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Semantic web: where are weSemantic web: where are we
now?now?
ADLUG Users Group MeetingADLUG Users Group Meeting
Bilbao, 1...
2 Semantic web: where are we
ContentsContents
TutorialTutorial
Where are we now?Where are we now?
3 Semantic web: where are we
Linked data on the webLinked data on the web
Use RDF data modelUse RDF data model
Use RDF l...
4 Semantic web: where are we
Advantage of Linked DataAdvantage of Linked Data
Linked Data provides a single,Linked Data p...
5 Semantic web: where are we
Web architecture : resourcesWeb architecture : resources
We have to identify the items of in...
6 Semantic web: where are we
Web architecture : resourcesWeb architecture : resources
identifiersidentifiers
 Uniform Res...
7 Semantic web: where are we
Web architecture : representationWeb architecture : representation
Information resources can...
8 Semantic web: where are we
Web architecture : dereferencingWeb architecture : dereferencing
HTTP URIHTTP URI
 This is t...
9 Semantic web: where are we
Web architecture : contentWeb architecture : content
negotiationnegotiation
 For non-informa...
http://nektar.oszk.hu/resource/manifestation/2645471http://nektar.oszk.hu/resource/manifestation/2645471
http://nektar.osz...
12 Semantic web: where are we
Web architecture : URI aliasesWeb architecture : URI aliases
 Two data provider can assign ...
13 Semantic web: where are we
Web architecture : AssociatedWeb architecture : Associated
descriptionsdescriptions
RDF des...
14 Semantic web: where are we
The RDF data modelThe RDF data model
RDF (Resource Description Framework)RDF (Resource Desc...
15 Semantic web: where are we
The RDF data modelThe RDF data model
ExampleExample
– The bookThe book has the titlehas the...
16 Semantic web: where are we
The RDF data modelThe RDF data model
SubjectSubject
– URI identifying the described resourc...
17 Semantic web: where are we
The RDF data modelThe RDF data model
Two types of RDF triplesTwo types of RDF triples
– Lit...
18 Semantic web: where are we
The RDF data modelThe RDF data model
 ExampleExample 11
– The bookThe book has the titlehas...
23 Semantic web: where are we
The RDF data modelThe RDF data model
The most valuable RDF links are thoseThe most valuable...
24 Semantic web: where are we
The RDF data modelThe RDF data model
Benefits of using the RDF data modelBenefits of using ...
25 Semantic web: where are we
Choosing URIsChoosing URIs
Good nameGood name
– ExpressiveExpressive
– Others can use confi...
26 Semantic web: where are we
Choosing URIsChoosing URIs
Good practice (Cool URIs)Good practice (Cool URIs)
– Use HTTP UR...
27 Semantic web: where are we
Choosing URIsChoosing URIs
Good practice (Cool URIs)Good practice (Cool URIs)
– Implementat...
28 Semantic web: where are we
Choosing URIsChoosing URIs
Good practice (Cool URIs)Good practice (Cool URIs)
– Try to keep...
29 Semantic web: where are we
VocabulariesVocabularies
 Well-known vocabulariesWell-known vocabularies
– Friend-of-a-Frie...
30 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
RequirementRequirement...
31 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
How to create external...
32 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
Serving the dataset as...
33 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
Serving relational dat...
34 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
Wrappers around existi...
35 Semantic web: where are we
Serving information as Linked DataServing information as Linked Data
RDF databaseRDF databa...
36 Semantic web: where are we
Testing and debuggingTesting and debugging
RDF browsersRDF browsers
– TabulatorTabulator
– ...
37 Semantic web: where are we
Discovering linked data on the webDiscovering linked data on the web
Ping the semantic webP...
38 Semantic web: where are we
Discovering linked data on the webDiscovering linked data on the web
Semantic Web Crawling:...
39 Semantic web: where are we
Web of data search enginesWeb of data search engines
FalconsFalcons developed by IWS Chinad...
40 Semantic web: where are we
Semantic web: where are we now?Semantic web: where are we now?
42 Semantic web: where are we
The model in detailThe model in detail
The thing URIThe thing URI
http://nektar.oszk.hu/res...
43 Semantic web: where are we
The model in detailThe model in detail
 Content negotiation rulesContent negotiation rules
...
44 Semantic web: where are we
The working modelThe working model
45 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
46 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
47 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
48 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
49 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
50 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
51 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
52 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
53 Semantic web: where are we
The record in LibriVisionThe record in LibriVision
54 Semantic web: where are we
SKOSSKOS
SKOS is now a W3C recommendationSKOS is now a W3C recommendation
– Last year it ju...
55 Semantic web: where are we
Useful linksUseful links
 How to Publish Linked Data on the WebHow to Publish Linked Data o...
adam@oszk.huadam@oszk.hu
Thank you for your attentionThank you for your attention
Semantic web: where are we now?
Semantic web: where are we now?
Semantic web: where are we now?
Semantic web: where are we now?
Semantic web: where are we now?
Semantic web: where are we now?
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Semantic web: where are we now?

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Introduction to semantic web. The first results in publication of library data into the semantic web at the National Széchényi Libary (National Library of Hungary)

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Semantic web: where are we now?

  1. 1. Semantic web: where are weSemantic web: where are we now?now? ADLUG Users Group MeetingADLUG Users Group Meeting Bilbao, 16-18 September, 2009Bilbao, 16-18 September, 2009 ÁdámÁdám HorváthHorváth NSZLNSZL
  2. 2. 2 Semantic web: where are we ContentsContents TutorialTutorial Where are we now?Where are we now?
  3. 3. 3 Semantic web: where are we Linked data on the webLinked data on the web Use RDF data modelUse RDF data model Use RDF linksUse RDF links Web of Data or Semantic WebWeb of Data or Semantic Web Linked Data browsersLinked Data browsers Linked Data provides a single,Linked Data provides a single, standardised access mechanismstandardised access mechanism (compared to APIs)(compared to APIs)
  4. 4. 4 Semantic web: where are we Advantage of Linked DataAdvantage of Linked Data Linked Data provides a single,Linked Data provides a single, standardised access mechanismstandardised access mechanism – Easily crawlableEasily crawlable – Accessible using generic data browserAccessible using generic data browserss – Enables link between data from differentEnables link between data from different data sourcesdata sources
  5. 5. 5 Semantic web: where are we Web architecture : resourcesWeb architecture : resources We have to identify the items of interestWe have to identify the items of interest in our domainin our domain All items of interest are calledAll items of interest are called resourcesresources – Information resources (everything in theInformation resources (everything in the traditional web)traditional web) – Non-information resources (real worldNon-information resources (real world objects, things)objects, things)
  6. 6. 6 Semantic web: where are we Web architecture : resourcesWeb architecture : resources identifiersidentifiers  Uniform Resource Identifiers (URIs)Uniform Resource Identifiers (URIs) HTTP URIHTTP URI – Not URN, DOI and so onNot URN, DOI and so on Why HTTP URIWhy HTTP URI – Simple way of creating globally uniqueSimple way of creating globally unique identifier without centralised managementidentifier without centralised management – Can also be used for accessing humanCan also be used for accessing human readable information (information on thereadable information (information on the Web)Web)
  7. 7. 7 Semantic web: where are we Web architecture : representationWeb architecture : representation Information resources can haveInformation resources can have representationsrepresentations Representations are stream of bytesRepresentations are stream of bytes A resource can have manyA resource can have many representationsrepresentations
  8. 8. 8 Semantic web: where are we Web architecture : dereferencingWeb architecture : dereferencing HTTP URIHTTP URI  This is the process of looking up URI on theThis is the process of looking up URI on the WEB to get information about the referencedWEB to get information about the referenced resourceresource  Information resourcesInformation resources – HTTP 200HTTP 200 „OK”„OK” response coderesponse code  Non-information resourcesNon-information resources – HTTP 303HTTP 303 „„SeeSee OOtherther”” reference codereference code – The client dereferences the new URI and getsThe client dereferences the new URI and gets representation describing the original non-representation describing the original non- information objectinformation object
  9. 9. 9 Semantic web: where are we Web architecture : contentWeb architecture : content negotiationnegotiation  For non-information resources it is aFor non-information resources it is a good practice to create an HTMLgood practice to create an HTML representation describing the thing forrepresentation describing the thing for human being and an RDFhuman being and an RDF representation for machinesrepresentation for machines The different representations can beThe different representations can be reached via the content negotiationreached via the content negotiation
  10. 10. http://nektar.oszk.hu/resource/manifestation/2645471http://nektar.oszk.hu/resource/manifestation/2645471 http://nektar.oszk.hu/data/manifestation/2645471http://nektar.oszk.hu/data/manifestation/2645471
  11. 11. 12 Semantic web: where are we Web architecture : URI aliasesWeb architecture : URI aliases  Two data provider can assign differentTwo data provider can assign different URI for the same resourceURI for the same resource – http://dbpedia.org/resource/Berlinhttp://dbpedia.org/resource/Berlin – http://sws.geonames.org/2950159/http://sws.geonames.org/2950159/ Information providers often setInformation providers often set owl:sameAsowl:sameAs link to URI aliases they know aboutlink to URI aliases they know about
  12. 12. 13 Semantic web: where are we Web architecture : AssociatedWeb architecture : Associated descriptionsdescriptions RDF description of a non-informationRDF description of a non-information object that a client obtains byobject that a client obtains by dereferencing the URI of the non-dereferencing the URI of the non- information objectinformation object
  13. 13. 14 Semantic web: where are we The RDF data modelThe RDF data model RDF (Resource Description Framework)RDF (Resource Description Framework) is used to represent information aboutis used to represent information about resourcesresources A description of a resource isA description of a resource is represented as a number of triplesrepresented as a number of triples Triples contain subject, predicate,Triples contain subject, predicate, objectobject
  14. 14. 15 Semantic web: where are we The RDF data modelThe RDF data model ExampleExample – The bookThe book has the titlehas the title DekameronDekameron – SubjectSubject PredicatePredicate ObjectObject
  15. 15. 16 Semantic web: where are we The RDF data modelThe RDF data model SubjectSubject – URI identifying the described resourceURI identifying the described resource ObjectObject – Literal value (string, number, date, etc)Literal value (string, number, date, etc) – URI that is related somehow to the subjectURI that is related somehow to the subject PredicatePredicate – Indicates the relationship between theIndicates the relationship between the subject and objectsubject and object – URI, and comes from vocabulariesURI, and comes from vocabularies
  16. 16. 17 Semantic web: where are we The RDF data modelThe RDF data model Two types of RDF triplesTwo types of RDF triples – Literal RDFLiteral RDF • Used to describe the properties of resourcesUsed to describe the properties of resources – The title of a bookThe title of a book – RDF linksRDF links • Three URIThree URI • Subject and Object identify the interlinkedSubject and Object identify the interlinked resourcesresources • Predicate tells the relationshipPredicate tells the relationship
  17. 17. 18 Semantic web: where are we The RDF data modelThe RDF data model  ExampleExample 11 – The bookThe book has the titlehas the title DekameronDekameron – SubjectSubject PredicatePredicate ObjectObject  Example 2Example 2 – SubjectSubject • http://nektar.oszk.hu/resource/manifestation/2645471http://nektar.oszk.hu/resource/manifestation/2645471 – PredicatePredicate • <dc:title><dc:title> – ObjectObject • DekameronDekameron
  18. 18. 23 Semantic web: where are we The RDF data modelThe RDF data model The most valuable RDF links are thoseThe most valuable RDF links are those that connect the resource to externalthat connect the resource to external data published by other data sourcesdata published by other data sources
  19. 19. 24 Semantic web: where are we The RDF data modelThe RDF data model Benefits of using the RDF data modelBenefits of using the RDF data model – Clients can lookup every URI in the RDFClients can lookup every URI in the RDF graph over the Web to retrieve additionalgraph over the Web to retrieve additional informationinformation – Information from different sources mergeInformation from different sources merge naturallynaturally – RDF links between data from differentRDF links between data from different sources can be setsources can be set – Information expressed in different schemaInformation expressed in different schema can be represented in a single modelcan be represented in a single model
  20. 20. 25 Semantic web: where are we Choosing URIsChoosing URIs Good nameGood name – ExpressiveExpressive – Others can use confidentlyOthers can use confidently Technical infrastructure to make themTechnical infrastructure to make them dereferencabledereferencable
  21. 21. 26 Semantic web: where are we Choosing URIsChoosing URIs Good practice (Cool URIs)Good practice (Cool URIs) – Use HTTP URIUse HTTP URI • Not URN, DOINot URN, DOI – Define URI in the namespace under yourDefine URI in the namespace under your controlcontrol
  22. 22. 27 Semantic web: where are we Choosing URIsChoosing URIs Good practice (Cool URIs)Good practice (Cool URIs) – Implementation specific things should notImplementation specific things should not appearappear – Compare:Compare: http://link.oszk.hu/libriurl.php?http://link.oszk.hu/libriurl.php? LN=hu&DB=OSZK&SRY=an&SRE=000002645471LN=hu&DB=OSZK&SRY=an&SRE=000002645471 http://nektar.oszk.hu/hu/manifestation/2645471http://nektar.oszk.hu/hu/manifestation/2645471
  23. 23. 28 Semantic web: where are we Choosing URIsChoosing URIs Good practice (Cool URIs)Good practice (Cool URIs) – Try to keep stable and persistentTry to keep stable and persistent
  24. 24. 29 Semantic web: where are we VocabulariesVocabularies  Well-known vocabulariesWell-known vocabularies – Friend-of-a-Friend (FOAF), vocabulary for describing people.Friend-of-a-Friend (FOAF), vocabulary for describing people. – Dublin Core (DC) defines general metadata attributes. See also theirDublin Core (DC) defines general metadata attributes. See also their new domains and ranges draft.new domains and ranges draft. – Semantically-Interlinked Online Communities (SIOC), vocabulary forSemantically-Interlinked Online Communities (SIOC), vocabulary for representing online communities.representing online communities. – Description of a Project (DOAP), vocabulary for describing projects.Description of a Project (DOAP), vocabulary for describing projects. – Simple Knowledge Organization System (SKOS), vocabulary forSimple Knowledge Organization System (SKOS), vocabulary for representing taxonomies and loosely structured knowledge.representing taxonomies and loosely structured knowledge. – Music Ontology provides terms for describing artists, albums andMusic Ontology provides terms for describing artists, albums and tracks.tracks. – Review Vocabulary, vocabulary for representing reviews.Review Vocabulary, vocabulary for representing reviews. – Creative Commons (CC), vocabulary for describing license terms.Creative Commons (CC), vocabulary for describing license terms.
  25. 25. 30 Semantic web: where are we Serving information as Linked DataServing information as Linked Data RequirementRequirement – Things must be identified with dereferenceableThings must be identified with dereferenceable HTTP URIsHTTP URIs – Data source must return an RDF/XMLData source must return an RDF/XML description of the identified resourcedescription of the identified resource – Links to external resourcesLinks to external resources – Links from external resources (ensure that thereLinks from external resources (ensure that there are external RDF links pointing at URIs fromare external RDF links pointing at URIs from your dataset)your dataset)
  26. 26. 31 Semantic web: where are we Serving information as Linked DataServing information as Linked Data How to create external links pointing to yourHow to create external links pointing to your data?data? – In your FOAF file point the central resources ofIn your FOAF file point the central resources of your datasetyour dataset • If one of your friends has a FOAF file and points toIf one of your friends has a FOAF file and points to you your dataset is now part of the Web of Datayou your dataset is now part of the Web of Data – Convince the owners of related data sets toConvince the owners of related data sets to auto-generate links to your datasetauto-generate links to your dataset
  27. 27. 32 Semantic web: where are we Serving information as Linked DataServing information as Linked Data Serving the dataset as static RDF fileServing the dataset as static RDF file – Which cases?Which cases? • RDF files are created manuallyRDF files are created manually • RDF files are created programs that produces fileRDF files are created programs that produces file outputoutput – HowHow • Give .rdf filename extensionGive .rdf filename extension • In httpd.conf add this lineIn httpd.conf add this line – AddType application/rdf+xml .rdfAddType application/rdf+xml .rdf – Problem: 303 redirect does not workProblem: 303 redirect does not work
  28. 28. 33 Semantic web: where are we Serving information as Linked DataServing information as Linked Data Serving relational databasesServing relational databases – D2R serverD2R server • Provides a SPARQL endpoint to the relationalProvides a SPARQL endpoint to the relational database by the means of mapping filedatabase by the means of mapping file
  29. 29. 34 Semantic web: where are we Serving information as Linked DataServing information as Linked Data Wrappers around existing applications andWrappers around existing applications and WEB APIWEB API – RDF Book MashupRDF Book Mashup • The RDF Book Mashup assigns a HTTP URI to eachThe RDF Book Mashup assigns a HTTP URI to each book that has an ISBN numberbook that has an ISBN number • Whenever the HTTP URI is dereferenceWhenever the HTTP URI is dereferencedd RDF BookRDF Book Mashup requires data from Amazon API and GoogleMashup requires data from Amazon API and Google Base APIBase API
  30. 30. 35 Semantic web: where are we Serving information as Linked DataServing information as Linked Data RDF databaseRDF database – JenaJena • SPARQL endpoint is JoSPARQL endpoint is Josekiseki
  31. 31. 36 Semantic web: where are we Testing and debuggingTesting and debugging RDF browsersRDF browsers – TabulatorTabulator – MarblesMarbles – Open Link RDF BrowserOpen Link RDF Browser – DiscoDisco Testing dereferencingTesting dereferencing – curlcurl W3C RDF validation serviceW3C RDF validation service
  32. 32. 37 Semantic web: where are we Discovering linked data on the webDiscovering linked data on the web Ping the semantic webPing the semantic web – Registry service for RDF documentsRegistry service for RDF documents HTML link auto-discoveryHTML link auto-discovery – Set links from existing web pages to RDF dataSet links from existing web pages to RDF data – HTML <link> element in the <head> of yourHTML <link> element in the <head> of your HTML pageHTML page – <link rel="alternate" type="application/rdf+xml"<link rel="alternate" type="application/rdf+xml" href="link_to_the_RDF_version"/>href="link_to_the_RDF_version"/>
  33. 33. 38 Semantic web: where are we Discovering linked data on the webDiscovering linked data on the web Semantic Web Crawling: a SitemapSemantic Web Crawling: a Sitemap ExtensionExtension – Data publishers can state where RDF is locatedData publishers can state where RDF is located – Robot.txtRobot.txt Dataset List on the ESW WikiDataset List on the ESW Wiki
  34. 34. 39 Semantic web: where are we Web of data search enginesWeb of data search engines FalconsFalcons developed by IWS Chinadeveloped by IWS China SindiceSindice developed by DERI Irelanddeveloped by DERI Ireland WatsonWatson developed by KMi, UKdeveloped by KMi, UK Semantic Web Search Engine (SWSE)Semantic Web Search Engine (SWSE) developed by DERI Irelanddeveloped by DERI Ireland SwoogleSwoogle developed by ubiquity group atdeveloped by ubiquity group at UMBC USAUMBC USA
  35. 35. 40 Semantic web: where are we Semantic web: where are we now?Semantic web: where are we now?
  36. 36. 42 Semantic web: where are we The model in detailThe model in detail The thing URIThe thing URI http://nektar.oszk.hu/resource/manifestation/2645471http://nektar.oszk.hu/resource/manifestation/2645471 – The 303 redirection code indicates that this URI is for thingThe 303 redirection code indicates that this URI is for thing The RDF document URIThe RDF document URI http://nektar.oszk.hu/data/manifestation/2645471http://nektar.oszk.hu/data/manifestation/2645471  The WEB (LibriVision) document URIThe WEB (LibriVision) document URI http://nektar.oszk.hu/http://nektar.oszk.hu/huhu/manifestation/2645471/manifestation/2645471 http://nektar.oszk.hu/http://nektar.oszk.hu/enen/manifestation/2645471/manifestation/2645471
  37. 37. 43 Semantic web: where are we The model in detailThe model in detail  Content negotiation rulesContent negotiation rules – If application/rdf+xml is accepted the xml is givenIf application/rdf+xml is accepted the xml is given from this address via content negotiation and 303from this address via content negotiation and 303 redirect:redirect: http://nektar.oszk.hu/data/manifestation/2645471http://nektar.oszk.hu/data/manifestation/2645471 – If text/html is acceptedIf text/html is accepted • Depending on the language of the browser either theDepending on the language of the browser either the Hungarian or the English interface of LibriVision is given.Hungarian or the English interface of LibriVision is given. The default is Hungarian (again via content negotiation):The default is Hungarian (again via content negotiation): http://nektar.oszk.hu/hu/manifestation/2645471http://nektar.oszk.hu/hu/manifestation/2645471
  38. 38. 44 Semantic web: where are we The working modelThe working model
  39. 39. 45 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  40. 40. 46 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  41. 41. 47 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  42. 42. 48 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  43. 43. 49 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  44. 44. 50 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  45. 45. 51 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  46. 46. 52 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  47. 47. 53 Semantic web: where are we The record in LibriVisionThe record in LibriVision
  48. 48. 54 Semantic web: where are we SKOSSKOS SKOS is now a W3C recommendationSKOS is now a W3C recommendation – Last year it just was a proposedLast year it just was a proposed recommendationrecommendation NSZL is among the first implementersNSZL is among the first implementers
  49. 49. 55 Semantic web: where are we Useful linksUseful links  How to Publish Linked Data on the WebHow to Publish Linked Data on the Web – http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/  Cool URIs for the Semantic WebCool URIs for the Semantic Web – http://www.w3.org/TR/2008/NOTE-cooluris-20080331/http://www.w3.org/TR/2008/NOTE-cooluris-20080331/  SKOS Simple Knowledge Organization SystemSKOS Simple Knowledge Organization System ReferenceReference – http://www.w3.org/TR/skos-reference/http://www.w3.org/TR/skos-reference/  SKOS Simple Knowledge Organization System PrimerSKOS Simple Knowledge Organization System Primer – http://www.w3.org/TR/skos-primer/http://www.w3.org/TR/skos-primer/  SKOS implementation reportSKOS implementation report – http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/implehttp://www.w3.org/2006/07/SWD/SKOS/reference/20090315/imple mentation.htmlmentation.html
  50. 50. adam@oszk.huadam@oszk.hu Thank you for your attentionThank you for your attention

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