Introduction to RDF

The Resource Description Framework (RDF) is a W3C standard for describing Web resources, such as the title, author, modification date, content, and copyright information of a Web page.

What is RDF?

• RDF stands for Resource Description Framework
• RDF is a framework for describing resources on the web
• RDF provides a model for data, and a syntax so that independent parties can exchange and use it
• RDF is designed to be read and understood by computers
• RDF is not designed for being displayed to people
• RDF is written in XML
• RDF is a part of the W3C's Semantic Web Activity
• RDF is a W3C Recommendation

RDF - Examples of Use

• Describing information about web pages, such as content, author, created and modified date
• Describing content and rating for web pictures
• Describing content for search engines
• Describing electronic libraries

RDF is Designed to be Read by Computers

RDF was designed to provide a common way to describe information so it can be read and understood by computer applications.

RDF descriptions are not designed to be displayed on the web.

RDF is Written in XML

RDF documents are written in XML. The XML language used by RDF is called RDF/XML.

By using XML, RDF information can easily be exchanged between different types of computers using different types of operating systems and application languages.

RDF and "The Semantic Web"

The RDF language is a part of the W3C's Semantic Web Activity. W3C's "Semantic Web Vision" is a future where:

• Web information has exact meaning
• Web information can be understood and processed by computers
• Computers can integrate information from the web

RDF is a W3C Recommandation

RDF became a W3C Recommendation in February 2004.

A W3C Recommendation is understood by the industry and the web community as a web standard. A W3C Recommendation is a stable specification developed by a W3C Working Group and reviewed by the W3C Membership.

The official W3C recommendation can be found at this link:

http://www.w3.org/RDF/

 RDF Rules

RDF uses Web identifiers (URIs) to identify resources.

RDF describes resources with properties and property values.

RDF Resource, Property, and Property Value

RDF identifies things using Web identifiers (URIs), and describes resources with properties and property values.

Explanation of Resource, Property, and Property value:

• A Resource is anything that can have a URI, such as "http://www.w3schools.com/RDF"
• A Property is a Resource that has a name, such as "author" or "homepage"
• A Property value is the value of a Property, such as "Jan Egil Refsnes" or "http://www.w3schools.com" (note that a property value can be another resource)

The following RDF document could describe the resource "http://www.w3schools.com/RDF":

<?xml version="1.0"?>

<RDF>
  <Description about="http://www.w3schools.com/RDF">
    <author>Jan Egil Refsnes</author>
    <homepage>http://www.w3schools.com</homepage>

  </Description>
</RDF>

The example above is simplified. Namespaces are omitted.

RDF Statements

The combination of a Resource, a Property, and a Property value forms a Statement (known as the subject, predicate and object of a Statement).

Let's look at some example statements to get a better understanding:

Statement: "The author of http://www.w3schools.com/RDF is Jan Egil Refsnes".

• The subject of the statement above is: http://www.w3schools.com/RDF
• The predicate is: author
• The object is: Jan Egil Refsnes

Statement: "The homepage of http://www.w3schools.com/RDF is http://www.w3schools.com".

• The subject of the statement above is: http://www.w3schools.com/RDF
• The predicate is: homepage
• The object is: http://www.w3schools.com