1. An evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a format which can be read and used by software agents; therefore, permitting them to find, share and integrate information more easily.

It derives from W3C director Tim Berners-Lee's vision of the Web as a universal medium for data, information, and knowledge exchange.

2. A set of formats and languages that find and analyze data on the World Wide Web, allowing consumers and businesses to understand all kinds of useful online information.