Semantic Web is global mesh of information that is easily processed by machines. It is an efficient way to represent data on the World Wide Web. This sytem was thought up by Tim Bernes-Lee, who was the inventor of the WWW, URIs, HTTP, and HTML. It is constantly worked on by a team of people at the World Wide Web consortium (W3C). Also many languages, publications and tools have already been developed based on this sytem.
The Semantic Web allows people to publish and find information faster and easier. It is built on syntaxes which us URIs, Uniform Resource Identifier, to represent data, usually in triples based structures. A language which uses URIs is called RDF, Resource Description Framework. RDF XML is considered to be the standard interchange format for RDF on the Semantic Web. Semantic Web languages are very powerful in that they make it very easy for people to create and publish information using URIs and that it is very unconstraining in what it lets people say and do. But at the same time, they are the basis for very well defined and structured applications.
The next step in the architecture of the Semantic Web is trust and proof. Applications on the Semantic Web will depend on context generally to let people know whether or not to trust the data. These applications will generally contain proof checking mechanisms and digital signatures. The Semantic Web is growing and it is important that we address these issues before they get out of control.
Source: The Semantic Web: An Introduction [http://infomesh.net/2001/swintro/]