1. The Semantic Web Web Science Systems Development Spring 2015

2. Agenda History / Background Linked Data RDF SPARQL OWL Applications Current state of the Semantic Web

3. The Web Core Principles Standard for identifying resources Standard for representing resources Standard for exchanging resources

4. The Web Core Principles Standard for identifying resources Standard for representing resources Standard for exchanging resources Standards: URIs (URLs): Uniform Resource Identifier (Locator) HTML: Hypertext Markup Language HTTP: Hypertext Transfer Protocol

5. URI Identifies one resource A resource could be anything URIs are persistent URLs also locate and are aligned with protocols URLs are dereferenceable URLs mailto:joe@example.org ftp://example.org/aDirectory/aFile ldap://ldap.example.org/c=GB?objectClass?one

6. HTML It is not the resource Serialization of information A resource can have multiple representations Manifestation of the resource as a digital document Retrievable resources: Encode data and information Link to other resources (creating the “Web”)

7. HTTP Protocol for information exchange on the web Protocol is specified in the URL Used for client-server communication (request- response protocol) Structured text (header, body,…) Currently at http/1.1 (since 1999), http/2 in draft form

8. One Web

9. Principles of a healthy web Identify resources using URIs Use HTTP in URIs so that people can look up resources When someone looks up a resource, return useful information (using standard representation e.g. HTML) Link to other URIs

10. Linking Asserts relevance/quality of page Allows discovery Creates the “Web” effect

11. The Semantic Web What is it? Semantics, knowledge representation, ontologies and agents.

13. Linked Data From the web of documents to the web of data

14. Documents VS. Data

15. Web of documents HTML Data HTML Data HTML Data HTML Data HTML Data

16. Web of data Data

17. One Web

18. RDF Resource Description Framework

19. Semantic Web Stack

20. RDF: Resource Description Framework The triple SubjectObject Predicate

21. RDF: Resource Description Framework The triple SubjectObject Predicate “WebSci”“Ahmed” “hasTA”

22. RDF Triple SubjectPredicate Object IRI Literal Resource denotes Blank Node representedBy

23. RDF triple “article” “James Hendler” “hasCreator” http://dx.doi.org//10.110 9/MC.2009.30 http://dbpedia.org/resourc e/James_Hendler http://purl.org/dc/eleme nts/1.1/creator

24. RDF A triple is true if the relationship holds between the subject and the object Resource Can be ‘anything’, including documents, people, physical objects, and abstract concepts IRI: Internationalized Resource Identifier IRIs conform to Universal Character Set, not just ASCII IRIs are global, dereferenceable and persistent Blank nodes are anonymous resources

25. RDF Graph-based Data Model Visualized as diagram of nodes and directed-arcs Nodes represent ‘entities’ and are resources Arcs represent relationships between the nodes and are also resources RDF Graph consists of a set of triples

26. RDF Graph

27. Raw RDF

28. RDF Serializations (representations) Multiple serializations RDF/XML JSON-LD Turtle family Turtle N3 Trig

29. RDF/XML

30. JSON-LD

31. N3

32. RDFa

33. Querying RDF How to retrieve linked data? How and where to query RDF graphs?

34. SPARQL SPARQL Protocol and RDF Query Language

35. Semantic Web Stack

36. SPARQL Language for querying RDF Triplestores and endpoints Queries consist of triple patterns, conjunctions, disjunctions and optional patterns SPARQL is a protocol that defines how an endpoint responds to a query

37. SPARQL query (basic) PREFIX geo: PREFIX geof: PREFIX sf: PREFIX vocab: PREFIX rdfs: PREFIX rpi: SELECT DISTINCT ?professor ?course ?building WHERE { ?prof a rpi:Professor. ?course rpi:instructedBy ?professor. ?course rpi:courseTitle ?title. ?course rpi:hostedInBuilding ?building. ?building rdfs:label ?label. FILTER regex(?title,"WEB") } Namespaces Patterns to match Filter Variables

38. SPARQL query result

39. SPARQL query (complex) Federated query + GeoSPARQL PREFIX geo: PREFIX geof: PREFIX sf: PREFIX vocab: PREFIX rdfs: PREFIX rpi: SELECT DISTINCT ?professor ?course ?building WHERE { ?course vocab:rpi_class_schedule_all_building_id ?building. SERVICE { ?professor a rpi:Professor. ?course rpi:instructedBy ?professor. ?building rdfs:label ?label. ?building geo:hasGeometry ?geo. ?geo geo:asWKT ?xy FILTER(geof:sfIntersects(?xy,"POINT(-73.681948 42.730076)" ^^ )) }} ‘Remote’ Endpoint GeoSPARQL Function

40. SPARQL query (complex) result

41. SPARQL query (inference) PREFIX rdf: PREFIX rdfs: PREFIX rpi: PREFIX foaf: SELECT ?s WHERE { ?s a rpi:Person. ?s foaf:knows } Superclass

42. SPARQL query (inference) result

43. OWL Web Ontology Language

44. Semantic Web Stack

45. Web Ontology Language Provides semantics/structure to RDF Computational logic-based language, allows reasoning by computer programs to: Verify consistency of knowledge Make implicit knowledge explicit Enables inference of new triples from existing ones Used to build ontologies/vocabularies Rules that constrain relationships between entities in a domain

46. OWL basic notions Axioms Entities Expressions

47. OWL components Class hierarchies Object properties Property hierarchies Domain & range restrictions Datatypes

48. RPI Campus Ontology

49. Ontology Engineering ExpressivityImplementation Maintenance QueryRules Infer

50. Applications of Linked Data

51. Linking related data Websites with related data on different platforms

52. Linking related data Websites with related data on different platforms RDB Website A Website B Triplstore Mapping File RDF SPARQL-to- SQL Direct Mapping XML XSLT

53. RPI campus map application Map of the RPI campus with clickable features (buildings, emergency callboxes,…etc.) Geolocation data in KML for projection and in RDF for GeoSPARQL queries Class schedule scraped off SIS in RDBMS Mapping of schedule to RDF for SPARQL queries

54. Campus map KML

55. Campus map RDF

56. Class schedule

57. RPI campus map application HTML/JavaScript front-end PHP back-end OpenLayers 3 mapping API OpenStreetMap tiles Class schedule csv loaded into MySQL D2RQ server mapping MySQL to RDF Map data RDF loaded into Parliament triplestore

58. RPI Campus Map

59. Current state of the Semantic Web

60. Evolution of the web

61. Linked Open Data (2007)

62. Linked Open Data (2008)

63. Linked Open Data (2009)

64. Linked Open Data (now)

65. Open linked data

66. References Tim Berners Lee’s proposal - http://info.cern.ch/Proposal.htmlhttp://info.cern.ch/Proposal.html W3C web architecture - http://www.w3.org/TR/webarch/http://www.w3.org/TR/webarch/ W3C Technology Stack - http://www.w3.org/Consortium/techstack-desc.htmlhttp://www.w3.org/Consortium/techstack-desc.html Google PageRank - http://en.wikipedia.org/wiki/PageRankhttp://en.wikipedia.org/wiki/PageRank Scientific American – The Semantic Web -http://www.cs.umd.edu/~golbeck/LBSC690/SemanticWeb.htmlhttp://www.cs.umd.edu/~golbeck/LBSC690/SemanticWeb.html RDF – Resource Description Framework - http://www.w3.org/TR/rdf11-concepts/http://www.w3.org/TR/rdf11-concepts/ SPARQL – SPARQL Protocol & RDF Query Language - http://www.w3.org/TR/sparql11-protocol/http://www.w3.org/TR/sparql11-protocol/ OpenStreetMap - http://www.openstreetmap.org/http://www.openstreetmap.org/ Parliament Triplestore - http://parliament.semwebcentral.org/http://parliament.semwebcentral.org/ D2R Server - http://d2rq.org/http://d2rq.org/ Linked Open Data - http://lod-cloud.net/http://lod-cloud.net/