Brian Selzer wrote:
> "Jon Heggland" <jon.heggland_at_idi.ntnu.no> wrote in message
> news:f1c26e$9nk$2_at_orkan.itea.ntnu.no...
>> I don't think the semantics of key updates is as clear-cut as you think,
>> though. It may seem intuitively obvious that when you update the sole
>> key of a "Person" relvar, you are still talking about the same person
>> (speaking loosely). But this is entity thinking, which is fuzzy, and
>> dangerous to mix with relational theory. I am skeptical as to whether
>> this notion of "sameness" can be formalised, and generalised to the less
>> obvious cases.
>
> I don't think the semantics of key updates is even relevant.
I think it is crucial if you want to claim that relation-based TCs are
less powerful/expressive than tuple-based TCs. And ... Bah. This is just
a rehash of the "Relation Schemata vs. Relation Variables" thread.
Anyone interested in my thoughts can read that one.
--
Jon
Received on Thu May 03 2007 - 07:53:35 CDT
