Re: Relational Database vs. Nonrelational

["Wilcox, John (WWC, Contractor)" <wilcoxj -at- WDNI -dot- COM>]

> ----------
> From:         Elna Tymes[SMTP:etymes -at- LTS -dot- COM]
>
> > Can anyone out there give me information on differences between a
> > relational database vs. nonrelational?
>
> Think of the difference between data on a tape (linear) and data on a
> disk (non-linear, usually).  The older, linear databases used files
> that
> started with some header descriptor, then associated data in a series
> of
> fields.  Within a set, all records had the same fields, regardless of
> whether they had data.
>
> With relational databases, fields can be used in a number of ways (and
> can be of variable length), provided that they are linked in tables.
> Rather than looking up the field in each record, you request data in a
> named field in a named table.   Where the data happens to be stored is
> pretty much irrelevant.
>
> With object-oriented databases, you again are not limited by the size
> or
> physical location of the field, but in addition your fields can have
> inheritance.  In other words, if you're working with an airline
> scheduling program, for instance, the field "Crew" can inherit the
> characteristics of the type of plane - you'll need fewer people for
> some
> kinds of planes than for others.
>
There are two other types of database that I know of -- hierarchichal
and network.  Briefly (and as I understand it), the hierarchichal is
similar to the object-oriented model, with the major exception of
inheritance.  The relational model is the only one of the four types
that doesn't provide database navigation through related objects using
direct pointers.  Instead, it uses redundant keys stored in separate
index files.  (That's why Microborg Access is so slow.  But, of course,
it's popular anyway, just because it's Microborg.)  The network model
(not the relational model -- sorry to have to disagree, Elna) is the
oldest of the four types and is still the most efficient, both in access
time and disk space used.

AFAIK, the leading vendor of network-model database products is Raima,
so you can look to them for further info (www.raima.com).  Their latest
DBMS is called Velocis, which actually combines the best features of
both the network and relational models.  I'm not currently associated
with Raima, but I was the lone TW there in 1987-88.



Regards,

John Wilcox, Documentation Specialist
Timberlands Information Services, Application Delivery Group
Weyerhaeuser, WWC 2E2, Box 2999
Tacoma, WA 98477-2999 USA
253-924-7972  mailto:wilcoxj -at- wdni -dot- com
(I don't speak for Weyerhaeuser, and they return the favor.)