What is RDF and what is it good for? | | |
This is an introduction to RDF (“Resource Description Framework”), which is the standard for encoding metadata and other knowledge on the Semantic Web. In the Semantic Web, computer applications make use of structured information spread in a distributed and decentralized way throughout the current web. RDF is an abstract model, a way to break down knowledge into discrete pieces, and while it is most popularly known for its RDF/XML syntax, RDF can be stored in a variety of formats. This article discusses the abstract RDF model, two concrete serialization formats, how RDF is used and how it differs from plain XML, higher-level RDF semantics, best practices for deployment, and querying RDF data sources. | | |
This document was originally written in October 2005. In July 2006 it was revised and extended with material from my xml.com article "What is RDF". In January 2008 it was revised with more on N3 and RDF/XML and extended with the new sections Linked Data for the Web and Querying Semantic Web Databases | | |
Why we need a new standard for the Semantic Web | | |
On the Semantic Web, computers do the browsing for us. The “SemWeb” enables computers to seek out knowledge distributed throughout the Web, mesh it, and then take action based on it. To use an analogy, the current Web is a decentralized platform for distributed presentations while the SemWeb is a decentralized platform for distributed knowledge. RDF is the W3C standard for encoding knowledge. | | |
There of course is knowledge on the current Web, but it's off limits to computers. Consider a Wikipedia page, which might convey a lot of information to the human reader, but to the computer displaying the page all it sees is presentation markup. To the extent that computers make sense of HTML, images, Flash, etc., it's almost always for the purpose of creating a presentation for the end-user. The real content, the knowledge the files are conveying to the human, is opaque to the computer. | | |
What is meant by “semantic” in the 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 ends. | | |
