Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
Date: 25 Jun 2005 11:00:35 -0700
Message-ID: <1119722435.810693.78150_at_o13g2000cwo.googlegroups.com>
Jan Hidders wrote:
> Marshall Spight wrote:
> >>It can be. One of the better definitions is found at:
> >>http://www.rpbourret.com/xml/ProdsNative.htm
> >
> > So, I read that page and it really left me with the feeling
> > that I'm right to think that XML doesn't have anything interesting
> > to contribute to the field of data management.
>
> It contributes new problems that weren't there before. :-)
LOL!
> But
> seriously, who claimed that XML would be a better way to model your
> data? I certainly wouldn't. But it's an interesting and important data
> exchange format, and its widespread use will inevitably lead to the need
> to manage data that is in that format. That's all.
What kind of things make it interesting to you?
> > What is the difference between an element and an attribute?
>
> Elements are ordered, attributes are not. Elements can contain complex
> content, attributes only strings.
> > Nowhere on the page did I find a single mention of a type system.
> > How are we going to do data manegement without a type system?!
>
> Sometimes you will have a schema for your XLM documents, sometimes you
> won't. The DBMS should be able to deal with both situations.
> > [...] To start with, I would expect a
> > type system, some relationship mechanism beyond simple nesting,
> > and a standardized way to specify schema, expressed in the metamodel
> > itself (aka a data dictionary.)
>
> Yep. XML Schema does all that. It's a bit, er, bulky, though.
> > I'd be interested to hear what sort of specific things you'd like
> > from a next-generation data model. I'll take a stab and guess that
> > it includes union types; they're on my list as well. What sort of
> > things would you like in, say, the constraint language that would
> > be different? What about the update language?
>
> I think I would first concentrate on the global structure of the data
> model, the associated languages depend on that. Here I have two big wishes:
> 1. I want a data model that is at an abstraction level that is
> comparable to the Entity-Relationship Model.
> 2. I want a data model that is completely unbiased wrt. how data is
> nested. I don't want a distinction like between the relational engine
> and the domain/type engine. When the domains get big and complex and
> queries combine data from different levels, then such a separation will
> make query optimization unncessarily difficult.
Still very curious,
Marshall Received on Sat Jun 25 2005 - 20:00:35 CEST