Re: Navigation vs Relational operators

Interesting discussion.
The idea of suggesting a route to the taxi driver is like suggesting index usage to some DBMS. Sometimes we force a specific order of operation by placement of subqueries. In any event, the DBMS/taxi driver makes the final decision about how to get the data.
And remember that in many situations, the data is no where near where you think it is. Think "bufferpools" or other caching ideas. In other words, "LAX" isn't always at the same location, so for you to force the taxi driver to take a specific route might be the worst idea possible.

-- 
Mike Nicewarner [TeamSybase]
http://www.datamodel.org
mike_at_nospam!datamodel.org
Sybase product enhancement requests:
http://www.isug.com/cgi-bin/ISUG2/submit_enhancement

"x" <x-false_at_yahoo.com> wrote in message news:40a884b6_at_post.usenet.com...


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> "Gene Wirchenko" <genew_at_mail.ocis.net> wrote in message

> news:99bga0l4713o8g0r5krejq7ldchniifrgh_at_4ax.com...

> > "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote:

> >

> > [snip]

> >

> > >I dunno about that -- it seems to me that if you say "Take me to LAX"

and


> > >you take me down all of these streets until we get there -- that is


> > >navigation.  I didn't need to know how to get there, but someone did.

> > >

> > >If you say "Take me to LAX" and you don't navigate there, but rather

use


> > >some set operations to beem me up to LAX, then that is relational -- no


> > >visible navigation because no navigational operators were employed by

> anyone

> > >including the taxi driver.

> > >

> > >Or am I missing the point?  --dawn

> >

> >      I think so.  In the second case, the transporter operator would

> > know what to do.  In the first case, the taxi driver is analogous to

> > the DBMS.  In the second case, the transporter operator is analagous

> > to the DBMS.  In both cases, we do not need to know how they do what

> > they do; we just specify the desired result.

> >

> >      The navigation (or whatever the execution is called) is hidden

> > from us.

>

> Well, we don't need to tell the driver how to drive.

> But we may need to tell him (some of) the route ...

>

>

>

>

>

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