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RE: ISSUE-20: Extension of collections

From: <paul.downey@bt.com>
Date: Wed, 22 Feb 2006 17:39:14 -0000
Message-ID: <2A7793353757DB4392DF4DFBBC9522550276F388@I2KM11-UKBR.domain1.systemhost.net>
To: <erikj@epicor.com>, <public-xsd-databinding@w3.org>

Hi Erik!

I agree that Versioning and Extensibility do often become confused,
but they are closely related. 

One way forward is for us to anoint one or two of the Schema 
Versioning Use-Cases identified in this document:


"Object Oriented" springs to mind for this WG, 
though "Ignore Unknowns" is the end-game.

I like the idea of only providing a patterns using '##any'.


-----Original Message-----
From: public-xsd-databinding-request@w3.org on behalf of Erik Johnson
Sent: Wed 2/22/2006 5:05 PM
To: public-xsd-databinding@w3.org
Subject: RE: ISSUE-20: Extension of collections

I don't know if I have a great solution here, but it seems like
extensibility and versioning are being muddled.  By versioning, I mean
having some definition of backward and/or forward compatibility between
two or more schema types.  The same compatibility would have to exist
between the corresponding class types.  Since most languages do not have
specific mechanics for versioning, is it even possible to project a
versioning scheme from a schema set to a language in a meaningful way?  

I agree that it would be very good to specify best practices for schema
evolution (how to maintain backward compatibility, when to change the
namespace name, etc.) and give serializer guidance about how to
process/ignore "extra" nodes and when to give up trying to match the
payload with class members.

Also, I don't see a problem with using xs:any and mapping that to a
generic type (like "object").  But the "namespace" attribute is a
problem because (in most languages) there is no way to constrain a class
member to be any type within a certain namespace.  Should the guidance
avoid using namespace attribute values other than "##any"?

- Erik
Received on Wednesday, 22 February 2006 17:39:24 UTC

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