Best open-source ontology/vocabulary visualization tool?

Quick question - what is the best open-source best (or a web service)
to visualize, preferably as a tree, an existing RDF(S) vocabulary or
OWL ontology?

There seems to be lots of papers, but little I can find in terms of
functional tools!

  yours,
      harry

Received on Monday, 19 January 2015 21:11:30 UTC