Re: object algebra
From: Eric Kaun <ekaun_at_yahoo.com>
Date: Wed, 03 Mar 2004 13:25:04 GMT
Message-ID: <Q0l1c.55379$tJ6.2298_at_newssvr33.news.prodigy.com>
Date: Wed, 03 Mar 2004 13:25:04 GMT
Message-ID: <Q0l1c.55379$tJ6.2298_at_newssvr33.news.prodigy.com>
"Neo" <neo55592_at_hotmail.com> wrote in message
news:4b45d3ad.0402281221.431f280_at_posting.google.com...
> > The above isn't a "patch for" nulls. What does "weaker relationship"
mean,
> > though? I have no idea how to address that one.
>
> Given EyeColor = {red, brown, N/A} and the table:
> Person EyeColor
> ------ --------
> John N/A
> Mary N/A
>
> A query to find persons with equal eyeColor returns: John & Mary.
Again, when defining a domain (which can be tricky!) you define the operations over it. You sometimes need to do that when representations (POSSREPS) are different, though I'm oversimplifying this whole thing in the interest of brevity. Received on Wed Mar 03 2004 - 14:25:04 CET