Re: Plural or singular table names
Date: 12 Sep 2003 09:35:41 -0700
Message-ID: <e4330f45.0309120835.6c08b19b_at_posting.google.com>
"Bob Badour" <bbadour_at_golden.net> wrote in message news:<cPQ6b.668$VW5.62768164_at_mantis.golden.net>...
Sorry, I skipped this.
> > Agreed, and in TTM keys are not part of the relational types (at least
Relational operations on vales does not infer constaints. Constraints
are checked in assignment operations (database updates).
> > Tutorial D's relation type generator doesn't allow to declare
> > in the examples), they are shorthands for database constraints which
> > are part of the database type.
>
> How, then, do the relational operations on values infer constraints?
>
> That's just a matter of shifting a couple productions around in the grammar.
Of course, but the author's intention seems clear.
> > I find the idea of values having constrains as an absurd. Values are
> > constants. We can not constraint a constant.
>
> People do it all the time.
>
> const float pi = 3.14159;
> const unsigned int three = 3;
What I meant is that pi and 3 are different values.
If you have a variable holding the value pi, and you change it by the
value 3 then pi is still pi and 3 is still 3.
> Even in TTM literals are typed, and types are constraints.
Here you are playing with ambiguous terms.
constants have types
types are constraints
constants have constraints
Both premises, the derivation rule and the conclusion are sloppy.
Using a better terminology (but not a lot better), the conclussion is different.
a constant belongs to N types
types are sets of constants (among other things)
type constraints define which constants belongs to a type
the membership of a constant to a type is defined by the type's constraints
It seems a little more reasonible to me.
Regards
Alfredo
Received on Fri Sep 12 2003 - 18:35:41 CEST