Download Static program analysis and its application to TI`s DSP Processor

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.:
• 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 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 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 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 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
http://www.example.org/index.html has a creator whose value is John Smith
Resource Description Framework
http://www.example.org/index.html has a creation-date whose value is August 16, 1999
http://www.example.org/index.html has a language whose value is English
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
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 Framework
• With the namespace, the triples written as:
ex:index.html dc:creator exstaff:85740
ex:index.html exterms:creation-date “8/16/99”
ex:index.html dc:language "en"
• RDF only recognizes full URIs
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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
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For RDF to be useful resources should use
common terminology (ontology)
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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 Ontologies
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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
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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>