DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web. DBpedia allows you to ask sophisticated queries against Wikipedia, and to link other data sets on the Web to Wikipedia data.
Nova Spivack's semantic web company Twine is developing a free service to write and host semantic ontologies; the classification trees that enable machines to put concepts in topical context.
The Semantic Web provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF).
This lecture elaborates on RDF, RDFS, and SOAP starting from a short recap of XML, and the history of the W3C and the development of "open standard recommendations". We also compare RDF triples with DOGMA lexons. We finalise by listing shortcomings of RDFS regarding semantics, and give short overview of the history of OWL as one answer to this. A full elaboration on OWL and description logic is for another lecture.
In practice, it is assumed that most URNs will refer to on-line resources, and that a mechanism will exist which takes a URN and returns a list of URLs[20]. Another, intriguing, possibility is that URNs may be linked to other URNs rather than directly to URLs. This raises the prospect of their being used to establish a semantic network of pointers to resources - a true virtual library!