Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> comp.databases.theory -> Re: Example of expression bias?

Re: Example of expression bias?

From: Cimode <cimode_at_hotmail.com>
Date: 21 Jun 2006 08:36:59 -0700
Message-ID: <1150904219.741842.231350@p79g2000cwp.googlegroups.com>

J M Davitt wrote:
> [snip]
>
> This is confusing; in this post, the posters' name was snipped
> and the quoting indicators seem broken. Going back in the
> thread, I found:
>
> Cimode:
>
> >>>An attribute does not belong to a data type. A data type is the set of
> >>>rules that apply to attribute for saying whether or not values in
> >>>tuples are permissible values in the system.
>
> Tony D:
>
> >>If an attribute doesn't belong (for want of a better word) to a data
> >>type, how do you specify what the acceptable values for it are ? Your
> >>second sentence moves in a single breath from attributes to tuples to
> >>the system as a whole.
>
> Cimode:
>
> > Whatch out with semantics...
> > *belong* suppose EXCLUSIVE relationship between the two...A data type
> > definition may be *mutualized* by several attributes.
>
> How is it that data types constrain values in tuples? Did you mean
> to say values in scalars?

A tuple is nothing but an elementary relvar.

> What, then, does "belong" mean? More to the point, perhaps: what
> does "not belong" mean? Can you elaborate on this "exclusive
> relationship" - that, I presume, you feel does not exist -
> between two... What? Attributes and types?
belong is Tony's term...There is no exclusive relationship between a relvar and a data type in the sense that no one to one relationship cardinality between the two which is implied by *belong* verb semantics. It was a warning on possible ambiguity that could arise from Tony D semantics.

> What is mutualization? How do attributes mutualize types?
They mutualize their defining properties is what I meant.

A many to one cardinality relationship of definition exists between relvars, attribute and data types on the other hand. Several relvars may share the same data type.

> [snip]
Received on Wed Jun 21 2006 - 10:36:59 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US