An announcement from the W3C, July 17, 2008 (thanks to Pete Johnston):
We’re glad to announce Vapour 2.0, a validator for Linked Data and RDF vocabularies. An effort has been made to widen the scope of the validation to cover any kind of Linked Data (Vapour 1.0 was specifically targeted to RDF vocabularies). This new release contains a number of new exciting features, such as checking for meaningful triples in the response documents, links to popular semantic web browsers, and conclusions on the type of the resources per httpRange-14. Moreover, the input form is now simpler, and the reports are even more eye-catching than before.
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PS: For background, see Tim Berners-Lee’s description of Linked Data (July 2006).