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The Semantic Web

The Semantic Web. Nottingham University 23 March 2007. The Official Definition. http://www.w3.org/2001/sw/.

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The Semantic Web

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  1. The Semantic Web Nottingham University 23 March 2007

  2. The Official Definition http://www.w3.org/2001/sw/ Definition: The Semantic Web is the representation of data on the World Wide Web. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF), which integrates a variety of applications using XML for syntax and URIs for naming.

  3. Semantic Web

  4. Semantic

  5. Semantic = Meaning ?

  6. Description The Semantic Web • HTML for presentation • XML for data • RDF for meaning A new form of Web content that is meaningful to computers will unleash a revolution of new possibilities…

  7. or…

  8. Semantic = Data Modelling

  9. Semantic Web is about data modelling • To make computers useful they must interact with the real world • So they must model the real world in some way • UML/Object Oriented; classes, instances, attributes • Relational (databases); tables, keys, constraints, schema • XML; documents, semistructured information, schema • Semantic Web uses RDF – with some similarities (and some differences) to these other techniques

  10. Semantic Web is about data modelling • The base level of RDF is the triple: {subject, predicate, object} • Examples {[I], rdf:type, foaf:Person} {[I], foaf:name, “Michael Souris”} {[I], foaf:mbox,mailto:mm@example.com} • And {foaf:name, rdf:type, rdf:Property}

  11. RDF triples define a graph data structure foaf:Person rdf:type foaf:name Michael Souris foaf:mbox mailto:mm@example.com

  12. .. which can be serialized in XML <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/"> <foaf:Person> <foaf:name>Michael Souris</foaf:name> <foaf:mbox rdf:resource="mailto:mm@example.com" /> </foaf:Person> </rdf:RDF>

  13. .. and N3 @prefix rdf <http://www.w3.org/1999/02/22-rdf-syntax-ns#> @prefix foaf <http://xmlns.com/foaf/0.1/> [] a foaf:Person; foaf:name “Michael Souris”; foaf:mbox <mailto:mm@example.com> .

  14. Web

  15. Merging RDF data from different sources Media metadata database: ../presentation.ppt dc:creator dc:date dc:description Talk on Semantic Web org:email 2006-04-23 mailto:steve.cayzer@hp.com

  16. The second datasource Organization database: org:Engineer rdf:type vcard:FN Steve Cayzer org:worksOn org:email ex:SemanticBlogging mailto:steve.cayzer@hp.com

  17. Two datasources merged Merged database: org:Engineer ../presentation.ppt rdf:type dc:creator vcard:FN dc:date dc:description Steve Cayzer org:worksOn Talk on Semantic Web org:email ex:SemanticBlogging 2006-04-23 mailto:steve.cayzer@hp.com

  18. Linking foaf profiles … foaf:Person rdf:type foaf:name Michael Souris foaf:mbox mailto:mm@example.com

  19. … into a social network … foaf:Person foaf:Person rdf:type rdf:type foaf:name foaf:name foaf:knows Michael Souris Donald Canard foaf:mbox foaf:mbox mailto:dd@example.com mailto:mm@example.com

  20. … and serialized for machines … <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/"> <foaf:Person> <foaf:name>Michael Souris</foaf:name> <foaf:mbox rdf:resource="mailto:mm@example.com" /> <foaf:knows> <foaf:Person> <foaf:mbox rdf:resource="mailto:dd@example.com" /> <foaf:name>Donald Canard</foaf:name> </foaf:Person> </foaf:knows> </foaf:Person> </rdf:RDF>

  21. .. or visualised by people The Friend of a Friend (FOAF) project is about creating a Web of machine-readable homepages describing people, the links between them and the things they create and do. Distributed RDF/XML records describing people, who they know, projects they work on…

  22. Semantic Web is also about global sharing of models • share data but also share models (or vocabularies) • Properties and Classes have URIs (so we can specify their semantics: ‘knows’ = met/friend/emailed/aware_of) • URIs must be globally unique (can use URLs) • Many shareable models eg documents (dublin core), images (EXIF!), people (foaf), lifesciences (ways of talking about genes, proteins), museums (items), • Modelling is not new; what’s new is that we can share models globally and mix them up – eg ‘find me photos (image metadata) about my friends (social network)’

  23. The Fractal Semantic Web • From http://www.w3.org/2005/Talks/1110-iswc-tbl/

  24. Technology

  25. Modelling language for data (and metadata) Universal (web-based) naming scheme Semantic Web Technologies Trust Proof Rules and logic Digital Signature Query OWL and RDFS RDF XML + Namespaces + xmlschema URI

  26. Ontology languages for representing the semantics of data Modelling language for data (and metadata) Universal (web-based) naming scheme Semantic Web Technologies Trust Proof Rules and logic Digital Signature Query OWL and RDFS RDF XML + Namespaces + xmlschema RDF, RDFS, OWL standardised February 2004 URI

  27. Semantic Web Ontology Languages RDFS Student is a subclass of Person friend is a subproperty of knows The domain and range of knows is Person OWL Lions only eat meat The ‘ancestor’ relationship is transitive People have exactly one shoesize An email address unambiguously identifies one person

  28. Ways of transforming data between ontologies Current research areas Query and data access protocol Ontology languages for representing the semantics of data Modelling language for data (and metadata) Universal (web-based) naming scheme Semantic Web Technologies Trust Proof Rules and logic Digital Signature Query OWL and RDFS RDF XML + Namespaces + xmlschema URI RDF, RDFS, OWL standardised Feb 2004 SPARQL query language: W3C Working Draft 4 October 2006 Rule Interchange Format working group chartered 2005

  29. Examples

  30. Aktors Integration of distributed… • RAE Data • Geographical Location • ACM Taxonomy • Internal Research Data • … http://www.aktors.org/akt/ http://triplestore.aktors.org/SemanticWebChallenge/

  31. An HP Example The Semantic Web Environmental Directory (SWED) is a prototype of a new kind of directory of environmental organisations and projects. Our goal is to develop a sustainable (realistically maintainable) and easy to use directory about environmental organisations and projects throughout the UK.www.swed.org.uk

  32. Conclusions

  33. A side note on XML • RDF is not XML (though it can be expressed in XML) • The semantic web is about global sharing of information models • RDF describes the information model • RDF can be expressed in XML (or N3, or drawn as a graph…) • XML Schema is all about syntax and so has limited use for RDF • RDF Schema is all about the model

  34. Take home messages • The semantic web is about globally sharing, processing and integrating information. • RDF is a model. • RDF is not XML, though it may be serialized in XML • Semantic web technologies range from production ready (the lower layers) to active research areas (the upper layers)

  35. Tutorials Official page: http://www.w3.org/2001/sw/ • Sean Palmer – programmers intro (2001) dated but quite nicehttp://infomesh.net/2001/swintro/ • Morbus Iff (creator of Amphetadesk) “The Semantic Web 1-2-3” good overviewhttp://disobey.com/detergent/2002/sw123/ • My introductory lecture (XML biased)http://www.hpl.hp.com/personal/Steve_Cayzer/downloads/040312_semweb_public_version.pdf

  36. Resources – interviews and presentations • W3C list http://www.w3.org/2001/sw/#events • Sir Tim Berners-Lee interview September 2004http://www.internetnews.com/dev-news/article.php/340962 • Tom Passin interview August 2004http://www.javaranch.com/journal/200408/Journal200408.jsp#a2 • Aaron Swartz interview January 2004 http://iron.wootest.net/aaron_swartz.php • Eric Miller (W3C semantic web activity lead) talk, early 2004http://www.w3.org/2004/Talks/0120-semweb-umich/slide1-0.html • The Semantic Web, Tim Berners-Lee 2002

  37. Resources – the controversy • Mark H Butler Is the Semantic Web Hype? Manchester Metropolitan University, 12th March 2003. Highlights some perceived difficulties ahead. • “Themes and metaphors in the semantic web discussion”November 15, 2003, Peter Van Dijckhttp://www.poorbuthappy.com/ease/semantic/Summarises the Clay Shirky article quoted earlier: “The Semantic Web, Syllogism, and Worldview” 2003http://www.shirky.com/writings/semantic_syllogism.html • “A no-nonsense guide to Semantic Web specs for XML people (Part I)” July 14, 2004 Stefano Mazzocchihttp://www.betaversion.org/~stefano/linotype/news/57/ (also serves as a tutorial) • Collaborative knowledge gardening August 2004 Jon Udell http://www.infoworld.com/article/04/08/20/34OPstrategic_1.htmlDo we actually need an ontology? • Curing the Web's Identity Crisis 2003 Steve Pepper http://www.ontopia.net/topicmaps/materials/identitycrisis.htmlThe problems with URIs

  38. Resources - books • “The Explorer’s Guide to the semantic web” Tom Passin (2004). Probably the best introductory bookhttp://www.manning.com/passin • “Practical RDF” Shelley Powers (2003)RDF/XML focused but well written and highly recommended http://www.oreilly.com/catalog/pracrdf/ • The Semantic Web: A Guide to the Future of XML, Web Services and Knowledge Management Michael C. Daconta et al. http://www.amazon.co.uk/exec/obidos/ASIN/0471432571/

  39. Resources - articles • W3C articles http://www.w3.org/2001/sw/#pub • The Semantic Web, Scientific American, May 2001, Tim Berners-Lee, James Hendler and Ora Lassila • Integrating applications on the Semantic WebJim Hendler, Tim Berners-Lee and Eric Miller, Journal IEE Japan, 122(10):676-680, 2002. • IEEE data engineering bulletin December 2003: Special Issue on Making the Semantic Web Real • Uncle Sam's Semantic Webby Paul Fordxml.com article, September 15, 2004http://www.xml.com/pub/a/2004/09/15/egov.html http://www.google.com

  40. Resources – programming • RDF primerhttp://www.w3.org/TR/2004/REC-rdf-primer-20040210/ • N3 primerhttp://www.w3.org/2000/10/swap/Primer and http://www.w3.org/2000/10/swap/doc/ • OWL guidehttp://www.w3.org/TR/2004/REC-owl-guide-20040210/ • Jena – the ‘swiss army knife’ of the semantic web, produced by Hewlett-Packard Laboratories in Bristol and Palo Altohttp://www.hpl.hp.com/semweb/jena.htm[Try the Jena tutorial for an introduction to semweb development]http://jena.sourceforge.net/tutorial/RDF_API/index.html • Protégé – Easy ontology creation, from Stanford Universityhttp://protege.stanford.edu/

  41. Resources – online demos • TAP – semantically assisted Google!http://tap.stanford.edu/Online demo at http://ontap.stanford.edu/sail • FOAF (Friend of a Friend) • FOAFnaut (http://www.foafnaut.org/) • FOAFCorp (http://www.grorg.org/2002/10/foafcorp/) • Photo annotation: • W3 conference photos (http://w3photo.org/ ) • Storymill (http://storymill.net/ ) • HP Semantic Web environment directory ( http://www.swed.org.uk/ ) • AKTorshttp://triplestore.aktors.org/SemanticWebChallenge/

  42. Resources – commercial applications and startups Just a selection: • Adobe XMP • Brandsoft http://www.brandsoft.com/Home • Network Inference http://www.networkinference.com/ • Semaview http://www.semaview.com/ • Immuexa (creators of Storymill) http://immuexa.com/ • Siderean http://www.siderean.com/ • Ontopia (not RDF!) http://www.ontopia.net/

  43. HP Labs semweb site http://www.hpl.hp.com/semweb/

  44. Additional Slides

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