Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: Jon Heggland <>
Date: Fri, 24 Jun 2005 16:43:47 +0200
Message-ID: <>

In article <V4Eue.128061$>, says...
> > Would that it were that simple. The same could be said about the "XML
> > data model", yet well-known researchers are happily reinventing the
> > square wheels of IMS and similar systems, apparently blissfully unaware
> > of the history and fate of hierarchical databases. I recently reviewed a
> > paper for VLDB which was quite scary in that regard---especially since
> > another reviewer, a really *big* name, said it was the strongest he had
> > reviewed.
> That's quite possible, but since I don't know the details I couldn't
> possibly comment.

Yeah, I know it's anecdotal.

> On the other hand, I know from personal experience
> that even some of the big names that are right at the core of the hype,
> are very clear about what they think XML is useful for what it is not
> useful for, and who would judge any claims that it would somehow replace
> the relational model as, and I quote, ridiculous.

Which big names are those?

> In that respect I really like the work by Torsten Grust et al that shows
> that you can do XML on top of an RDBMS, and that even though you are
> pushing the square XML peg in the round RM hole, you will still get
> something that works in many respects better than XML-native solutions.

I've often wondered what exactly *is* an XML-native solution. Is it storing everything as text files?  

> So even if you are basically horribly abusing the RDBMS and shoving all
> that vile XML stuff down her throat, which it was not really built for
> in the first place, she will still happily and with a smile on her face
> provide you the scalability that we have become so accustomed to. Almost
> brings tears to my eyes. *snif* :-)

Well, if you just treat XML document as a data type, there is no abuse involved. The RM *is* designed for this.

> > The
> > question is whether such models are different *enough* from the network
> > model(s) to make it worthwhile to distinguish between them. The concept
> > exists, but that in itself does not mean very much.
> I don't completely agree that this is the right question. What has
> changed is not so much the data model, but the whole cloud of knowledge
> and silent assumptions that surrounds it. For the network model it was
> usually assumed that you wouldn't need query optimization. That
> data-independence was not possible or just a nice-to-have. In the
> beginning some also thought that about OODBs. That, in my experience,
> has changed.

So it is a renaissance of the network model?

> > (Another point is the question of what "OO" in that context really
> > means---the paper does not mention encapsulation, polymorphism or
> > inheritance. What is an object?)
> Well, the main reason for that is that these aspects are not relevant
> and somewhat orthogonal to the problem that it studies. I think I have a
> pretty good idea of their view on that, though.

Ok ... but I though half the point of OODBs was to lessen the "impedance mismatch" between procedural OO programming languages and declarative databases (by making the databases less declarative). What is the motivation now?

Received on Fri Jun 24 2005 - 16:43:47 CEST

Original text of this message