Re: The Practical Benefits of the Relational Model

Costin Cozianu <c_cozianu_at_hotmail.com> wrote in message news:<3D94EE6E.5020804_at_hotmail.com>...

> To begin with nobody has implemented a relational system as yet.

I suppose the last several years of my life, and the lives of my co-workers were spent doing nothing. I wish people would stop saying that! Just to be perfectly clear: WE HAVE a commercial relational database management system.

> I'm sure we disagree here, although I simpathize your view. Let's be
> clear: I'm not saying that you are wrong. You can define a framework
> (model) in which types are sets of values by definition. Nothing wrong
> with that.

It turns out that we do have different definitions of type after all. I certainly don't consider a implementation contract (interface) a type, and the implementation is (operators are) also orthogonal to type. Mixing them in the way you describe has led to massive confusion on the subject. Unless we can agree about what a type is, additional discussion is likely to be fruitless.

> By the way, how do you define values? As far as Mr. Date is concerned
> the values are immutable and carry their type with them. Kind of
> circular don't you think ?

Type and value are inextricably linked. You can't talk about one without the other.

> But the real question is how useful that system is? (Assuming you can
> get past the circularity between values and types). It turns out that it
> is not really, as you probably found out when you decided not to
> implement features of the type system that are essential.

You are going way overboard here (and in the rest of your posting). We did not "decide" not to implement features of TTM's type model... the actual process was that we put basic scalar types in and it was so easy to provide some of the capabilities of subtyping that we couldn't resist.

--
Nathan Allan