Re: A numerical methods viewpoint on OO/FP/Relational

In article <3b47185f_at_tobjects.newsource.com>, peter_douglass says...
>
>Might I ask if there is anything in constraint databases which violates the
>relational model?

I'm not sure if this is a valid question. Constraint databases generalise the relational ones. What things could be expresed in Constraint databases and which cannot in the Relational Model?

>If so, is this violation of the relational model
>necessary in order to impose arbitrary constraints on the database?

I thought I answered this one previously. Can Relational answer spatial queries? OK, we'll introduce spatial domains, but then we'll have to introduce spatial operators as well. Constraint databases don't need to program any special operators. It can be viewed as a higher abstraction level.

Assume that I have a system:

x*x+y > 5
y*y-3*x < 3

how would I store it in the relational? By limiting the base facts that can be stored in the relational database, we limit also the class of problems that fit into the model.

It is not all that rosy in Constraints DBs as well. In the above example, am I suggesting that Constraints DB has to be aware of Groebner Basis?

>Leaving theory aside for a moment and looking at commercial products,
>ugliness aside, is it not true that with sufficient effort, one can program
>any arbitrary constraint on a database?

I'm not sure I follow.

>Similarly, ugliness aside, doesn't
>the Turing completeness of SQL (with recursive queries) imply that any query
>can be expressed in SQL?

You are welcome to write a query that returns all numbers from 1 to 1000. I reserve my rights to change the upper boundary. Received on Sat Jul 07 2001 - 21:36:49 CEST