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  • We develop ontologies to provide common understanding of information structure. If I have an ontology that contains the terminologies of different websites on fish, I can develop applications that can extract infor from all of these sites. Mian point of SemWeb: Many applications eg require geographical info. If one group of researchers develops such an onto, then others who have a need for it theijr domains can reuse it. Also, if need to builkd a large onto, can use existing ones ot take parts of differeent ones and merge them together as a starting point. Make explicit domain assumptuions: enables people to learn the terms for the domain.  FS portal, BSE symptoms query From a practical point of view, it is easier to make changes when knowledge changes. Prion causes mad cow disease. Not sure at the moment but await later confirmation. Too difficult if knowledge is hard coded into a program. Also has to do with reuseability: don’t want to customize an ontology too closely to a specific application. Have an onto on biblio metadata. I could use it in an online bookstore to help with customer shopping, or I could use it for multihost searching of digital libraries.
  • Transcript

    • 1. Tutorial 1: Ontologies Fifth AOS Workshop 27 April 2004 Friendship Hotel Beijing CHINA Anita Liang ( 梁华英 ) [email_address]
    • 2.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 3.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 4. Where does it come from? ontology n. 1692; lat. phil. onto- “being” + -logia “study of”
    • 5. Where does it come from?
      • Philosophy
        • The study of what is, what has to be true for something to exist, the kinds of things that can exist
      • AI and computer science
        • Co-opted the term. Something exists if it can be represented, described, defined (in a formal, hence, machine-interpretable way).
    • 6.
        • Where does the notion of ontology come from?
        • What exactly is an ontology?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 7. A Definition
      • “ a specification of a conceptualization…a description (like a formal specification of a program) of the concepts and relations that can exist for an agent or a community of agents.”
      • - T.R. Gruber. 1993. A translation approach to portable ontologies. Knowledge acquisition , 5(2):199-220 .
    • 8. A Definition
      • Informal
        • Terms
          • from a specific domain
          • uniquely defined, usually via natural language definitions
        • May contain additional semantics in the form of informal relations
        • machine-processing is difficult
        • Examples
          • Controlled vocabulary
          • Glossary
          • Thesaurus
    • 9. A Definition
      • Formal
        • Domain-specific vocabulary
        • Well-defined semantic structure
          • Classes/concepts/types
            • E.g., a class { Publication } represents all publications
            • E.g., a class { Publication } can have subclasses { Newspaper }, { Journal }
          • Instances/individuals/objects
            • E.g., the newspaper Le Monde is an instance of the class { Newspaper }
          • Properties/roles/slots
            • Data
              • E.g., the class { Publication } and its subclasses { Newspaper }, { Journal } have a data property { numberOfPages }
            • Object
              • E.g., the class { Publication } and its subclasses { Newspaper }, { Journal } have an object property { publishes }
        • Is machine-processable
    • 10.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 11. Why develop ontologies?
      • To share knowledge
        • E.g., using an ontology for integrating terminologies
      • To reuse domain knowledge
        • E.g., geography ontology
        • E.g., AOS
      • To make domain assumptions explicit
        • Facilitate knowledge management
          • E.g., { BSE } –causedBy-> { Prion } ????
        • Enable new users to learn about the domain
          • E.g., food safety ontology
      • To distinguish domain knowledge from operational knowledge
        • e.g., biblio metadata
    • 12.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 13. What they are good for
      • Informal
        • Controlled vocabulary
          • Beginnings of interoperability
        • Upper-level structures for extending further
          • E.g., AGRIS/CARIS categorization
        • Browsing support
          • E.g., IRS information search
        • Search
          • Limited query expansion
        • disambiguation
          • E.g., vessels
    • 14. What they are good for
      • Formal
        • Search
          • Concept-based query
            • User uses own words, language
          • Related terms
          • Intelligent query expansion: “fishing vessels in China” expands to “fishing vessels in Asia”
        • Consistency checking
          • Restrictions on properties can allow checking of validity of values
        • Interoperability support
          • Terms defined in expressive ontos allow for mapping precisely how one term relates to another
    • 15.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 16. Develop an ontology
      • Research
        • What is the domain?
        • What is the scope?
        • What will it be used for?
        • Who will be the users?
    • 17. Develop an ontology
      • Develop upper-ontology categories, e.g., concepts “process,” “state”
        • Use what is already available
          • E.g., SUMO, Cyc, WordNet
    • 18. Develop an ontology
      • Develop a domain-specific lexicon
        • Reuse one or more pieces of already existing resources
          • E.g., Agrovoc
          • Modify and extend
        • Compile large domain-specific text corpus and use tools to help identify/extract domain-specific terms
    • 19. Develop an ontology
      • Define classes and properties
        • Classes should correspond closely to nouns in the domain; properties correspond roughly to verbs.
      • Define class hierarchy
        • Top-down analysis, bottom-up analysis
        • Combination
    • 20. Develop an ontology
      • Map relations between upper and lower-level ontological items.
    • 21. Develop an ontology
      • WWW resources
        • www.taxonomywarehouse.com
        • www.dmoz.com
        • protégé.stanford.edu/ontologies/ontologies.html
        • directory.google.com/top/reference/knowledge_management/knowledge_representation/ontologies
        • www.nlm.nih.gov/research/umls
        • www.cyc.com
        • www.slais.ubc.ca/resources/indexing/database1.htm#online
    • 22. Develop an ontology
      • Choose an appropriate ontology language.
        • RDF
        • RDFS
        • OWL
    • 23. Develop an ontology
      • Develop evaluation method.
        • Test for consistency, completeness through application development and debugging.
        • Use subject matter experts to evaluate.
    • 24.
        • Where does the notion of ontology come from?
        • What exactly is an ontology, anyway?
        • Why develop an ontology?
        • What can an ontology be used for ?
        • How can I develop one?
        • Which language should I choose?
      What this talk is about
    • 25. Resource Description Framework
      • RDF is
        • a formalism for representing metadata
        • a way to describe the semantics of information
    • 26. Resource Description Framework
      • RDF data model
        • Resource
          • The basic unit being described, includes any object such as website, document, picture, etc.
          • Identified via URI
        • Property
          • Characteristic of a resource
          • Also identified via URI
        • Statement
          • Describes properties of resources
          • Triples: <Subject, Predicate, Object>
      • URI
        • Uniform Resource Identifier
        • Used for uniquely identifying resources
    • 27. Resource Description Framework
      • Syntax
        • Based on xml
        • <Description> element describes a resource
        • Attribute or nested element describes a property
          • <rdf:Property rdf:ID=“afflicts”></ rdf:Property >
          • <rdf:Description rdf:about=“http//:www.fao.org/aos/bse”>
            • < afflicts resource=“http//:www.fao.org/aos/cow”>
            • </ afflicts>
          • </rdf:Description>
    • 28. Resource Description Framework
      • No systematic semantics, esp. in terms of hierarchy
    • 29. Resource Description Framework Schema
      • Allows for interpretation of resources
      • Some RDFS terms:
        • Class
          • Defines categories into which resources can be grouped
        • subClassOf
          • Allows the creation of hierarchy of classes
        • Domain, range
          • Constrains the classes that can be subject and object of property, respectively
        • subPropertyOf
          • Properties can be inherited
    • 30. Resource Description Framework Schema
      • Inferencing is possible
        • Assertions:
        • { Dolly } instanceOf { BlueSheep }
        • { BlueSheep } hasMother { BlueSheep }
        • { Dolly } hasMother { Kristine }
        • Inference:
        • { Kristine } instanceOf { BlueSheep }
    • 31. Resource Description Framework Schema
      • But still not expressive enough
        • No domain/range constraint at the local level
        • No cardinality constraints
        • No transitive, symmetrical, inverse properties
    • 32. Web Ontology Language (OWL)
      • OWL consists of all elements and attributes provided by RDF and RDFS, but goes beyond, allows greater inferencing capabilities.
        • allows info to be gathered from distributed sources
        • instance document can be enhanced with an OWL property to indicate that it’s the same as another instance. For example,
          • Police report shows that Sam is suspected of being a drug king.
            • Sam suspectedOf drug king
          • FBI file shows that Tony is a mafia boss
            • Tony suspectedOf mafia
          • CIA has a file on Tony.
            • Tony owl:sameIndividualAs Sam
          • Inference: the drug king is the same as the mafia boss,
    • 33. Web Ontology Language (OWL)
      • OWL consists of all elements and attributes provided by RDF and RDFS, but goes beyond, allows greater inferencing capabilities.
        • provides capability of constructing taxonomies which can be used to dynamically understand how an instance relate to other entities
          • 1. User: Is Virago a motorcycle?
          • 2. Web agent goes to websites: Send me your catalog.
          • 3. Catalog contains:
            • <custom rdf:ID=“Virago”>
              • <size>535 cc</size>
              • <cylinder>2</cylinder>
            • </custom>
          • 4. Web agent consults ontology:
            • { Sport } subClassOf { Motorcycle }
            • { Custom } subClassOf { Motorcycle }
            • { Grand Tourism } subClassOf { Motorcycle }
          • 5. Inference: The Virago is a custom motorcycle.
    • 34. Web Ontology Language (OWL)
      • OWL consists of all elements and attributes provided by RDF and RDFS, but goes beyond, allows greater inferencing capabilities.
        • provides capability of specifying that a property can relate a resource to a specific number of other resources;
          • 1. User: What is Jill’s birthplace?
          • 2. { Person } –hasBirthplace-> 1 { Location }
          • 2. Three different documents found:
            • Document A: { Jill } hasBirthplace { Texas }
            • Document B: { Jill } hasBirthplace { Lone Star State }
            • Document C: { Jill } hasBirthplace { Middle of Nowhere }
          • 3. Inference: Texas, Lone Star State, and Middle of Nowhere all refer to the same location.
    • 35. Web Ontology Language (OWL)
      • Owl Lite
        • Classification hierarchy, simple constraints, e.g., cardinality is 1 or 0
      • Owl DL
        • Maximum expressivity and also computationally complete
      • OWL Full
        • Maximum expressivity but no computational guarantees
    • 36.
      • Questions?
      • References:
        • www.w3.org
        • Ontology resources
      • Thank you for coming.

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