Semantic Web: an introduction
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Short seminar about the Semantic Web for the "Artificial Intelligence" course at Politecnico di Torino (academic year 2012/2013) An updated version is available at http://www.slideshare.net/luigidr/semantic-web-an-introduction
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Semantic Web: an introduction
- 1. THE SEMANTIC WEB AN INTRODUCTION LUIGI DE RUSSIS
- 2. THE WEB IS A WEB OF DOCUMENT FOR PEOPLE,NOT FOR MACHINES
- 3. THE SEMANTIC WEB IS A WEB OF DATA LinkingOpen Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/
- 4. LET’S THINK!
- 5. EXERCISE:BUILD A MUSIC CATALOG Comprehensive guidetomusicacrosstheworld Web-based Withalways-updatedinformationabouteachartist
- 6. HOW? WHAT ARE THE PROBLEMS? WHAT ABOUT DATA REPLICATION? WHAT ABOUT DATA SYNCHRONIZATION? …?
- 7. SOLUTION #1 HOW? SiteeditorsroamtheWebfornewfactsandupdatethesitemanually WHAT ARE THE PROBLEMS? AlotofpeopleneedtocontinuouslyroamtheWeb;thesitewillget soonout-of-date WHAT ABOUT DATA? Dataisreplicatedandnotup-to-datewithnewfacts
- 8. SOLUTION #2 HOW? SiteeditorsroamtheWebfornewdataandwriteaprogramtoextract theinformation WHAT ARE THE PROBLEMS? Codeneedstobeupdatedeachtimeanewsiteisfound;the sitewillget out-of-date,soonorlater… WHAT ABOUT DATA? Dataisreplicatedandnotup-to-date
- 9. SOLUTION #3 HOW? SiteeditorsbrowsetheWebfornewdataviaAPIs,andwritesomecode toincorporatetheinformation WHAT ARE THE PROBLEMS? Codeneedstobeupdatedeachtimeanewsiteisfoundand/oranAPIis changed;thesitewillgetout-of-date,soonorlater… WHAT ABOUT DATA? Dataisreplicatedandnotup-to-date
- 10. SOLUTION #4 HOW? Siteeditorschoosetousesomeexternal,publicdatasets(e.g., Wikipedia,MusicBrainz,…) WHAT ARE THE PROBLEMS? Noproblem WHAT ABOUT DATA? Dataisimmediatelyavailable,notasAPIsorhiddenonaWebsite. InformationcanbeextractedusingstandardqueriesorHTTPrequests.
- 12. DATA ON THE WEB IS NOT ENOUGH! weneedaproperinfrastructure DATA SHOULD BE AVAILABLE ON THE WEB accessibleviastandardWebtechnologies DATA SHOULD BE INTERLINKED OVER THE WEB i.e.,datacanbeintegratedovertheWeb THIS IS WHERE SEMANTIC WEB COME IN
- 13. FUNDAMENTALS
- 14. To a computer,theWeb is a flat,boring world, devoid of meaning. This is a pity, as in factdocumentson theWeb describereal objects and imaginary concepts.[…] Adding semanticstothe Web involvestwothings: allowing documents which have informationin machine-readable forms, and allowing links tobe createdwith relationship values. Only when we have this extra level of semanticswe will be able touse computerpower tohelp us exploit the information toa greaterextent than our own reading. TIM BERNERS-LEE,1994
- 15. WHAT IS THE RELATIONSHIP WITH AI? INFLUENCE SometechnologiesintheSemanticWebbenefitedalotfromAIresearch anddevelopment(andviceversa) DIFFERENT GOALS ArtificialIntelligenceapproach:buildsmartermachines,teach computerstoinferthemeaningofdata SemanticWebapproach:havesmarterdata,makedataeasierfor machinestofind,accessandprocess
- 16. RESOURCE AND DESCRIPTION RESOURCE everydocument“reachable”ontheWeb nomatterthecontent,format,language,etc. RESOURCE DESCRIPTION independentfromtheformat standardlanguage(metadata)
- 19. RESOURCE AND DESCRIPTION DescriptionTitle Author Date Topic Quality Title Author Date Topic
- 21. MODELING DATA
- 24. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Literal
- 25. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach title
- 26. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall Russel, Stuart Norvig, Peter title publisher author author
- 27. RDF:RESOURCE DESCRIPTION FRAMEWORK STRUCTURED IN STATEMENTS SUBJECT aresource(URI) PREDICATE averb,propertyorrelationship OBJECT aresourceoraliteralstring
- 28. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall Russel, Stuart Norvig, Peter title publisher author author Subject Object Object Object Object Predicate Predicate Predicate
- 29. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach title RDFIN XMLSYNTAX <rdf:RDFxmlns:rdf=http://www.w3.org/…/22-rdf-syntax-ns#> <rdf:Descriptionabout=“http://...isbn/9780136042594”> <title>ArtificialIntelligence:AModernApproach</title> </rdf:Description> </RDF>
- 30. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach title RDFIN TURTLE <http://...isbn/9780136042594> title“ArtificialIntelligence:AModernApproach”
- 31. LINKIN’DATA
- 33. EXAMPLE:BOOKSTORE http://...isbn/9788871925936 Intelligenza Artificiale. Un approccio moderno Prentice Hall Russel, Stuart Norvig, Peter title publisher creator creator http://...isbn/9780136042594 original
- 34. EXAMPLE:BOOKSTORE http://...isbn/9788871925936 Intelligenza Artificiale. Un approccio moderno Prentice Hall title publisher http://...isbn/9780136042594 original http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall title publisher
- 35. EXAMPLE:BOOKSTORE http://...isbn/9788871925936 Intelligenza Artificiale. Un approccio moderno Prentice Hall title publisher http://...isbn/9780136042594 original http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall title creator sameURI,sameresource
- 36. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall Russel, Stuart Norvig, Peter title publisher author author http://...isbn/9788871925936 Intelligenza Artificiale. Un approccio moderno Prentice Hall title publisher original Russel, Stuart Norvig, Peter creator creator
- 37. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall Russel, Stuart Norvig, Peter title publisher author author http://...isbn/9788871925936 Intelligenza Artificiale. Un approccio moderno Prentice Hall title publisher original Russel, Stuart Norvig, Peter creator creator Whataboutmergingcreatorandauthor? InRDF,itisnotpossible!
- 38. PROBLEM:FIELD NAMES ARE ARBITRARY Synonyms:authororcreatorormakerorcontributoror… Singularorplural:authororauthors SOLUTION:STANDARDS generalordomain-specific
- 39. DUBLIN CORE GENERAL VOCABULARY DublinCoreMetadataInitiative(DCMI) http://dublincore.org BUILDING BLOCKS TO DEFINE METADATA FOR THE SEMANTIC WEB Definetitle,contributor,publisher,license,date,language,etc.
- 40. PROBLEM:FIELD VALUES ARE ARBITRARY Valuetype:string,date,integer,… Valueformat:“Norvig,Peter”or“Norvig,P.”or“PeterNorvig”or… Valuerestrictions:onevalueormultiplevalues(howmany?) SOLUTIONS Standards Controlledvocabulary(closelistofterms) Semanticallyrichdescriptionstosupportsearch(RDFSand/orOWL)
- 41. FRIEND OF AFRIEND (FOAF) GENERAL ONTOLOGY Describepersons,theiractivitiesandtheirrelationstootherpeopleand objects http://www.foaf-project.org BUILDING BLOCKS TO DEFINE STRUCTURED RELATIONS BETWEEN PEOPLE Definename,familyName,givenName,knows,age,nick,etc.
- 42. EXAMPLE:BOOKSTORE http://...isbn/9780136042594 Artificial Intelligence: A Modern Approach Prentice Hall Russel, Stuart Norvig, Peter dc:title dc:publisher dc:creator dc:creator foaf:http://xmlns.com/foaf/spec dc:http://purl.org/dc/terms foaf:name foaf:name foaf:name
- 44. RDFSCHEMA
- 48. http://...isbn/9780136042594 Norvig, Peter dc:creator foaf:name http://...isbn/9780136042594 Norvig, Peter author BACK TO THE BOOKSTORE EXAMPLE…
- 49. http://...isbn/9780136042594 Norvig, Peter dc:creator foaf:name http://...isbn/9780136042594 Norvig, Peter author BACK TO THE BOOKSTORE EXAMPLE… dc:creatorhasrangeAgent,i.e.aclass(resource),notaliteral: weuseananonymousclassforthisscope. Finally,foaf:Namehasrangerdfs:Literal. anonymous class
- 50. RDFSEXPRESSIVITY SIMPLE RELATIONSHIP BETWEEN THINGS RDFSprovidesavocabularytoexpressrelationshipbetweenthings (e.g.,subClassOfortype) AVOID COMPLEX RELATIONSHIP RDFScannotdescribedataintermsofsetofoperations(e.g., unionOf), equivalence(e.g.,sameAs)orcardinality(e.g.,allValueFrom)
- 51. OWL
- 53. WEB ONTOLOGY LANGUAGE INDIVIDUALS,CLASSES AND PROPERTIES “PolitecnicodiTorinoisauniversity” “PolitecnicodiTorinohasaprofessornamedElioPiccolo” “PolitecnicodiTorino”isaobject:anindividualinOWL2 “university”isacategory:aclassinOWL2 “hasaprofessor”isarelation:apropertyinOWL2 “ElioPiccolo”isanindividual,too
- 55. WEB ONTOLOGY LANGUAGE LINKED OntologiesinOWLcanbepublishedontheWebandmay referorbe referredfromotherOWLontologies CHOOSE THE SYNTAX YOU LIKE VarioussyntaxesavailableforOWL,fordifferentpurposes (RDF/XML,Turtle,Manchester,etc.)
- 56. EXAMPLE:BOOKSTORE Intelligenza Artificiale. Un approccio moderno Prentice Hall dc:title dc:publisher Artificial Intelligence: A Modern Approach Prentice Hall dc:title dc:publisher Libro Book rdfs:type rdf:type owl:sameAs http://...isbn/9788871925936 http://...isbn/9780136042594
- 57. HANDS ON OWL
- 60. DESCRIBE THE BUSINESS ENTITY default:BookStore_1 agr:BusinessEntity; gr:legalName“bookstore.comLtd.”^^xsd:string. Bookstore_1
- 61. DESCRIBE THE OFFERED ITEMS default:AIBook_en aitem:Book,gr:ActualProductOrServiceInstance ; item:hasTotalPagesdefault:QuantitativeValueInteger_1. AIBook_en default:QuantitativeValueInteger_1 agr:QuantitativeValueInteger; gr:hasValue“1132”^^xsd:integer. QuantitativeValue Integer_1
- 62. DESCRIBE THE OFFER default:Offering_1 agr:Offering ; gr:hasBusinessFunctiongr:Sell; gr:hasPriceSpecificationdefault:UnityPriceSpecification_1; gr:includeObjectdefault:TypeAndQuantityNode_1. Offering_1 LINK THE OFFER TO THE BUSINESS ENTITY default:BookStore_1gr:offersdefault:Offering_1
- 63. DESCRIBE THE OFFER default:TypeAndQuantityNode_1 agr:TypeAndQuantityNode ; gr:amountOfThisGood“1.0”^^xsd:float; gr:typeOfGooddefault:AIBook_en. default:UnitPriceSpecification_1 agr:UnitPriceSpecification; gr:hasCurrency“EUR”^^xsd:string; gr:hasCurrencyValue “120.0”^^xsd:float. TypeAndQuantity Node_1 UnitPriceSpecification_1