> > The part I'm not getting is why this thread is discussing > application-specific requirements for structural constraints on data > > without reference to BIBFRAME profiles, which are _all about_ specifying > structural constraints on data. > > Because this thread, to my understanding, isn't about structural > constraints at all, and never was. Structural constraints are an > interesting topic, but as I understood Rob Sanderson's original critique, > the question of "types vs. properties" isn't about constraint at all. It's > about extension. > Yes, precisely. The constraints are a distraction that came in from the discussion over whether it was a good idea to *require* inferencing or not. Rob -- Rob Sanderson Technology Collaboration Facilitator Digital Library Systems and Services Stanford, CA 94305