Re: Canonical DB
Date: Sat, 24 Jun 2006 14:18:26 +0200
Dmitry A. Kazakov wrote:
> mAsterdam wrote:
>> ...A correct model would have the constraints >> in place to preserve the invariant of the >> structure while allowing all valid modifications.
> Yes. But the problem is (apart from expressing the constraints, which
> itself might be far from trivial: like an acyclic graph constraint etc),
> that you might lose the structure.
LSP? Label-switch path as in
> You have some set of things (whatever they be, relations or
> ellipses) with some structure (algebra), you put a constraint on the set
> (so you get graphs or circles), and see that some statements about the set
> become wrong.
Yep, same thing happens if you fail to put on a constraint which should be there.
> My favorite examples always integers, sorry. (:-)), Put n>0 on integers and
> you will lose negative inverse.
> The point is that it is really, really fundamental. Circles aren't ellipses
> though any circle is an ellipse. The structure is different. Same with
> trees vs. tables.
>>I tried modeling the C3 MRO relationally >>but haven't found a solution (or the conviction >>that it can't be done) yet. >> >>http://www.python.org/2.3/mro.html >> >>and (background) >> >>http://www.webcom.com/haahr/dylan/linearization-oopsla96.html#C3-line >> >>It is a nice (and IMHO very useful) challenge. >>Any takers?
> Ah, multiple dispatch, it is a hard problem. I'm unsatisfied with presently
> existing solutions.
> BTW, it might be interesting to consider relational structures of types.
-- "The person who says it cannot be done should not interrupt the person doing it." Chinese Proverb.Received on Sat Jun 24 2006 - 14:18:26 CEST