RDF
RDF—the Resource Description Framework—is a standard model for data interchange on the Web. RDF has features that facilitate data merging even if the underlying schemas differ, and it specifically supports the evolution of schemas over time without requiring all the data consumers to be changed.
RDF extends the linking structure of the Web to use URIs to name the relationship between things as well as the two ends of the link (this is usually referred to as a “triple”). Using this simple model, it allows structured and semi-structured data to be mixed, exposed, and shared across different applications.
This linking structure forms a directed, labelled graph, where the edges represent the named link between two resources, represented by the graph nodes. This graph view is the easiest possible mental model for RDF and is often used in easy-to-understand visual explanations.
Recommended Reading
The RDF Specification consists of a suite of W3C Recommendations, published in 2004. A number of Notes have also been published although, by now, many of them are of a historical interest only.
See also Tim Berners-Lee's writings on Web Design Issues, including Metadata Architecture. Other technologies, like OWL or SKOS, build on RDF and provide language for defining structured, Web-based ontologies which enable richer integration and interoperability of data among descriptive communities.
A number of textbooks have been published on RDF and on Semantic Web in general. Please, refer to a separate page listing some of those, as maintained by the community. That list also includes references to conference proceedings and article collections that might be of general interest.
Tools
The last few years have seen a large number of tools, development environments that make RDF based application development possible. The community maintains a separate Wiki page listing those.
Tools
Relevant tools and application environments, described elsewhere on this wiki, are in the table below. (See also in CSV and RSS formats.)