Unique Name Assumption "He cites an OWL Flight paper that caused me quite some headache a few weeks ago (cause there was so little in it that I found to like)...There was an OWL requirement that gives a short rationale for the UNA, but it seems it is not yet stated obvious enough."
The main problem was that the expression of this did not seem to be sufficiently addressed - especially as it is such a basic concept and that there wasn't a simple concrete example (unlike the Cain/Kain and Able one given).
The initial problem was cardinality and OWL Flight attempts to solve the problem with cardinality. Paul put it succinctly: "So what is the point of statements with the owl:minCardinality predicate? They can't ever be false, so they don't tell you anything! It's kind of like a belt and braces when your belt is unbreakable."
"OWL-Flight and proponents of UNA actually forgot that it's a Semantic Web, not just a Semantic Knowledge Base. If you want UNA, take your Prolog-engine. The Semantic Web is more. And therefore it has to meet some requirements, and UNA is an astonishingly basic requirement of the Semantic Web. Don't forget, you can create local unique names if needed. But the other way would be much harder."
The statement of the problem and a solution seems to be better explained elsewhere and I did comment that the resolution, local unique names using AllDifferent, didn't actually seem to solve the problem well enough (without consideration for scalability for example). I have a feeling that context is a better solution to this problem (that might just be my golden hammer though).
"Still, Andrews arguments lead to a very important question: taking for granted that Andrew is an intelligent guy with quite some experience with this kind of stuff, how probable is it, that Joe Random User will have really big problems with grasping such concepts as non-UNA? How should the primers be written? How should the tools work in order to help users deal with this stuff - without requiring the user to study these ideas in advance?
Still a long way to go."
I would agree - this was my main problem - how do you explain to Joe (and Andrew) that all his CDs are the same rather than different. In Joe's experience things are usually different until you start comparing them and then he finds similarities (or like Ernie putting away toys). This is a good example of why the Semantic Web is not AI - it's not trying to emulate the way people think.