Resource description framework
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Resource Description Framework. Gopal Gupta Department of Computer Science University of Texas at Dallas. Resource Description Framework. RDF is a language for Representing resources on the world wide web Representing meta-data about web resources; E.g.:

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Resource Description Framework

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Resource description framework

Resource Description Framework

Gopal Gupta

Department of Computer Science

University of Texas at Dallas


Resource description framework1

Resource Description Framework

  • RDF is a language for

    • Representing resources on the world wide web

    • Representing meta-data about web resources; E.g.:

      • title/author/etc of a webpage (a resource)

      • availability schedule of a resource

  • RDF can represent information about things that can be identified on the web, even though they cannot be retrieved:

    • person, physical book, building


Resource description framework2

Resource Description Framework

  • RDF meant for automatic processing (not just for humans)

  • RDF provides a common framework that:

    • Eases communication

    • Allows leveraging of common tools

    • Allows information to be used by applications other than the original one for which the RDF document was created.

      (Hence the notion of a resource important)


Resource description framework3

Resource Description Framework

  • RDF is based on the idea of:

    • identifying things using web identifiers (URIs)

    • describing resources via properties and property values

  • The thing identified, its property, as well its property values can all be URIs

  • Uniform Resource Identifiers: More general than URLs;

  • URIs Can identify:

    • Network accessible things (documents and databases)

    • Any physical object (book, human)

    • Abstract concepts (creator)


Resource description framework4

Resource Description Framework

  • RDF uses URI references (or URIref):

    • a URI, together with an optional fragment identifier.

    • E.g.: http://www.example.org/index.html#section2

    • Don’t have to write full URIs; abbreviate via name-spaces

  • All information in RDF coded in the form:

    • X has a property P whose value is Y

      - X is the subject

      - P is the property

      - Y is the object

    • All of X, P, and Y can be URIs or literal atoms


Resource description framework5

Resource Description Framework

  • Two issues to allow machine processable KR

    • Need to uniquely identify subject, prop, object

      -- use URIs

    • Need to put in machine processable format

      -- use XML (RDF Schema)

    • RDF represents information as graphs:

      -- subject & object become nodes

      -- property becomes the arc

      -- URIrefs put in ellipses; literals (typed) in boxes


Resource description format

Resource Description Format

http://www.example.org/index.html has a creator whose value is John Smith


Resource description framework6

Resource Description Framework

http://www.example.org/index.html has a creation-date whose value is August 16, 1999http://www.example.org/index.html has a language whose value is English


Rdf triples

RDF 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" ]


Namespaces in rdf

Namespaces in RDF

prefix rdf:, namespace URI: http://www.w3.org/1999/02/22-rdf-syntax-ns#prefix rdfs:, namespace URI: http://www.w3.org/2000/01/rdf-schema#prefix dc:, namespace URI: http://purl.org/dc/elements/1.1/prefix owl:, namespace URI: http://www.w3.org/2002/07/owl#prefix ex:, namespace URI: http://www.example.org/ prefix xsd:, namespace URI: http://www.w3.org/2001/XMLSchema#

Other namespaces:prefix exterms:, namespace URI: http://www.example.org/terms/

-- (for terms used by an example organization),prefix exstaff:, namespace URI: http://www.example.org/staffid/

-- (for the example organization's staff identifiers),prefix ex2:, namespace URI: http://www.domain2.example.org/

-- (for a second example organization), and so on.


Resource description framework7

Resource Description Framework

  • With the namespace, the triples written as: ex:index.html dc:creator exstaff:85740ex:index.html exterms:creation-date “8/16/99”

    ex:index.html dc:language "en"

  • RDF only recognizes full URIs

    • Namespace/qualified names just conveniences

    • Namespace structure should not be utilized

    • URIs define standard vocabularies (ontologies)

    • Same resource may have multiple URIs


Rdf and ontologies

RDF and Ontologies

  • For RDF to be useful resources should use common terminology (ontology)

    • Someone could search the web for book reviews and create an avg rating for each book, then post it as a resource.

    • This resource could be used to create another resource, namely, “top 10 books”

  • Possible only if people using this resource can agree on a common terminology (or ontology); thus common ontologies need to be developed


Rdf and ontologies1

RDF and Ontologies

  • RDF defines its own tags (RDF schemas)

  • RDF does not give meaning to tags, these are defined in other name spaces (e.g., creator)

  • The meaning of these tags are interpreted by applications

  • RDF provides means for knowledge representation, much like a logical formalism, e.g., assertions in formal logic,


Rdf in xml syntax

RDF in XML Syntax

  • 1. <?xml version="1.0"?>

  • 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

  • 3. xmlns:exterms="http://www.example.org/terms/">

  • 4. <rdf:Description rdf:about="http://www.example.org/index.html">

  • 5. <exterms:creation-date>August 16,1999</exterms:creation-date>

  • 6. </rdf:Description>

  • 7. </rdf:RDF>


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