Introduction to RDF 1

Introduction to RDF

Ken Varnum

9 October 2007

Introduction to RDF 2

Definition of RDF

The Resource Description Framework (RDF) is a general-purpose language for representing information in the Web.

RDF Vocabulary Description Language 1.0: RDF Schema

Significant Part of “Semantic Web”

XML-based tool for describing resources

Introduction to RDF 3

What’s It Good For?

“…[D]oes not specify a vocabulary of descriptive properties such as "author". Instead it specifies mechanisms that may be used to name and describe properties and the classes of resource they describe.”

Used to describe• Source of ontology• What is being described• Description

Not an Ontology

Introduction to RDF 4

Concept of “Triples”

Subject - Predicate - Object• Something• Has the Property• Characteristic

Properties are defined -- in human- or machine-readable format -- at a given URI.

Introduction to RDF 5

Example

Michigan has the postal abbreviation MI

Subject Predicate Object

Michigan has the postal abbreviation

MI

Introduction to RDF 6

Convert to RDF -- Step 1

First do the XML thing -- declare name spaces<rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#

xmlns:terms="http://purl.org/dc/terms/">

</rdf:RDF>

Two name spaces• rdf (defined by W3C)• terms (defined by Dublin Core)

Introduction to RDF 7

Convert to RDF -- Step 2

Add Subject<rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#

xmlns:terms="http://purl.org/dc/terms/">

<rdf:Description rdf:about="urn:x-states:Michigan">

</rdf:Description>

</rdf:RDF>

• Use “Description” from the RDF namespace• Definition found at RDF “x-states” site

Introduction to RDF 8

Convert to RDF -- Step 3

Add Object<rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#

xmlns:terms="http://purl.org/dc/terms/"> <rdf:Description rdf:about="urn:x-states:Michigan"> <terms:alternative>MI</terms:alternative> </rdf:Description></rdf:RDF>

• Use “alternative” from the terms namespace• Definition found at Dublin Core site• DC only defines purpose of “alternative” in a

machine-readable way

Introduction to RDF 9

Where Is It?

A “flavor” of RSS• RDF• RSS• Atom

Underlies data exchange

As a rule, systems generate it, not people

Introduction to RDF 10

Foundation of “Semantic Web”

“What is meant by ‘semantic’ in Semantic Web is not that computers are going to understand the meaning of anything, but that the logical pieces of meaning can be mechanically manipulated by a machine to useful human ends.”

“What Is RDF” by Joshua Tauberer

Introduction to RDF 11

Sources / Further Reading

Wikipedia entry on RDF (overview)http://en.wikipedia.org/wiki/Resource_Description_Framework

RDF Specification (technical)http://www.w3.org/RDF/

What Is RDF (overview)http://www.xml.com/lpt/a/1665