OK, here is my current top-candidate:
When classifying types it is often necessary to match against several variations of one aspect.
There are special variations which make this possible. These are called *abstract*.
The most important case is to match any variation; that is, to ignore that aspect in the context of type classification. Because of this, every aspect has at least one abstract variation named "unspecified_" plus the aspect name.
That one also makes sense to me, I'm still not sure that "abstract" is the right word though :-) Explanation: to me if something is "abstract" then you need to add something to it, extend it in some way to make it concrete. What you're doing is combining several concrete definitions to form a non-specific union of some kind. So a quick trip to thesaurus.com suggests: "composite", "compound" or "mixed" as possible names, do any of these work for you? John.