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Re: [xml-dev] Designing XML to Support Information Evolution
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We are finding there are two different
drivers in the XML usage:
*) exchange, actually exchange of (roughly)
the same data in different contexts, across different systems and organizational
boundaries.
*) as the 'evolved' information itself
- representing the gained functionality and value with which key business
entities emergy from being orchestrated within an environment.
The later, with audit trails and the
need to reproduce that context at some later date, has been where i've
seen production relational environments become cumbersome.
Requirements grow and change and/or
success increases scope for a relational model over time and - all too
often - dull the design intent under which the relationships were modeled
making each new integration more brittle, the model less normalized based
on competing access paths.
We have found good success with a mixed
design using versioned xml for the transactional context with only key
relationships between key entities are expressed in a way of which Codd
or Date would approve.
Context and hierarchy seem to serve
well within a business transaction - relationship better serve in comparisons
and analysis across those transactions. We are not having great success
with xquery for the later, not yet anyway, though the tools in this arena
continue to improve.
/james
| Michael Champion <mc@xegesis.org>
05/17/2004 10:28 AM
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Subject
| Re: [xml-dev] Designing XML
to Support Information Evolution |
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On May 17, 2004, at 10:20 AM, Roger L. Costello wrote:
>
> 1. How you structure your information in XML has a tremendous impact
> on the processing of the information.
>
> 2. Hierarchy makes processing information hard! There exists a
> relationship between hierarchy of information and the complexity of
> code to process the information. The relationship is roughly: the
> greater the hierarchy, the greater the complexity of code to
process
> the information (Some hierarchy is good, of course. But
the amount
> of hierarchy that is good is probably much less than one might
> imagine, certainly less than I thought, as described above.)
>
> 3. Flat data is good data! Flatten out the hierarchy of your
data.
> It makes the information flexible and easier to process.
>
> 4. Order hurts! Requiring a strict order of the information
makes for
> a brittle design. It is only when I allowed the lots and pickers
to
> occur in any order that the flexibility and simplicity kicked in.
>
> Comments? /Roger
I'm wondering if you haven't rediscovered the relational model? (Or
at
least you've discovered the importance of "normalization" in
the
relational sense even in the XML context). But why bother with XML
at
all (except maybe as a data interchange format) here? Wouldn't a
relational reporting tool be much easier than XSLT with this data
structure?
C.J. Date gave a speech recently
http://searchdatabase.techtarget.com/originalContent/
0,289142,sid13_gci962948,00.html complaining that XML is trying to take
over the world. Maybe he has a point :-) I certainly don't
agree with
all he's saying, but if you are modeling data rather than exchanging
documents, I would think that the relational model would be the
starting point until you run into its walls.
Clearly if flexibility is paramount, order and hierarchy are a pain,
and there's not much gain *if* you have unique identies for everything
and the identity is all you need to know to figure out what to do with
the information.
On the other hand, if *context* is important, i.e. the intepretation
/
semantics / meaning / processing paradigm of some bit of information
depends more on where it stands in relation to other information, then
order and hierarchy are critical. That's where the XML "data
model"
(by which I mean "fairly deeply hierarchical labelled trees in which
order is preserved", not the InfoSet per se) comes into its own.
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