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Resource Description Framework (RDF)

Learn about RDF, ontology, RDF data model, history, syntax, and how RDF enables metadata exchange through this comprehensive guide.

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Resource Description Framework (RDF)

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  1. Resource Description Framework (RDF) Presented by: Jonathan Catlett

  2. Presentation Topics • Background • Overview • Example • What is RDF? • History • Syntax • Conclusion

  3. Background • Metadata • Structured data about data • Used by clients (web browsers) to improve discovery and access of distributed information. • Usually imbedded into HTML to tell the browser what information is contained in the page.

  4. Background • Ontology • Describes the structure of information at different levels of abstraction. • A tree-like structure which can be used to describe semantics. • Parse trees • For this presentation we will use an ontology only to describe the hierarchy of the resources or information.

  5. Ontology

  6. Overview • The Resource Description Framework is an infrastructure that enables the exchange of metadata structured in an ontology. • Let us show this using an example!

  7. Example! • Lets say there is a document server and a client that would like a list of the documents. • Very simple example. • We will see sample syntax later.

  8. Another Example! • What about a server that maintains bookmarks instead of documents? • Pretty simple! • Now what if one of the bookmarks is a link to a script that will list all of the client’s current email on the server? • Then the structure gets more complex and dynamic. • This is where the RDF’s ability to handle the ontology is needed.

  9. What is RDF? • Developed by the World Wide Web Consortium (W3C) to provide a standard for defining an architecture for supporting the vast amount of web metadata. • Implemented using XML! • Since it is an application of XML, it inherits the syntax from XML. • Namespaces for example.

  10. What is RDF? • Human and machine readable • Machine-readable just means that it maintains the structure of the ontology. • This is very important.

  11. What is RDF? • For example, the following two sentences mean the same thing to a human, but are very different to a machine. • “The author of Document 1 is John Smith” • “John Smith is the author of Document 1” • RDF maintains the semantics and is unambiguous.

  12. What is the RDF Data Model? • This is how the data is represented using XML. • A Resource is any object identifiable by a URI. • The properties associated with a resource are property-types. • Each property-type has a value. • A collection of property-types for the same resource is called a Description.

  13. RDF Data Model Diagram

  14. What is the RDF Data Model? • These Descriptions are kept unambiguous using the XML syntax and namespaces. • Property-types may also contain collections of values • Bags – Simple collection • Sequence – Order matters • Alternative – If-then type structure.

  15. History • How did this all come about you may ask. • Metadata began in 1995 with PICS. • Platform for Internet Content Selection (PICS) • Mechanism for communicating ratings of web pages from server to clients. • Content control • Introduced a general mechanism for creating rating system. • No fixed set of criteria.

  16. History • W3C started thinking about the general problem of Interned resource description based on the PICS architecture. • W3C formed the PICS-NG (Next Generation) working group. • This eventually led to the development of the Resource Description Framework (RDF)

  17. Syntax • Simple document report <? xml version="1.0" ?> <RDF xmlns = "http://w3.org/TR/1999/PR-rdf-syntax-19990105#" xmlns:DC = "http://purl.org/DC#" >  <Description about = "http://dstc.com.au/report.html" > <DC:Title> The Future of Metadata </DC:Title> <DC:Creator> Jacky Crystal </DC:Creator> <DC:Date> 1998-01-01 </DC:Date> <DC:Subject> Metadata, RDF, Dublin Core </DC:Subject> </Description> </RDF>

  18. Syntax • Complex Value ... <DC:Creator parseType="Resource"> <vCard:FN> Dr Jacky J Crystal </vCard:FN> <vCard:TITLE> Director </vCard:TITLE> <vCard:EMAIL> jacky@dstc.com.au </vCard:EMAIL> <vCard:ROLE> Researcher </vCard:ROLE> </DC:Creator> ...

  19. Syntax • Bag ... <DC:Creator> <Bag> <li> Maddie Azzurii </li> <li> Corky Brown </li> <li> Jacky Crystal </li> </Bag> </DC:Creator> ...

  20. Syntax • Sequence ... <DC:Creator> <Seq> <li> Maddie Azzurii </li> <li> Corky Brown </li> <li> Jacky Crystal </li> </Seq> </DC:Creator> ...

  21. Syntax • Alternative ... <vCard:ROLE> <Alt> <li xml:lang="en"> Programmer </li> <li xml:lang="fr"> Programmeur </li> <li xml:lang="it"> Programmatore </li> </Alt> </vCard:ROLE> ...

  22. Syntax • RDF Schema <? xml version="1.0" ?> <RDF xmlns = "http://w3.org/TR/PR-rdf-syntax#" xmlns:RDFS = "http://w3.org/TR/WD-rdf-schema#" >  <Description ID = "Title" > <type resource = "http://w3.org/TR/PR-rdf-syntax#Property" /> <RDFS:label> Title </RDFS:label> <RDFS:comment> The name given to the resource, usually by the Creator or Publisher </RDFS:comment> </Description>  <Description ID = "Creator" > <type resource = "http://w3.org/TR/PR-rdf-syntax#Property" /> <RDFS:label> Author or Creator </RDFS:label> <RDFS:comment> The person or organisation primarily responsible for the intellectual content of the resource </RDFS:comment> </Description>  </RDF>

  23. Conclusion • RDF provides a needed standard for describing resources between client and server. • The next step is to get organizations to use the RDF instead of proprietary resource descriptions. • The increasing popularity of XML and JAVA should help the acceptance of RDF.

  24. Resources • An Introduction to the Resource Description Framework • www.dlib.org/dlib/may98/miller/05miller.html • An Idiot’s Guide to the Resource Description Framework • www.dstc.edu.au/Research/Projects/rdf/RDF-Idiot.html • RDF: In Fifty Words or Less • www.mozilla.org/rdf/50-words.html

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