Get on the Linked Data Web!

Get on the Linked Data Web!Tudor Groza, The University of QueenslandArmin Haller, CSIRO ICT CanberraMeta 2011Canberra, 26 May 2011

Linked DataWhy now ?Haller, Groza - Get on the Linked Data Web! (Meta 2011)2

2007 Gartner predictionsDuring the next 10 years, Web-based technologies will improve the ability to embed semantic structures [… it] will occur in multiple evolutionary steps …By 2017, we expect the vision of the Semantic Web […] to coalesce […] and the majority of the Web pages are decorated with some form of semantic hypertext…By 2012, 80% of the public Web sites will use some level of semantic hypertext to create SW documents […] 15% of public Web sites will use more extensive Semantic Web-based ontologies to create semantic databases …Haller, Groza - Get on the Linked Data Web! (Meta 2011)3RDFa, microformats (hcard, hatom ,etc …)[Adapted from Ivan Herman (W3C), RDFa, 2011]

Metadata in UseHaller, Groza - Get on the Linked Data Web! (Meta 2011)4[Peter Mika (Yahoo!), RDFa, 2011]

Australian contextDraft principles for the Open Public Section InformationHaller, Groza - Get on the Linked Data Web! (Meta 2011)5

Technical context6Haller, Groza - Get on the Linked Data Web! (Meta 2011)pngsvgKRAJAXSpeechRecognitionHTMLlinkbackSemantic WebTechnologiesWCAGCoreferenceCSSWebAppsRDFSPARQLEntityExtractionURIsSSLLinkedDataDLOWLHTTPJavaScriptSKOSTheoremProvingXPathRIFXMLGRDDLWebTechnologiesLogicProgrammingSemanticTechnologiesXSLT[Sandro Hawke(W3C), Introduction to Linked Data, 2010]

Why Linking Data?Applications can find data… without centralizationNo central bottlenecksNo central point-of-failureNo central policiesNo need for permissionUse existing …social structuresWeb structures 7Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Data flow8Web Data AppsInference(Knowledge discovery)Linked DataSemantic dataData in SQL DBsEtc …Data inSpreadsheetsCrowd sourcedataXMLDataRaw SensorDataHaller, Groza - Get on the Linked Data Web! (Meta 2011)[Adapted from Sandro Hawke(W3C), Introduction to Linked Data, 2010]

Linked Data cloud growthHaller, Groza - Get on the Linked Data Web! (Meta 2011)9As of May 2007

Linked Data cloud growthHaller, Groza - Get on the Linked Data Web! (Meta 2011)10As of February 2008

Linked Data cloud growthHaller, Groza - Get on the Linked Data Web! (Meta 2011)11As of July 2009

Linked Data cloud growthHaller, Groza - Get on the Linked Data Web! (Meta 2011)12As of September 2010[Richard Cyganiak, AnjaJentzsch, Linking Open Data cloud diagram, 2011]

Linked Data principles1. Enable linkingGood Website design2. Publish semantic (meta)dataExport data in RDF3. Use real (live) URIsThe heart of Linked Data1414

1. Enable linkingPut your information on your websiteInvest in content managementConsider offering public APIsUse goodURLsReadable, unambiguous … even in 10 yearshttp://example.com/index.php?123456 http://example.com/about/staff/john-doeURL survival planSupport …CachingContent negotiation1515[Adapted from Sandro Hawke(W3C), Introduction to Linked Data, 2010]

2. Publish semantic dataSemantic data RDFProvide comprehensive information for all itemsFor each question about the item … provide an answer16Premier?Nickname?Capital?16

2. Publish semantic dataRDFRDF – Resource Description FrameworkKnowledge representation language for the Semantic WebAdd structured information to Web resourcesRDF as data modelStatements about Web resources Triples: Subject – Predicate – ObjectGraph on URIs1717

2. Publish semantic dataURIsURI – Uniform Resource IdentifierCompact sequence of characters …… identifies an abstract or physical resource[RFC3986]URI ≈ URLhttp://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001Linked Data worldURI references18Haller, Groza - Get on the Linked Data Web! (Meta 2011)

2. Publish semantic dataRDF (cont.)RDF triplesSubject: URI reference or BNodePredicate: URI referenceObject: URI reference or BNode or LiteralRDF “data types”URI referencesBNodes– blank nodes  node without a nameLiterals – actual values of simple (usual) data types, e.g., int, long, string, etc…1919

2. Publish semantic dataRDF Example20http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001PublisherTitleAuthorBook seriesEditor20

2. Publish semantic dataRDF Example (cont.)21http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001has adc:titlewhich is21

2. Publish semantic dataRDF Example (cont.)22http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001has adc:creatorwhose name ishasanotherwhose name isdc:creator22

2. Publish semantic dataRDF Example (cont.)23http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001has awhich isdc:publisher23

2. Publish semantic dataRDF Example (cont.)24http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001is part ofbibo:bkserieswhich is24

2. Publish semantic dataRDF Example (cont.)25http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001is part ofwhich isdc:publisherbibo:bkserieswhich ishas a25

2. Publish semantic dataRDF Example (cont.)@prefix dc: <http://purl.org/dc/terms/> .@prefix bibo: <http://purl.org/bibo/> .@prefix : <http://www.morganclaypool.com/book/> .:S00334ED1V01Y201102WBE001 dc:title “Linked Data …” .:S00334ED1V01Y201102WBE001 dc:creator “Tom Heath” .:S00334ED1V01Y201102WBE001 dc:creator “Christian Bizer” .:S00334ED1V01Y201102WBE001 dc:publisher “Morgan & Claypool” .:S00334ED1V01Y201102WBE001 bibo:bkseries “Synthesis Lectures …” .26Haller, Groza - Get on the Linked Data Web! (Meta 2011)

2. Publish semantic dataOntologiesRDF triples use predicates to link

How about assigning meaning / semantics to resources?2727

2. Publish semantic dataOntologies (cont.)OntologiesShared conceptualization of a domainClassification of domain conceptsMeaningful relations between domain conceptsIn essence … “typed”schema28

2. Publish semantic dataOntologies (cont.)29http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001has adc:creatorwhose name isishasanotherPersoniswhose name isdc:creator29

2. Publish semantic dataOntologies (cont.)Ontology defines (e.g. FOAF ontology)Person Class URI – e.g., http://xmlns.com/foaf/Agent A perspective of the concept via attributes / properties: name, age, gender, …ExampleTom Heathis-aPersonChristian Bizeris-aPersonTom Heath, Christian Bizer – characterized by the attributes defined in the Person class3030

A bit of history …A first use case for RDF was website metadata3. Use real (live) URIs31ExampleWebsite of city of CanberraSubjecthttp://www.canberra.com.auPropertyWhen was it created?Value10-11-200831

3. Use real (live) URIs (cont.)This looks greatWeb page has a URLContent and the metadata is served via BrowserUnfortunately … it didn’t really workBecause …3232

3. Use real (live) URIsThe problemThe problemSo what is the URI of Canberra?Canberra is a city not a Web pageCanberra was established on 12-03-1913www.canberra.com.au was created on 10-11-2008RequirementsDon’t mix Canberra with www.canberra.com.auGet data via existing protocols… a challenge3333[Adapted from Sandro Hawke(W3C), Introduction to Linked Data, 2010]

3. Use real (live) URIs (cont.)Identifiers are required for thingsPeople, places, companies, products, courses, schools, buildings, plants, concerts, talks, species of plants, songs, musicians, etc …… all the things we have questions about… and all the questions… and all the answersWhich become things on their own3434[Adapted from Sandro Hawke(W3C), Introduction to Linked Data, 2010]

3. Use real (live) URIsSolutionsSolution 1 - Hash URIIn HTMLhttp://www.w3.org/People/Berners-Lee/#SpeakingSection in a webpageHowever, fragment semantics are up to content-type …In RDFhttp://www.w3.org/People/Berners-Lee/card#iFragment can be ANYTHING in the worldIdentifies Tim Berners-Lee not a section in the HTML page3535

3. Use real (live) URIsSolutions (cont.)Solution 2 - Slash URIsIn BrowserGET http://dbpedia.org/resource/CanberraServer responds with redirect303 See otherLOCATION http://dbpedia.org/page/CanberraTwo URIsA URI for the thing itself (in RDF for machines)A URI for a Web page (in HTML for humans)36

One last thing … integrationFollowing the principles… create semantic data… publish semantic data… how about integration / linking?SolutionsRe-using established URIsExplicit entity consolidation (via URIs)SPARQL queries37Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Explicit entity consolidation (via URIs)38Haller, Groza - Get on the Linked Data Web! (Meta 2011)http://www.morganclaypool.com/book/S00334ED1V01Y201102WBE001has adc:creatorwhose name ishttp://tomheath.com/id/mehasanother?http://data.semanticweb.org/person/tom-heathwhose name isdc:creator

Explicit entity consolidation (via URIs)Linking similar concepts publishing in different datasetsIn principle, two types of relationsowl:sameAs – strong assertion!rdfs:seeAlso – weak (loose) relation39Haller, Groza - Get on the Linked Data Web! (Meta 2011)

SPARQL queriesOn-the-fly integrationSPARQLQuery language for semantic data (RDF)Across diverse datasets… similar to SQL from the DB world40Haller, Groza - Get on the Linked Data Web! (Meta 2011)

SPARQL queries41Haller, Groza - Get on the Linked Data Web! (Meta 2011)prefix go: <http://purl.org/obo/owl/GO#>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>prefix owl: <http://www.w3.org/2002/07/owl#>...select ?genename ?processnamewhere{ graph <http://purl.org/commons/hcls/pubmesh> { ?paper ?p mesh:D017966 . ?article sc:identified_by_pmid ?paper. ?gene sc:describes_gene_or_gene_product_mentioned_by ?article. } graph <http://purl.org/commons/hcls/goa> { ?protein rdfs:subClassOf ?res. ?res owl:onPropertyro:has_function. ?res owl:someValuesFrom ?res2. ?res2 owl:onPropertyro:realized_as. ?res2 owl:someValuesFrom ?process. graph <http://purl.org/commons/hcls/20070416/classrelations> {{ ?process <http://purl.org/obo/owl/obo#part_of> go:GO_0007166} union { ?process rdfs:subClassOfgo:GO_0007166 }} ?protein rdfs:subClassOf ?parent. ?parent owl:equivalentClass ?res3. ?res3 owl:hasValue ?gene. } graph <http://purl.org/commons/hcls/gene> { ?gene rdfs:label ?genename } graph <http://purl.org/commons/hcls/20070416> { ?process rdfs:label ?processname}}MeSH: Pyramidal NeuronsPubMed: Journal ArticlesEntrez Gene: GenesGO: Signal Transduction[Ivan Herman(W3C), Semantic Web Adoption and Applications, 2011

Linked Data principles - Recap1. Publish semantic data2. Enable linking3. Use real (live) URIs42Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Open Public Sector Information - Draft principles - Open access to informationFreeBased on open standardsEasily discoverableUnderstandableMachine-readableFreely reusable and transformableRobust information asset management frameworksadequately describing information assets using appropriate metadatadocumenting known limitations on data quality and caveats on data usepreserving the agency's information assets for appropriate periods of time43Haller, Groza - Get on the Linked Data Web! (Meta 2011)RDF – Semantic DataLive URIS + Linking enabledQualityAvailabilityPreservation

Open Public Sector Information - Draft principles - Findable informationEnsuring that published information has high quality metadata …Publishing the agency's information asset register to enable […] to identify the available information resources from a single sourceOpen and accessible formats onlineOpenMachine-readableSearchable and indexable by commonly used Web search applications44Haller, Groza - Get on the Linked Data Web! (Meta 2011)Live URIS + Linking enabledLinkedDataWeb !

In practice …45Haller, Groza - Get on the Linked Data Web! (Meta 2011)

RDF … a “tool” for agentsRDF annotations often express metadata …usually stored in a separate .rdf file useful for agents, limited use for humans46Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Data for the Web of DataApart for relational DBs, most of the Web content is in … (X)HTMLNew content is generated on a daily basisQuestHow do get structured data from this content?47Haller, Groza - Get on the Linked Data Web! (Meta 2011)[Adapted from Ivan Herman (W3C), RDFa, 2011]

The “traditional” WebAuthors create HTML content… do not generate individual and separate RDF/XML filesReasons?RDF/XML is complexIt requires separate storage, generationIn any situation … it represents an overhead48Haller, Groza - Get on the Linked Data Web! (Meta 2011)[Adapted from Ivan Herman (W3C), RDFa, 2011]

Solution … RDFaAdd extra structured content to(X)HTML pagesAllow processors to extract this information and turn it into RDFRDFa … a “tool” for agents and humans49Haller, Groza - Get on the Linked Data Web! (Meta 2011)[Adapted from Ivan Herman (W3C), RDFa, 2011]

RDFaRDFa = RDF in attributesMarkup data in Web pagesEncodes RDF triples in (X)HTMLRepresents a complete serialization of RDFMechanismAdds extra attributes in (X)HTMLUses namespaces and URIsIntegration is just as easy as in RDF51Haller, Groza - Get on the Linked Data Web! (Meta 2011)

RDFa example – HTML<html> <head>… </head> <body>Morgan & Claypool Publishers Linked Data Evolving the Web into a Global Data Space Tom Heath Christian Bizer Synthesis lectures on The Semantic Web: Theory and Technology James Hendler, Series Editor </body></html>52Haller, Groza - Get on the Linked Data Web! (Meta 2011)

RDFa example – RDFa<html prefix=“dc: http://purl.org/dc/terms/”base="http://www.morganclaypool.com/book/S00334…WBE001"> <head>… </head> <body>Morgan & Claypool Publishers Linked Data Evolving the Web into a Global Data Space Tom Heath Christian Bizer Synthesis lectures on The Semantic Web: Theory and Technology James Hendler, Series Editor </body></html>53Haller, Groza - Get on the Linked Data Web! (Meta 2011)

In essence …The same (X)HTML file containing RDFaIs used … unchanged … by browsersBrowsers ignore attributed they don’t reconigzeCan be used by specialized processors to extract RDF54Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Datasets, tools and applications5555

Raw datasetsGreat … but not really there yetAPIs enable access… but not necessarily enable linking …… it is still a step ahead though …56Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Raw datasets (cont.)Australian Government57Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Raw datasets (cont.)US Government58Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Linked Data datasetsDBPediaCommunity effortExtract structured information from Wikipedia info boxesCore of the Linked Data Web59Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Linked Data datasets60Haller, Groza - Get on the Linked Data Web! (Meta 2011)@prefix dbpedia <http://dbpedia.org/resource/>.@prefix dbprop <http://dbpedia.org/property/>.dbpedia:Canberradbprop:name "Canberra" ;geo:lat "-35.308056" ;geo:lat "35.307499" ;geo:long "149.124420" ;geo:long "149.124451" ;dbprop:est "1913-03-12" ;dbprop:populationTotal "315868" ;dbprop:area "814" ; ...dbpedia:AIS_Arenadbpedia:locationdbpedia:Canberra ;

Linked Data datasets61Haller, Groza - Get on the Linked Data Web! (Meta 2011)BBCNatureProgramsMusic

Linked Data datasets (cont.)New York TimesAs of January 2010 … 10,000 subject headings~3,000 organizations~5,000 people~2,000 locations62Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Linked Data datasets (cont.)UK Government – data.gov.uk6,900 datasetsDept. for Business, Innovation and SkillsDept. for TransportDept. of Health63Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Linked Data datasets (cont.)64Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Storage SupportVirtuosoRDF triple storeSPARQL accesshttp://virtuoso.openlinksw.com/TalisSaaSCloud-based RDF storageSPARQL accessREST APIshttp://www.talis.com/platformSesameRDF triple storeSPARQL accesshttp://www.openrdf.org/65Haller, Groza - Get on the Linked Data Web! (Meta 2011)

Indexing, APIs & FrameworksSindice.com & Sig.maThe Semantic Web indexLarge scale data acquisitionData discovery & Mash-upSynchronization RDF APIsJenaARC2Any23FrameworksSILKPAGET66Haller, Groza - Get on the Linked Data Web! (Meta 2011)

RDFa adopters67Haller, Groza - Get on the Linked Data Web! (Meta 2011)FacebookRDFa in OpenGraph ProtocolApril 2010Any web page linked in the graph as a nodeSimple markup

RDFa adopters68Haller, Groza - Get on the Linked Data Web! (Meta 2011)[Adapted from Knud Moeller(DERI Galway), RDFa everywhere, 2010]

RDFa adopters69Haller, Groza - Get on the Linked Data Web! (Meta 2011)

RDFa adopters72Haller, Groza - Get on the Linked Data Web! (Meta 2011)<div typeof="austlit:Work" id="CMCg" about="#CMCg" property="austlit:topicID" content="CMCg"> The Drover’s Wife short story

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