Re: relations aren't types?

"Alfredo Novoa" <alfredo_at_ncs.es> wrote in message news:e4330f45.0401041127.772a2d23_at_posting.google.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
news:<xMudnTkkUJU2D2qiRVn-uA_at_golden.net>...
>
> > > No, it is not a possible representation of a relation, it is a
> > > description of the structure of a relation.
> >
> > In what way do those THE_ operators fail to represent a relation?
>
> Operators don't make a representation. A representation is defined by
> its components.
>
> But you can encapsulate relations into a scalar.
>
> For instance:
>
> type T possrep { Header relation { ... }, Body relation { ... } };
>
> Now T is a scalar type with a possrep called T which has two
> components "Header" and "Body".
>
> BTW "encapsulate" means nothing but "scalarize".
>
> But it is evident that there are logical differences between T and a
> relation type. For instance:
>
> var a T;
> var b T;
> ...
> a := a join b; // ERROR

Perhaps for T, but not for a relation type.

Scalar is a useless concept. Generic is not. Any specific interval type is a scalar by any definition. However, the interval type generator, tuple type generator and relation type generator have some important things in common. Received on Sun Jan 04 2004 - 22:44:17 CET