Re: Fwd: [xml-dev] Build applications using the "simplicity stack"

[Arjun Ray <arjun.ray@verizon.net>]

On Wed, 02 Apr 2014 06:35:48 +1100, Stephen Cameron
<steve.cameron.62@gmail.com> wrote:
| On Tue, Apr 1, 2014 at 10:15 PM, Arjun Ray <arjun.ray@verizon.net> wrote:
| > On Tue, 01 Apr 2014 12:35:36 +1100, Stephen Cameron
| > <steve.cameron.62@gmail.com> wrote:

| > | a data-model in XML Format (schema)
| >
| > [...] XML schema formalisms (DTD, RNG, WXS) are for analytic document 
| > structures, not - as far as I know or understand them - for arbitrarily
| > general "data models". 
| 
| [...] These formalisms have types and convey structure and relationships
| between types.

DTD don't have data types at all, besides strings and tokens.  RNG
defers data typing to external libraries.  WXS is fatally infected
with DB-think and thus has some bizarre mishmash.  Anyone remember
gHorribleKludge?  (Hi Amy!:-))

There was room to re-invent SGML notations, but no one (except RNG, in
a sense) went that route.  The ability to represent types _within_ the
formalism is quite limited.

However, the real nub of the matter is that not all data models are
naturally or conveniently reducible to trees, whereas a XML document
is in the first instance a tree, and schemas for XML are therefore for
trees.  The impedance mismatch may be great or small according to
context, but to discount it as inconsequential doesn't strike me as
wise.

| Is there a more suitable formalism for data-models that you make use of?

UML comes to mind.

| An object-oriented formalism, in UML, uses XML for interchange.

With limited traction and success, if Wikipedia is to be believed (and
in this instance, I don't see why not). 

| my concept of leveraging data-models in cost-effective ways, as I tried 
| to give some examples of, is my key point.

Fair enough.  In my work, I've never found schemas for XML instances a
good starting point, or even a vital consideration, in system design.