Last modified: 2014-09-01 23:22:39 UTC
I see that there is support for novalue and somevalue snaks in some locations, but it's not complete. For example, ByPropertyValueEntityFinder does not support it, and hence neither API nor special page.
The store already stores non-value snaks. It has no query support for those yet as no code has need for it either. The initial query functionality only allows for property value queries (hence the API is named EntitiesByPropertyValue). More complex queries will be supported after that.
So unless we changed our mind on what we want for our initial query functionality from a product perspective, this should not be picked up any time soon. And if we did change our mind, we should discuss first what we want exactly now.
Adrain: also note that the SimpleQuery special page is only meant to do property value queries. (As is states by the class description.) More complex queries will be supported by a dedicated page (that is, if we allow doing those via a special page at all.)