Re: RA with MV attributes

On Jan 17, 5:43 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Marshall wrote:
>
> > Types may disappear (or not) at runtime; values do not exist at
> > compile time. If we remove this distinction, we remove valuable
> > capabilities from our language.
>
> I don't follow that at all. Types and values just are.

Certainly, in the platonic sense. It is also useful to consider when types and values are reified, and when they cease to be so. In some systems, types may be reified at compile time but not at runtime at all; this is how C works. Values of course are not reified until runtime.

> > Consider the idea of join compatibility. This is violated if we attempt
> > to join two relations each having an attribute of a given name but a
> > different type in each relation. Now, whatever your feelings
> > about how this should be handled, warning, error, whatever, we have
> > to consider the question of when and whether this situation can be
> > detected.
>
> I assume by "different type" you mean neither type shares a subtype
> other than the universal subtype.

Sure. Or perhaps we may be speaking of system that does not have subtyping. Out of curiosity, what does Alphora do? I vaguely recall reading that they abandoned subtyping at some point.

Marshall Received on Thu Jan 18 2007 - 06:18:20 CET