Transcript Ontologies and the Semantic Web

Ontologies
and
the Semantic Web
by
Ian Horrocks
presented by
Thomas Packer
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Overview
• The current web is simple and usable.
• More could be done to build more intelligent tools (agents).
• Doing this requires solving hard problems:
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Knowledge representation and reasoning
Natural language processing
Computer vision
Agent systems
• “My aim here is to show here that even if a full realization
of the Semantic Web is still a long way off, Semantic Web
technologies already have an important influence on the
development of information technology.”
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Challenges
• Natural language:
– Page says “Harry Potter has a pet named Hedwig.”
– Search for pages about wizards owning raptors.
– Solution: interpret and represent in machine
readable format.
• Distributed information:
– Ask a question whose answer is not found on one
page.
– Solution: Integrate facts in integratable formats.
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Set of RDF Triples = RDF Graph
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Challenge Solved
• Page says “Harry Potter has a pet named
Hedwig.”
• Search for pages about wizards owning
raptors.
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OWL and Class Definitions
• Extensional Definition
• Intensional Definition
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Use of Description Logic
in OWL Ontologies
• Infer new facts
– Unlike databases with a closed-world assumption
(e.g. unasserted information is assumed false)
• Temporary inconsistency allowed
– Unlike database that prevent assertions that
violate constraints (e.g. unique names)
• Warnings in a ontology development
environment to guide debugging.
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Conclusion
• OWL and RDF are good tools, particularly in
applications where
– Information has high value
– The schema plays an important role
– Information may be incomplete
• They are working on making it more expressive (OWL 2
and SWRL), scalable and modular.
• Will be more useful as more people use them and
provide tools for working with them.
• Our research could make use of existing knowledge,
plus reasoning, to do better information extraction
from web pages.
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Questions
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