Re: Generic Modeling

D_at_B.A wrote in message news:<z82Z7.2503$cD4.4766_at_www.newsranger.com>...
> In article <60360d48.0201022255.b17627a_at_posting.google.com>, Brian Smith says...

> >Futher, I don't doubt that a RDBMS could be built on top of an OODBMS;
> >similarly, I think that you could be an OODB system that stored
> >information in an underlying RDBMS.
>
> Building one thing on the top of the other can't hardly be anybody's
> motivation.

I was trying to hint that an RDBMS isn't necessarily more powerful than an OODBMS and vice versa, by saying (but not proving, obviously) either one could be implemented by the other.

> I would like to see how would you query the equipment scattered at various
> levels of the hierarchy in OODB.

So would I.

> >I know you can do this really easy by using a "THING" table in SQL,
> >because I have already created something like that using two tables.
> >For the deep copy it helps to have a recursive query operator like the
> >Oracle "CONNECT BY". Then you just do an INSERT INTO ... SELECT ...
> >CONNECT BY ...
>
> One more time, the more obscure concept of the language you use the more
> chances are that optimizer doesn't supports it yet. Hierarchical subqueries
> are not unnested by optimizer, for example.

Well, in very limited testing, Oracle9i was able to do a pretty good job with my hierarchial query, and it included an outer join and three inner-joins between two tables, along with a DISTINCT clause to filter out duplicates (I didn't have a hierarchy, I had a directed graph, so I needed DISTINCT to filter out the items that were part of multiple "hierarchies" in the graph). But, I will have to see how my prototype system scales when presented with a larger amount of data.

Thanks,
Brian Received on Thu Jan 03 2002 - 23:24:30 CET