Re: Navigation vs Relational operators

"Ken North" <knorth2_at_deletethis.yahoo.com> wrote in message news:c88knd$mc9$1_at_ngspool-d02.news.aol.com...
> > In what way is "navigation" different from using relational operators ?
>
> In the data access context, navigation usually refers to:
>
> 1. Record-at-a-time traversal through an ISAM database. You make calls to
a
> database library to get the next or previous record (using sequential or
indexed
> access).
> 2. In a network model database, you navigate through pre-defined sets by
making
> calls to get the next or prior member of the set, or the owner. It's
> conceptually similar to a doubly-linked list.
> 3. Relational is non-navigational. You don't need to know how to navigate
to the
> data that matches your search criteria.
>
> If you tell a taxi driver "Take Hwy 163 north to Interstate 8. Turn west
on
> Interstate 8 until you come to Interstate 5. Turn North on Interstate 5
until
> the split at Interstate 405. Take I-405 North until you get to the West
Century
> Blvd. exit. Turn west and take West Century Blvd. to Los Angeles Airport".
> That's navigation.
>
> On the other hand, if you say "Take me to Los Angeles Airport", that's
SQL. You
> rely on the driver to know the best route.

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 Received on Mon May 17 2004 - 00:23:11 CEST