RE: Data storage, data exchange, data manipulation

[Jeff Lowery <jlowery@scenicsoft.com>]

I think it was Tom Passin who pointed out the distinction between conceptual
and physical data models. This would imply conceptual as well as physical
schemas, although I think all schemas to date are schemas that model a user
domain with some physical representation in mind. Can there be a conceptual
Schema? UML may get us close to defining one, but even there I think UML is
tainted by physical model pollution in subtle ways.

So a conceptual schema independent of physical representation is conceivable
to my mind. That representaion would then be transformed to various physical
schemas, although probably not isomorphically.

Now, the rules for defining a conceptual schema based on business domain I
think could be formalized, just like database schemas normalization rules
are formalized. I think a conceptual schema would model a physical reality
in the same way that mathematics models a physical reality (plus some
surreality for good measure).


> -----Original Message-----
> From: Bullard, Claude L (Len) [mailto:clbullar@ingr.com]
> Sent: Sunday, July 01, 2001 1:25 PM
> To: Ronald Bourret; Xml-Dev (E-mail)
> Subject: RE: Data storage, data exchange, data manipulation
> 
> 
> For many reasons, schema design IS an art form, not a 
> science.  Lots of different methodologies can be applied, 
> the conceptualization and schematization based on observation 
> of any domain remains largely a "dealer's choice" then 
> (as in the spelling), a matter of frequency of use.
> 
> Len 
> http://www.mp3.com/LenBullard
> 
> Ekam sat.h, Vipraah bahudhaa vadanti.
> Daamyata. Datta. Dayadhvam.h
> 
> 
> -----Original Message-----
> From: Ronald Bourret [mailto:rpbourret@rpbourret.com]
> 
> Jeff Lowery wrote:
> > I think object-relational databases have some promise. 
> Knowing how to
> > decompose and XML hierarchy just enough to result in an 
> efficient relation
> > model is more of an art than a science right now: I don't 
> think you get
> much
> > benefit if all parent-child relations are rigorously broken 
> down into
> > primary/FK pairs, for instance.
> 
> I think this is very true and will probably remain an art. One
> experience we've gotten from tools that automatically 
> generate database
> schema from DTDs is that it often results in very inefficient storage
> models. 
> 
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