The Semantic Web: status and prospects

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Keynote at Diffuse conference, Brussels, 2002

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The Semantic Web: status and prospects

  1. 1. The Semantic Web: Status and Prospects Guus Schreiber University of Amsterdam Co-chair W3C Web Ontology Working Group
  2. 2. 2 The Evolving Web Web of Knowledge HyperText Markup Language HyperText Transfer Protocol Resource Description Framework eXtensible Markup Language Self-Describing Documents Foundation of the Current Web Proof, Logic and Ontology Languages Shared terms/terminology Machine-Machine communication 1990 2000 2010 Berners-Lee, Hendler; Nature, 2001 DOCUMENTS DATA/PROGRAMS
  3. 3. 3 Semantics for the Web: some challenges  Machine-processable representation of semantic information  Defining semantics in an OPEN environment • Adding semantics to other people’s semantics • Ability for everyone to contribute  Ability to define mappings between semantic representations • Semantic representations are context-dependent, but commonalities can/must be captured  Creating a critical mass of semantic content • In the end, this will be the critical success factor
  4. 4. 4 W3C’s view on Web Semantics Semantic Web LayerCake (Berners-Lee, 99;Swartz-Hendler, 2001)
  5. 5. Semantic web languages provide “external” referents for XML documents CV name education work private < > < > < > < > < > < Χς > < ναµε> <εδυχατιον> <ωορκ> <πριϖατε> CV name education work private < > < > < > < > < > < Χς > < ναµε> <εδυχατιον> <ωορκ> <πριϖατε> CV name education work private < > < > < > < > < > < Χς > < ναµε> <εδυχατιον> <ωορκ> <πριϖατε> SW languages add mappings And structure.  ωορκ ϖατε εδυχ Χς ΧςΧς Χς  CV name education work private < > < > < > < > < > <  > < > < >  <⇐⇑©∨> CV name education work private < > < > < > < > < > <  > < > < >  <⇐⇑©∨> CV name education work private < > < > < > < > < > <  > < > < >  <⇐⇑©∨> CV name education work private < > < > < > < > < > <  > <  > <  >  < ⁄‹›„ > CV name education work private < > < > < > < > < > <  > < > < >  <⇐ ⇑ © ∨>
  6. 6. 6 What is an Ontology?  In philosophy: theory of what exists in the world  In IT: consensual & formal descriptionconsensual & formal description of shared concepts in a domainof shared concepts in a domain – Aid to human communication and shared understanding, by specifying meaning – Machine-processable (e.g., agents use ontologies in communication)  Ontology = key technology inOntology = key technology in semantic information processingsemantic information processing – Applications: knowledge management, e-business, industrial engineering, semantic world-wide web
  7. 7. 7 Typical semantic-web use case: image search  A person searches for photos of an “orange ape”  An image collection of animal photographs contains snapshots of orang-utans.  The search engine finds the photos, despite the fact that the words “orange” and “ape” do not appear in annotations
  8. 8. 8 Example semantic annotation
  9. 9. 9 RDF annotation about a web resource chimpanzee scratching the head young ape08.jpg active agent posture life stage Species ontology WordNet ICONCLASS
  10. 10. 10 Ontologies describes the concepts used great ape grass landsrain forest Africa chimpanzee geographical range subClassOf typical habitat
  11. 11. 11 Use of semantic markup in query interfaces
  12. 12. 12
  13. 13. 13 Annotating with a concept: term disambiguation
  14. 14. 14 W3C’s Semantic Web Activity  Started in March 2001 • Follow-up of Metadata activity  RDF Core Working Group • Revision of RDF and RDF Schema  Web Ontology Working Group • Started November 1, 2001 • 50+ members – HP, IBM, Lucent, Daimler Chrysler, Fujitsu, Intel, Sun, EDS, Motorola, Nokia, Philips, Unisys, ….  All proceedings are public • See http://www.w3.org under “Semantic Web”
  15. 15. 15 RDF and RDF Schema  RDF • Baseline representation for annotations of web resources • Simple triple format • Already many tools and used in browsers such as Mozilla  RDF Schema • Base-level specification of semantics • Language constructs include: class, property, subclass subproperty • Classes and properties are themselves also resources: enables annotations about annotations
  16. 16. 16 The Web Ontology Language OWL  OWL adds expressivity to RDF Schema to enable more powerful semantics: • cardinality restrictions, local range constraints, equality of resources, inverse, symmetric and transitive properties, boolean class combinations, disjointness and completeness  OWL Lite: subset of features that is easy to implement and use  OWL DL: subset of features supporting description-logic reasoning (e.g. useful for ontology construction)
  17. 17. 17 OWL documents Published: • Requirements document • OWL Guide (language walkthrough) • OWL Feature synopsis • OWL Reference • OWL Semantics • OWL Test cases In preparation: • UML and XML presentation syntax
  18. 18. 18 Moving to the future of the web Semantic Web LayerCake (Berners-Lee, 99;Swartz-Hendler, 2001)
  19. 19. 19 Web services require ontologies Source: the Web (can’t find it anymore)
  20. 20. 20 Use semantics for service composition Translate my symptoms from French and find me a pharmacy that has the necessary medicine (then compute how to get there and print the directions) Print the directions to a pharmacy which has a medicine that cures the symptoms that I will tell you (in French)
  21. 21. 21 Services need web logics
  22. 22. 22 Will the Semantic Web succeed?  One big plus: there is a growing need for semantic search of information  Availability of large amounts of semantic content is essential • There is a lot of content already out there.  First applications are likely to be in area of large virtual collections • E.g., cultural heritage, medicine  Web services will not work without ontologies

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