RDF

RDF, Resource Description Framework, defines the publishing of machine readable data on the web. Data published in RDF is expressed in XML using a series of statements about things. The statements are called triples and include a subject, predicate and object. The terms used to describe things are defined within ontologies.

Ontologies define vocabularies to describe things and relationships between things. Ontologies may also reflect business rules. Things are resources. Resources can be expressed as a literal or a Uniform Resource Identifier((URI)). Ontologies are usually created for a specific knowledge domain. Multiple vocabularies may be combined to publish a single data set. Vocabularies can describe the same concepts in different ways. There are methods for handling the sameness.

There is much data available in web pages today that could be extracted into RDF triples and published in XML files using RDF. For website owners interested in making data available to search engines and not wanting to perform the data extraction, existing web pages can be marked up with RDF data using attributes within current content. Rules are published in the RDFa specification. This can provide an opportunity to become familiar with existing ontologies and vocabularies while benefiting from additional search engine features.