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Semantic Web

Semantic Web. Definition. The Semantic Web is a vision: the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications.---- W3C.org. Technologies.

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Semantic Web

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  1. Semantic Web

  2. Definition • The Semantic Web is a vision: the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications.---- W3C.org

  3. Technologies • XML- Extensible Markup Language • RDF- Resource Description Framework • RDFS- Resource Description Framework Schema • OWL- Web Ontology Language • Knowledge Representation

  4. Semantic Web Model

  5. XML • Extensible Markup Language (XML) is a simple, very flexible text format derived from SGML (ISO 8879). Originally designed to meet the challenges of large-scale electronic publishing, XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere. ----W3C.org

  6. Resource Definition Framework (RDF) • RDF is effectively the application of formal logic to the study of resources, which are represented in RDF by URIs (such as URLs) or literals. It provides a means to express and process simple assertions, such as “an apple is a fruit”. • RDF statement “an apple is a fruit” has three parts: a subject (an apple), a predicate (“is a type of”) an object (“fruit”). • The subject and the predicate must be uniform resource identifier (URI) while the object can be a URI or literal.

  7. RDF Model http://www.kasm.nii.ac.ip/takeda Creator “Hideaka Takeda’’’ Resource Property Value

  8. XML and RDF Markup Code

  9. Explanation of Code • Line 01 XML version • Line 02 shows the following line until the </rdf:RDF> are RDF statements. • Line 03 and 04 are name spaces that define RDF. • Line 05-07 are actual description of the RDF statement. • The <rdf:description> start with attribute about is used to specify a resource. • The <dc:creator> start tag specifies a property and the value of the property is between start and end tag.

  10. RDF Model Creator http://www.kasm.nii.ac.jp/~takeda name email “Hideaki Takeda” “ takeda@nii.ac.jp “

  11. RDF Code for Previous Example

  12. Software • RDF University of Bristol’s – Redmond HP’s ---- Jena

  13. Resource Definition Framework Schema (RDFS) • Provides additional modeling primitives on top of RDF, i.e. a simple model of classes and their relations can be defined with RDFS. • We can use RDFS to define a structure of classes then it acts as a vocabulary of RDF statements in turn.

  14. RDFS Schema Code

  15. Web Ontology Language (OWL) • Adds more vocabulary for describing properties and classes: relations between classes, cardinality, equality, richer typing of properties, characteristics of properties, and enumerated classes.

  16. OWL Markup Language

  17. Owl Tutorial W3C site http://www.w3.org/TR/owl-guide/

  18. Software • OWL IBM’s SNOBASE- (Semantic Network Ontology Base) Stanford University’s- Protégé Network Inference’s- Construct

  19. Combining Different Ontology’s • As companies and individuals construct separate ontologies there will be a need to combine or map of relations between two ontologies. • Ontology mapping is defined as the process whereby semantic relations are defined at ontological level between source and target entities, and are further applied at instance level transforming source ontology instances into target ontology instances.

  20. Phases of Mapping or Semantic Bridging • Phase I – Specification • Occurs at meta-level. • Defined as function between source and target ontology elements. M : Os Ot M is ontology mapping document, or simply ontology mapping

  21. Phase II Execution • Function between source knowledge base and target knowledge base • T(M) : KBs KBt

  22. MARFA Toolkit-Semantic Bridge • Is used to combine ontologies using set and graph math to define elements, relations and properties. • It then is used to combine the knowledge bases instances.

  23. MARFA Concept Bridge • Only allows cardinality of 1:1- thus many concept bridges must be defined to capture all concepts.

  24. Property Bridge • Transforms property instances. Cardinality can be 0:1, 1:1, 1:n, m:1, m:n.

  25. Paths • Allow querying of knowledge base, whose result is a particular view over the knowledge base.

  26. Condition Expression • Attached to each semantic bridge in order to constrain their execution. • Condition expressions are boolean expressions over mathematical expressions.

  27. Semantic Bridges Inter-relations • Are defined in the context of the ontology mapping document.

  28. MARFA System Architecture

  29. MARFA • Has had positive results on mapping Gedcom ontology and Gentology ontology had faster result than OntoMerge with no significant difference in results.

  30. Questions?

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