It was an abstract question, we are nowhere like having Wikidata based on an ontology and this obviously won't happen anytime soon. And like GerardM said, no tools; no use. (I might write a javascript gadget or something in the future, but nothing done yet).
On a more general matter of speaking : I don't agree totally with you, as we need some protections to some vandalism possibilities, and that some domains are really easily modeled. There is a lot of properties and it's not always clear wich one to use, and users needs some guidance, which could be handled so much easily if they are pushed to do the good choice at the very beginning by a little push of the sofware, which is a lot easier if we have a model of the domain for a start.
Anyway Wikidata's data still needs a lot of santiation before any use outside Wikipedia or other Wikis (this is also true IN wikidata but the infoboxes are a precious hint - of, my data do not appear in the infobox, what did I do wrong ?). But even like that, what a user might thik is "I don't understand anything F** this project"). Wikidata and Wikipedias rely on good will, please don't forget the user experience.
Yet the query engine is a big missing peace of the puzzle, a query is a model in a sense, so anything that do not fit in a query is something that need to be looked at, but a query happens after a user has entered is data.