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Ontology Overview

Ontology Overview. Russ Reeves ICF International – Charleston, SC rreeves@icfi.com. Summary of Overview. Some definitions Some history Some technologies Why ontologies? Some applications The Future. Some Ontology Definitions.

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Ontology Overview

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  1. Ontology Overview • Russ Reeves • ICF International – Charleston, SC • rreeves@icfi.com

  2. Summary of Overview • Some definitions • Some history • Some technologies • Why ontologies? • Some applications • The Future

  3. Some Ontology Definitions • A branch of metaphysics concerned with the nature and relations of being. • A specification of a conceptualization of a knowledge domain. • A formal way to organize knowledge and terms expressing concepts and the relationships between them. • `Contrariwise,' continued Tweedledee, `if it was so, it might be; and if it were so, it would be; but as it isn't, it ain't. That's logic.'

  4. Mendeleev's Periodic Table - 1872

  5. Ontologies change over time

  6. The Semantic Web Technology Stack

  7. Resource Description Format (RDF) Statement = Subject + Predicate + Object = Resource + Relationship + Resource Directed Line Graph: Triples: <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> <http://www.example.org/staffid/85740> . <http://www.example.org/index.html> <http://www.example.org/terms/creation-date> "August 16, 1999" . <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/language> "en" .

  8. Another view of an RDF graph node arc node arc node

  9. RDF/XML <?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:exterms="http://www.example.org/terms/"> <rdf:Description rdf:about="http://www.example.org/index.html"> <exterms:creation-date>August 16, 1999</exterms:creation-date> </rdf:Description> <rdf:Description rdf:about="http://www.example.org/index.html"> <dc:language>en</dc:language> </rdf:Description> </rdf:RDF>

  10. RDF/S • An extensible knowledge representation language, providing basic elements for the description of ontologies. • An increase in expressiveness. • Class and subclass. • Property domain and range.

  11. The Web Ontology Language (OWL) • Three sub languages : Owl Lite, Owl DL, Owl Full. • Expressiveness increases, computability decreases. • More extensive inferencing capabilities. • ObjectProperty, DatatypeProperty, FunctionalProperty, InverseFunctionalProperty, EquivalentProperty, TransitiveProperty, SymetricProperty, Cardinality, Existential and Universal restrictions, ...

  12. Inferencing All men are mortal. Socrates is a man. Therefore Socrates is mortal.

  13. OWL deals with certainty

  14. Semantic Web Rules Language • SWRL allows you to assert more facts • SWRL exists within OWL • Temporal reasoning

  15. SWRL can help predict the future

  16. Applications • Data that needs to be distributed and integrated. • Increase efficiency of human analysts. (APEX) • Automatic software agents on the WWW. • Semantic search. • Integration of disparate RDBs.

  17. OWL Strengths • support for information integration and reuse of shared vocabularies • handling of semi-structured data • separation of syntax from data modeling • web embedding • extensibility and resilience to change • support for inference and classification, based on a formal semantics • representation flexibility, especially ability to model graph structures • ability to represent instance and class information in the same formalism and hence combine them

  18. OWL Weaknesses • weak ability to validate documents • expressivity limitations, particularly in terms of correlating across different properties of a resource • performance • XML serialization issues and impedance mismatch with XML tooling • lack of familiarity and potentially high learning curve • inability to natively represent uncertain data and continuous domains • no built-in representation of processes and change

  19. A Possible Future

  20. The capability continuum

  21. Questions ?

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