@fugu13 @garemoko I had been thinking:

* only 'identified' groups should be allowed as query parameters
* 'identified' groups may not have members, so matching on members is irrelevant
* if an actor or identified group passed as a parameter matches exactly, or is a member of an ad-hoc group in the target field in the statement, then the filter condition matches

I suppose the ad hoc groups approach above would be a way to query on multiple actors at once, which might be nice, but it seems odd to have an ad hoc group of [Andrew, Russel, Ben] match a statement that just talks about "Russel".