Ontologies - Multi Agent Systems - Lecture Slides, Slides of Multiagent Systems

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Ontologies

Ontologies

• Ontologies are explicit formal specifications of the terms in the domain and relations among them (Gruber 1993).
• Why would someone want to develop an ontology? Some of the reasons are: - To share common understanding of the structure of information among people or software agents - To enable reuse of domain knowledge - To make domain assumptions explicit - To separate domain knowledge from the operational knowledge - To analyze domain knowledge

Ontology systems

• Languages
  • CLIPS, Jess
  • XML
  • RDF
  • DAML+OIL
  • CycL
• Ontology editors
  • Protégé-
• Standardized ontologies
  • Dublin Core Ontology
  • Cyc Upper Ontology
  • … etc.

Resource Description Framework

RDF (cont’d)

• The Resource Description Framework (RDF) is a language for representing information about resources in the World Wide Web.
• It is particularly intended for representing metadata about Web resources, such as the title, author, and modification date of a Web page, copyright and licensing information about a Web document, or the availability schedule for some shared resource.
• However, by generalizing the concept of a "Web resource", RDF can also be used to represent information about things that can be identified on the Web, even when they can't be directly retrieved on the Web. RDF provides a common framework for expressing this information so it can be exchanged between applications without loss of meaning.

RDF (example)

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://www.w3.org/2000/10/swap/pim/contact#"> Eric Miller Semantic Web Activity Lead

</rdf:RDF>

RDF: Uniform Resource Identifiers

• URIs are not limited to identifying things that have network locations, or use other computer access mechanisms. In fact, we can create a URI to refer to anything we want to talk about, including
• network-accessible things, such as an electronic document, an image, a service (e.g., "today's weather report for Los Angeles"), or a collection of other resources.
• (^) things that are not network-accessible, suchDocsity.com

URI: examples:

• http: (Hypertext Transfer Protocol, primarily for Web pages)
• mailto: (email addresses), e.g., mailto:[email protected]
• ftp: (File Transfer Protocol)
• urn: (Uniform Resource Names, intended to be persistent location-independent resource identifiers), e.g., urn:isbn:0-520-02356-0 (for a book)

RDF Reification

• RDF applications sometimes need to make statements about statements , for instance, to record information about when a statement was made, who made it, or other similar information
• That is, we want to be able to turn the original statement into a resource, so that we can make it the subject of another RDF statement that talks about it. RDF provides a built-in vocabulary for modeling statements as Docsity.com