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1
14th April 05:33
External User
Posts: 1

Multisets and 3VL
Folks,
I've read Date, Darwen and Pascal's ideas on how their relational model is based on set theory (I assume they mean ZFC, but it's probably not important) and twovalued logic, and they've done a thorough job of writing this down. Has anybody done similar work starting from multiset theory and threevalued logic? I'd imagine that since those theories are more general, they limit the things you can say definitively just as neutral geometry has sharper limits on what it can prove than Euclidean geometry does. If such work has been done, can I get a reference to it? Thanks in advance for your help Cheers, David.  David Fetter david@fetter.org http://fetter.org/ phone: +1 510 893 6100 mobile: +1 415 235 3778 You don't need intelligence to have luck, but you do need luck to have intelligence. 

3
14th April 14:45
External User
Posts: 1

Multisets and 3VL
Well, at this stage, it's just fuzzy intuition, but if I had to assign
a reason, it would be that I've noticed that when you "know extra stuff" about a problem domain, for example, that every multiset has multiplicity one, or that truth values will only be in {T,F}, you can then use that knowlege to get to places you couldn't have gotten to if you hadn't have it. Cheers, David.  David Fetter david@fetter.org http://fetter.org/ phone: +1 510 893 6100 mobile: +1 415 235 3778 Yesterday, upon the stair, I saw a man who wasn't there. He wasn't there again today. I think he's with the NSA. 
5
16th April 14:10
External User
Posts: 1

Multisets and 3VL
Actually, one can't. Neutral geometry includes spaces with positive
(aka spherical), negative (aka hyperbolic) and zero (aka Euclidean) curvature. With the parallel postulate, you can prove things that you simply can't prove without it. In this sense, when you're using neutral geometry, you have to "stop short" in places where you could go further with the parallel postulate in any of the above formulations. "Sharper limits" == "Sharper limits on what particular things you can prove using the more general theory." Cheers, David.  David Fetter david@fetter.org http://fetter.org/ phone: +1 510 893 6100 mobile: +1 415 235 3778 Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve. Karl Popper 
