Hey Bryan:
Let me try to sooth your headache with my Substitution Groups 101 articles.
Just settle back, Tuborg glass in hand:

Subtyping in W3C XML Schema, Part 1
Three Degrees of Inheritance
http://www.tdan.com/view-articles/7185

Subtyping in W3C XML Schema, Part 2
Extensions in another Namespace
http://www.tdan.com/view-articles/7186

JAXB, and especially XMLBeans, make light work of generating Java classes
for such XML Schemas.  I know back in the Stone Age RPC Encoded Web services
gave data binding a bad name and the major relational DBMS vendors have paid
scant attention to SQL2 let alone SQL3, but if you stick to basic bread and
butter data types, like UN/CEFACT ebXML CCTS (ISO/TS 15000-5) Core Data
Types, then life's really not so bad - unless you are looking to pick nits
and score points.

Substitution Groups are also a great way to extend data exchange
vocabularies across namespaces for local communities of interest, à la
OAGIS.

Cheers

Jack Lindsey


-----Original Message-----
From: bryan rasmussen [mailto:rasmussen.bryan@g...] 
Sent: Thursday 27 November, 2008 04:51
To: rjelliffe@a...
Cc: xml-dev@l...
Subject: Re: [xml-dev] XML Schema: "Best used with the ______ tool"

>
> On the immediate issue of XSD, there is no technical reason to disallow
> support for element substitution groups for data-binding, as far as I can
> see. A schema that uses them can be transformed into an equivalent schema
> that uses them: in this particular case I don't see why they technically
> provide any obstacle to databinding tools, since they don't rely on any
> target capabilities (i.e. they are an injection mechanism, not a different
> component IYKWIM.)

I think a reason why Substitution groups might not be widely supported
with databinding tools (not actually sure if they are or not because I
don't use databinding) is simply that back when databinding was the
hip way to solve programmer XML headaches substitution groups were
underutilized (which I understand, the syntax always gives me
headaches) and probably it was not implemented as being unimportant or
put on a to do list.

by the time that substitution groups became important - GML, XBRL...
the shine was off of databinding.

Cheers,
Bryan Rasmussen

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