(2013-06-03) Ghislain Atemezing: It is important to understand the relationship beween VoID and DCAT: In short, VoID is for data in RDF format, while DCAT is neutral with regards to format. (See the introduction section of DCAT vocabulary: http://www.w3.org/TR/vocab-dcat/)
(2015-05-04) Bernard Vatant: VoID is specified by a W3C Interest Group Note at http://www.w3.org/TR/void/, which is stable, including the namespace http://rdfs.org/ns/void#. This namespace used to redirect to http://vocab.deri.ie/void, which is declaring itself as the vocabulary URI in the RDF file. Unfortunately both URI and namespace are offline at the moment, future of vocab.deri.ie being unknown.