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Subject: [ver] (AW/Fwd) to consider before call
----- Original Message -----
From: A. G.
To: Stephen Green
Sent: Tuesday, April 12, 2005 1:47 PM
Subject: Re: [ver] Anything to consider before call?
Yes, I think I actually figured out a solution, although i haven't had time to really work up the samples yet.
I was looking at your samples, and I realized that the one thing we do differently in the SDMX implementation of this aspect of NDR (we don't use all the rules, as they don't always apply) is that we have each extendable type represented as the head of a substitution group.
In NS A v. 1.0, I declare Item and Line. Each type is the head of a substitution group.
In NS B v 1.0, I declare the Invoice, as per your example from our earlier call.
If I go to create v. 1.1 of these namespaces, I can extend the Item in NS A v. 1.1, and also extend the Line (which contains the Item). If I indicate that the Item is a member of the Item substitution group, however, then I get the extended version of Item instead of the old one when I create the new Line (which, of course, I use in the new Invoice, which can also be extended).
Had you considered this approach? It has some ramifications, but avoiding the problem you ran into is exactly why substitution groups were invented. I know this was discussed in NDR soime time ago, but it clearly didn't make it into the spec.
I thionk we should discuss this on the call, unless jet-lag is making me miss some obvious flaw.
Stephen Green <firstname.lastname@example.org> wrote: