Re: The BOOLEAN data type

71062.1056_at_compuserve.com (--CELKO--) wrote in message news:<c0d87ec0.0304021744.46f642ba_at_posting.google.com>...
> >> But the problems are on nulls, not on the boolean type. <<
>
> If you had a "Chris Date Database" without NULLs, you would not need
> the 3VL and could build a consistent model.

I have two, and yes it is a lot more consistent model.

> >> SQL is clearly bad founded and the boolean type is the most
> fundamental type of all. <<
>
> No, it is more complex to try to model the real world, where you don't
> have perfect knowledge and attributes can be missing.

I don't see your point.

> There are many
> versions of Geometry -- on a plane, a triangle always has 360 degrees;
> on the surface of a sphere, a triangle always has more than 360
> degrees; on the surface of a hyperbola, a triangle always has less
> than 360 degrees.

The above statements are True, a boolean typed value :)

> The Catholic Church in the Middle Ages was sure
> that ONLY Euclid was right. This made navigation with a round Earth
> into heresy.

And what is the relation with the boolean type?

For instance I could create a relation variable like this:

var Statements real relation { Statement Char, IsHeresy Boolean }

    key { Statement };

And to assign a value to it like this:

Statements := relation {
  tuple { Statement 'Navigation with a round Earth', IsHeresy True },   tuple { Statement 'Earth is flat', IsHeresy False } };

The veracity of the propositions is my problem, the DBMS only have to check the consistency of the propositions, and they are consistent.

Regards Received on Fri Apr 04 2003 - 03:56:47 CST