On Tue, Aug 19, 2014 at 5:59 PM, Markus Krötzsch <markus@semantic-mediawiki.org> wrote:
I guess it is related, yes. Although currently I am first focussing on efficient query answering -- inference will come after that :-) Whether one stores the results in a database or not is an implementation detail, btw., that is maybe not essential for a user.

Ok, ok, no hurries :-) 

Oh, and of course all of this seems to be rather off-topic for the current subject "Commons Wikibase" :-) All that is relevant there has already been said I guess ("many categories could be expressed by queries to improve results; a gentle, community-led transition will be possible and preferred; categories won't be switched off just because Wikidata is switched on").

Actually I have one last question :)  At the moment Gerard is using "is a list of:<value>" on category item pages which has the effect of being the inverse of "instance of". And then he adds further conditions as qualifiers, see:

While this method of works for simple categories, more complex ones would be hard to model using this method, like

I was thinking of modelling it like:
<Category:Discoverers of extrasolar planets> is a list of <human>
<Category:Discoverers of extrasolar planets> has items used as value of <discoverer>

Of course it would require to have a link between the item "discoverer" and the property "discoverer", but would that make sense?