Re: What to call this operator?

Mikito Harakiri wrote:
> paul c wrote:
>

>>...
>>the place of <OR> in the world puzzles me too.  for one thing it appears
>>to me that it produces the same result of <AND> when there are no
>>attributes in common, ie. cartesian product.  am i wrong?

i gather that you are saying that the definition means i must infer all possible tuples given whatever domains their attributes specify rather than all possible tuples based only on the contents of the origial relations.

just to see if i've got this straight i wonder if you'd check this:

if may leave infinity out of it and if i may assume a common finite domain with symbols for its values of 1 and 2 and if i may order the attributes just for this purpose and i have r1=<1> and r2 = <1> but no common attribute names (ie. disjoint headers) then r1 <or> r2 would be <1,1>,<1,2>,<2,1>, whereas the cartesian product would be <1,1>.

if that's right, then i am a bit happier about <or> in that it doesn't seem to give the same result of <and> (although i can't think of a good reason right now for objecting to that).

>

>>if it does product the cartesian product, is this somehow contrary to
>>orthogonality?
>>
>>so far, the only use i can see for <OR> is as a separate version to
>>double-check the results of <AND> and <NOT>.  or maybe as an
>>optimization on occasion.

i gather you're not pleased with D&D's idea of 'treating operators as relations'. must admit i don't think i understand it entirely. will have to ponder it.

many thanks,
p Received on Tue Jun 28 2005 - 23:45:06 CEST