Right now we have URL http://wikidata.org/entity/Q1 resolve to real data page. However, a lot of other URLs mentioned in RDF dumps do not correspond to anything. Specifically:
http://wikiba.se/ontology - ontology base
http://www.wikidata.org/prop/ - all property predicates
http://www.wikidata.org/entity/statement - all statements
http://www.wikidata.org/value/ - prefix for RDF values
http://www.wikidata.org/reference/ - prefix for RDF preferences
We should devise and implement URL scheme in which, at least on wikidata, all these URLs would exist and lead to a sensible place.