Re: Object-relational impedence

Marshall wrote:

> On Mar 3, 8:52 am, JOG <j..._at_cs.nott.ac.uk> wrote:

>>I was hoping perhaps people might be able to offer >>perspectives on the issues that they have encountered.

> Another big difference:

> Object oriented languages work in object-at-a-time terms.
> Even when those objects are collections, if one wants to
> operate on every object in the collection, one iterates
> over the objects in the collection and calls methods on
> those objects one at a time.

> The relational model works in set-at-a-time terms. One
> operates on entire sets at once.

This is a fallacy.
In any system, if I have a set S of tuples (x,y) , and request the following :

{ e IN S : e.x = 123 }

I have to examine each tuple in the set to find those that satisfy the predicate. The satisfying tuples do not appear by magic.

> The two don't fit together very well.

Particular *implementations* of OO prog langs may not fit well with a relational execution engine. But some (OO implemented on Functional programming infastructure etc) fit very well ( "lazy" programming etc) .

Regards,
Steven Perryman Received on Wed Mar 05 2008 - 18:31:32 CET