# Re: Mixing OO and DB

Date: Sun, 23 Mar 2008 18:39:49 -0700 (PDT)

Message-ID: <78b8d233-984e-4ce1-8f44-7d3d4b65fe4d@n58g2000hsf.googlegroups.com>

On Mar 22, 2:28 pm, "Dmitry A. Kazakov" <mail..._at_dmitry-kazakov.de>
wrote:

*> On Fri, 21 Mar 2008 22:42:44 -0700 (PDT), frebe wrote:*

*> >> The claim that the application can't do translations is*

*> >> incorrect, on its face. SQL isn't going to return DAGs, or even*

*> >> queues, stacks, or maps.*

*>*

*> > A DAG can obviously be represented as a set of tuples.*

*>*

*> LOL. For that matter, a DAG can be represented by a natural number. This by*

*> no means imply that ALU were operating DAGs, or that the ADD instruction*

*> would return DAGs. You could certainly represent DAG by used paper cups...*

You seemed to have missed the point that a DAG _is_ a set of tuples. To a mathematician, creating a DAG using pointers and memory addresses isn''t much different from using paper cups connected by bits of string.

*>*

*> > The same*

*> > applies to queues, stacks or maps, even though I can't really see why*

*> > you need a low-level data structure like a map, when relations are*

*> > availible.*

*>*

*> Because an algebraic structure is not just a set. Isomorphism of elements*

*> does not make algebraic structures same. Is it so difficult to grasp?*

*>*

*> P.S. To the list of problems I put before you to solve:*

*>*

*> (Message ID: 16zwfmkrguxvp.xiq5rgz36sbc...._at_40tude.net)*

*>*

*> 10. Let G be a DAG. Compute G* (transitive closure).*

Just use a recursive join. I fail to see the big deal.

*>*

*> --*

*> Regards,*

*> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de*

Received on Sun Mar 23 2008 - 20:39:49 CDT