Re: [ubl] Discussion of substitution groups

["Anthony B. Coates" <abcoates@londonmarketsystems.com>]

On Tue, 19 Jul 2005 10:47:52 +0100, CRAWFORD, Mark <MCRAWFORD@lmi.org>  
wrote:

> And if we don't minor version our namespaces?

In transactional messaging, there can be the risk of legal consequences if  
you don't know exactly which version of a message Schema applies to an  
message instance, since each Schema version is like a different version of  
a contract, and you introduce a business risk of you decide do something  
under the terms of a contract, without checking which version of the  
contract actually applies.

The upshot is that each message instance really should identify which  
Schema, and which version of that Schema, applies to it.  The most popular  
way to do this is to have a unique namespace for each version of each  
Schema.  The way I like to do it, sometimes in addition to the namespace  
technique, is to provide top-level attributes which have a fixed value  
that is required to appear, and which identify the Schema and version.   
Sometimes people try to use the 'schemaLocation' to provide Schema version  
information, but this is a fragile technique that I don't recommend in  
general.

So, there is some flexibility in the exact solution that could be chosen  
for this reason (explicit version identification).  I do think we need to  
be thinking of this when choosing the UBL solution.

Cheers, Tony.
-- 
Anthony B. Coates
London Market Systems Limited
33 Throgmorton Street, London, EC2N 2BR, UK
http://www.londonmarketsystems.com/
mailto:abcoates@londonmarketsystems.com
Mobile/Cell: +44 (79) 0543 9026
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