From TBL's page on Linked Data (the springboard):
The Semantic Web isn't just about putting data on the web. It is about making links, so that a person or machine can explore the web of data. With linked data, when you have some of it, you can find other, related, data.
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- Use URIs as names for things
- Use HTTP URIs so that people can look up those names.
- When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL)
- Include links to other URIs. so that they can discover more things.
From the RDF Primer (visit the EM ex.):
The Resource Description Framework (RDF) is a language for representing information about resources in the World Wide Web.
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Unlike triples, which are intended as a shorthand notation, RDF/XML is the normative syntax for writing RDF.
See the known world of linked data in the graph at linkeddata.org. Resources of note are AudioScrobbler, DBpedia, Freebase, and US Census Data (working SPARQL endpoint).
And in libraries: id.loc.gov and LIBRIS.
LOD is rough around the edges, full of broken links and draft papers. Nonetheless, it's a beginning.