Re: Fraud Number 3: U-Gene

Bob Badour wrote:
> Tony D wrote:
>
> > Cimode wrote:
> >
> >>First, I am aware of Date's definition and I do not quite feel
> >>confortable with it because it focuses too much on structural
> >>definition and not enough on the characteristics values extraction from
> >>domains. Neverthless, Date's is logically correct: it's a matter of
> >>perspective.
> >
> > Well that's reassuring; although you're right on the potential for
> > overemphasising structure.
> >
> >>I also believe some of Date's definition can also lead to
> >>confusion..For instance, Date's definition relvar could lead to
> >>confusion with the definition of an attribute. (both have a name, a
> >>data type and may hold a value in time). If we define, attribute and
> >>relvar alike, one take the risk of confusing them...
> >
> > But I'm not sure how you could confuse an attribute with a relvar. A
> > relvar is a variable and can indicate different values at different
> > times. A relation value is value; like an integer value, it never
> > changes.
>
> Ah, but an attribute is a variable a la predicate calculus. See 'bound
> variable' and 'free variable' for what I mean.

Obvious.
An attribute is nothing but an single-domain elementary relvar whose values are defined by data type definition. Confusion made by Tony D is that values holding place in relvars change: they don't --> they belong to a domain from which they are simply extracted. Received on Sat Jul 01 2006 - 15:29:35 CEST