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email@example.com (Tyler Close) writes:
>But the document itself structures data. The schema for the
>document is a description of how the data is structured. You are
>using a data model. The schema defines the data model.
Most of the documents I create personally have no schema. The data
model is open, defined only by the instance. The code I write for
processing these documents requires no schema. The code has its own
data model, which may or may not resemble the structure of the document.
>When you write code to fetch a string from an XML document, how do
>you know where in the XML document to look for the string? The
>XML specification doesn't tell you where to find the string. You
>must have some kind of data model that tells you where to look for
Sure, but there's no need for me to share that data model. I do
sometimes use XPath, but I never write documents with the XPath data
model explicitly in mind. (I used to write documents with the SAX data
model in mind, and eventually found I'd written myself into an annoying
>If that's your best shot at a definition, you don't have a clear
>notion of what a data model is. Maybe that's why you call it
Honestly, I don't give a damn about what a "data model" in the abstract
is or should be. It's like talking to me about Platonic Forms. (They
really make me laugh.) I'll happily talk about concrete data and how to
represent or process it.
I constantly find that using other people's data models comes at a cost,
often too great a cost. I find that creating my own data models - and
encouraging other people to create their own data models - works a lot
better than trying to get everyone to agreement on a common data model
and then implement it separately. (That seems to be the case even if a
common syntax is part of the package.)
That's my experience. If I lack a 'notion', I can't say it's a 'notion'
I've ever found useful.
Maybe we have a culture clash here. I'm not fond of being told I "don't
have a clear notion", while you seem upset that someone else accuses you
of "conflating data models and schemas ...[in]... ignorance". Working
in markup does seem to change the way people look at information.