Re: Example of expression bias?
Date: 21 Jun 2006 08:36:59 -0700
J M Davitt wrote:
> This is confusing; in this post, the posters' name was snipped
> and the quoting indicators seem broken. Going back in the
> thread, I found:
> >>>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.
> > 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.
Received on Wed Jun 21 2006 - 17:36:59 CEST