How can I constrain publicly available schemas?

[Fraser Crichton <fraser.crichton@solnetsolutions.co.nz>]

Hi,

I'm working on an application where I need to use subsets of publicly 
available schemas.

For instance, to model contacts information I'm using xCIL however xCIL 
has a very large range of formats, for instance one of the immediate 
children the CustomerDetails element can be either OrganisationInfo or 
PersonInfo. My system, however, only wants to process PersonInfo 
elements and never OrganisationInfo so, do I -

a) create a more specific schema using the xCIL namespace (!) (if so, 
should I then validate it twice - once against xCIL and then against my 
more specific schema)

b) XML.com has this article - Designing a New Schema with XML Design 
Patterns - http://www.xml.com/pub/a/2003/06/04/patterns.html - which 
would seem to suggest selectively reusing types and global elements from 
other namespaces, are there any problems with this approach?

c) is the schema just a contract and I should use something else again 
for validation?

Is this a dumb question or has anybody else come across this issue and 
if so how have they approached it?

Cheers,

Fraser


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