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

Jon Heggland wrote:

> In article <V4Eue.128061$PH4.7042098_at_phobos.telenet-ops.be>, 
> jan.hidders_at_REMOVETHIS.pandora.be says...
> 


>>>[...] I recently reviewed a 


>>>paper for VLDB which was quite scary in that regard---especially since 

Well, even for an anecdote it's a bit light on information. Basically all I know now is that someone with better qualifications than you said something that you apparently very much disagreed with. I hope you will forigive me that, as long as that is all the information that I have, I think there is a distinct possibility that 'the big name' was actually right.

>>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?

I'll show you mine if you show me yours. :-) Dana Florescu made statements like that in public. Others may also have, I don't remember, but the 'personal experience' I'm talking about was in private conversations, so I'm not at liberty to give you their names. Would you have examples of people in the XQuery or related workgroups that claimed the opposite?

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

It can be. One of the better definitions is found at: http://www.rpbourret.com/xml/ProdsNative.htm

>>>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?

Well, if you want to call it that. But as I said, that name has all kinds of connotations that would not be justified. The data model would be more expressive. The constraint language would be very different. The query language would be very different. The update language would be very different. View definitions would be different. The way that queries would be optimized would be very different. Concurrency control would be different. These are not trivial things. They matter.

>>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?

I'm not sure I understand. Whose motivation? For what?

• Jan Hidders