Re: Plural or singular table names

"Bob Badour" <bbadour_at_golden.net> wrote in message news:<Xgr8b.225$o11.8839268_at_mantis.golden.net>...

> > Relational operations on vales does not infer constaints. Constraints
> > are checked in assignment operations (database updates).
>
> Thus you are saying that a constraint affects the declared type of a
> variable

Yes, or in other words a constraints affects the database type.

> and that constraint inference only applies to operations on
> variables by which the dbms derives additional variables.

Yes.

> > What I meant is that pi and 3 are different values.
>
> And each has a unique MST.

In a legal type hierarchy according to the D&D model.

It is trivially true because having a unique MST is a prescription for that model, and any type hierarchy in which a value has not a unique MST is automatically illegal.

Eg:

type a = is integer constraint (a = 3) or (a = 4); type b = is integer constraint (b = 2) or (b = 3);

Illegal.

> The declarations above do not declare variables, and I maintain that the
> value 3 has a unique most specific type.

In the D&D model it is true, but we could develop another model in which a value may not have a unique MST.

Regards
  Alfredo Received on Wed Sep 17 2003 - 15:49:48 CEST