousing etc. Eachprocessistypicallymadeadhoconapairofdatabases. Partialsolutionsfordataintegrationalsocomefromdatamining ornaturallanguageprocessingtechniques. Forexample,thereare effectivestatisticalapproachesfornamedentityrecognitionandres- olution,aswellasfordiscoveringsimilarityandindirectrelationsin data. Documentannotationisanapproachthatcomesbackatleast to the beginning of 20th century: a document, or part of it (para- graphs,terms)areannotatedwithacategoryortagtakenfromsome knowledge organization system: thesauri, classification schemes, nomenclatures,controlledvocabularies,whichhavedevelopedin mostscientific,library,andcommercialdisciplines. Exemplarcases of similar large efforts include SnoMed, ICD, MeSH (medicine), Gettythesaurus(culturalheritage),Agrovoc(agriculture)etc. Re- cently,annotationproceduresareassistedeitherbycomputational support for manual annotation, or by automatic annotation algo- rithms(e.g. textclassification),withvariableprecision. The web of data In2006,TimBerners-Leeintroducedlinkeddata,asimpleandele- gantmethod2torealizesomepracticaldataidentityintegrationand interoperabilityontheWeb. Linkeddataareaimedatrealizinga webofdata(orEntities,orThings,dependingontheinteresttodata management,toentitylinking,ortosensorsandthingsinthephysi- calworld). Linkeddataisoneofthetechnologiesforthesemantic web(discussedinthenextsection),andconsistsoffourprinciples andmanygoodpractices. Theprinciplesinclude: 1. usewebaddresses(URI)asnamesforentities/things; 2http://www.w3.org/DesignIssues/LinkedData.html. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.256 JLIS.it.Vol.4,n.1(Gennaio/January2013) 2. useHTTPURIssothatpeoplecanlookupanddereference thosenames; 3. whensomeonelooksupaURI,provideusefulinformation, usingthestandards(RDF,RDFS,SPARQL,OWL,RIF); 4. include links to other URIs, in order to be able to discover morethingsanddata. Amonggoodpractices,it’susefultomentionthosethathavebest supportedtheLinkingOpenData(LOD)bootstrap,whosestateof playisvisualizedperiodicallyasacloud3: • useopenlicensestoobtainhighlyreusabledata; • usenon-proprietaryformats(e.g. CSVinsteadofExcel); • useW3Copenstandards(typicallyRDF,4SPARQL,5OWL6)to identifythings,sothatpeoplecanpointatyourstuff,newlinks canbecreated,betterqueriesandmoreextendedreasoning canbeperformed. ThesepracticesalsofitrecommendationsfromtheOpenDatamove- ment,andarecurrentlyadoptedinmanydifferentfields,including Public Administration data7 and are used in the integration and enrichmentofdata,forexamplefortheexpertfindingtask.8 TheLODCloudcontainslinkeddatafrommanydifferentdomains, inparticularbiomedicine,cultural,multimedia,bibliographic,geo- graphicetc. Anexampleofthepotentialoflinkeddataisshownin 3http://linkeddata.org. 4http://www.w3.org/RDF/. 5http://www.w3.org/TR/rdf-sparql-query/. 6http://www.w3.org/2004/OWL/. 7http://data.gov;http://data.gov.uk;http://dati.gov.it. 8http://data.cnr.it. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.257 A.Gangemi,SemanticTechnologiesandLinkedData figure1,agraphbuiltautomaticallybyanapplication(RelFinder9), whichincrementallyvisualizestherelationsbetweenanytwoenti- ties,providedthattheyhaveanidentityonthewebofdata. Inthe figure1,graphbuildingstartsfromtheentities: Figure1:TheemergingrelationsbetweentwoentitiesacrosstheLinking OpenDatagraph. Semantic web standards W3Copenstandards,primarilyRDF,10SPARQL11andOWL,12en- ableelegantandhomogeneousrepresentationof,aswellasquerying 9http://www.visualdataweb.org/relfinder.php. 10http://www.w3.org/RDF/. 11http://www.w3.org/TR/rdf-sparql-query/. 12http://www.w3.org/2004/OWL/. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.258 JLIS.it.Vol.4,n.1(Gennaio/January2013) andreasoningon,thedatafrommosttraditionaldatastructuresand datamodels. RDFisbasedonarecursivedatastructure,calledtriple,madeofa Subject,aPredicate,andanObject,analogouslytothemostabstract grammatical structure of Western languages, SVO (Subject-Verb- Object). Listing1:SampleRDFtriples. ’’Aldo Gangemi’’ RDFtriplescanbequeriedviatheSPARQLlanguage. Listing2:Queryontriplesin1 SELECT ?l WHERE { ?x . ?x ?l} JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.259 A.Gangemi,SemanticTechnologiesandLinkedData Thequeryinlisting2ontheprecedingpagegetstheanswer: l ’’Aldo Gangemi’’ EachtriplecontainsSubjectsandObjectsthathaveatype,whichis onitsturnaClass,e.g. EachtriplecontainsaPredicate(orProperty),whichtogetherwith classesformsthevocabulary(alsocalledschemaorontology)used by a dataset. In cases where logical validation and reasoning is required,avocabularyisdefinedintheOWL(OntologyWebLan- guage) standard,13 a language that allows the use of automated reasonerstoderivelogicalinferencesoutofdatastructures. Forex- ample,anautomatedreasonerinferstheinversesofexistingtriples, thesymmetrictriples,thetriplesholdingtransitively(whenappro- priateruleshavebeendefinedforthevocabulary)etc. With the expressive power of OWL and SPARQL on the web of data,onecanmakecomplexquestionstoheterogeneousknowledge sources,e.g. intheRomalLawdomain,thefollowingnaturallan- guagequestionscanbeformalizedasqueries,buttermsneedtobe mappedtoappropriateentitytypesinRDFandOWL.Inthiscase, underlinedtermsaresupposedtobemappedasclasses,bold-faced termsasproperties,andtermsinitalicsasspecificentitiesorvalues: -which Roman Law sources contain maxims concerning stipulation, cite Ulpian,andincludecommentariespublishedinthelast10years? 13http://www.w3.org/2004/OWL/. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.260 JLIS.it.Vol.4,n.1(Gennaio/January2013) -whichcasesappearedinCommonLawsystemscontaininterpretationsrel- ativetocontractsanalogoustostipulatio? Inordertoimprovevocabularyqualityandinferencecapabili- ties,additionalaxiomsneedtobedefined(e.g. whattypeofentities canbeanalogoustowhat,whatcanbecitedinwhatetc.). Therefore, vocabularydesignrequiresacertainaccuracyandqualitycontrol, which can be obtained by means of approaches oriented to user requirements,andwiththereuseofstandardvocabulariesandon- tologydesignpatterns,14knowntodescribethedomainofinterest, and/orsolvingthemodelingproblemsemergingfromuserrequire- ments. Semantic applications Availability of large open data can provide a good motivation to develop next generation applications, which build on both exist- ingandnovelsolutions,focusedonthesemanticparadigm: using meaningofdataasawidespreadorganizationalschema. Thelifecycleofasemanticapplicationistypicallythefollowing: 1. reengineering existing data, by producing datasets in RDF triples(data)andOWL(vocabularies); 2. linkingbetweenentitiesinmultipledatasets,andproduction ofnewtriples; 3. extractionofnewentitiesandtriplesbymeansofdatamining andnaturallanguageprocessingtechniques,andproduction ofnewtriples; 14http://www.ontologydesignpatterns.org. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.261 A.Gangemi,SemanticTechnologiesandLinkedData 4. reasoning on the logical structures obtained from previous steps,andpossibleproductionofnewtriples(materialization); 5. publishingofdatasetsonappropriateplatforms,forSPARQL querying; 6. presentationofenricheddatatobeusedbywebusers: textual, graphic,richsnippets,explorativeetc. Thelifecyclereflectsamultipleinterpretationofthetermsemantics. Insteps2and3,wereferprimarilytothelinguisticsemanticsthatis implicitintheanalyzedtexts;relatedtechnologiesarethoseoftext anddataanalysis,andaimsatrecognizingentities,names,terms, relations,facts,topicsetc. Onlyoncewehaveextractedthem,we canproducenewformaltriples. Insteps1,4,5,werefertological (or formal) semantics of data and schemas; related technology is basicallywhatwehavementionedinprevioussectionsas”semantic web”(whichisamixofwebscienceandknowledgerepresentation). Instep6.,werefertothesemanticsofuserinteraction. Technologiesorientedtolinguisticsemanticsallowe.g. torecognize entitiesintexts,andtoresolvetheiridentitywithrespecttoknown datasets. Onceidentityhasbeenresolved, itispossibletoenrich the dataset with known relations between that entity and other entities. Forexample,giventhefollowingtextfromtheproceedings ofEuropeanUnionParliament: The sensitivities of Northern Ireland are too important for anyill-informedbandwagoningontheInternationalFundfor Ireland. Raytheon has been welcomed to Derry by no less thanNobelPeacePrizewinners,JohnHume–oneofourown colleagues,andDavidTrimble. Raytheonwillbefundedby theIndustrialDevelopmentBoardinNorthernIreland. Not oneeuronoroneIrishpoundfromtheInternationalFundfor IrelandisgoingtoRaytheon. JLIS.it. Vol.4,n.1(Gennaio/January2013).Art.#5457 p.262

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