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List:       xmlbeans-dev
Subject:    Wildcard matching rule for XML namespaces?
From:       Oliver Newell <olivern () ll ! mit ! edu>
Date:       2007-08-31 19:57:34
Message-ID: 46D872AE.8080409 () wxmail
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Hi - I'm working with a set of schemas that embed numbers of the form 
$major.$minor in the XML namespaces to convey version information. The 
numbering scheme extends to the imported namespaces - not just the 
target namespace of the schema, as shown below. By convention, minor 
numbers are used to indicate changes that are backwards compatible with 
previous versions - /additions/ to the schema. Major numbers are 
incremented when changes are made that break backwards compatibility. 

<?xml version="1.0" encoding="UTF-8" ?>
<WMS_Capabilities xmlns="http://www.opengis.net/wms/1.3"
                  xmlns:gml="http://www.opengis.net/gml/3.1" >
  <Service>
    <Name>Web Map Service</Name>
    <KeywordList>
      <Keyword>Topography</Keyword>
      <Keyword>Contour</Keyword>
    </KeywordList>

    etc.....

  </Service>
</WMS_Capabilities>

I am interested in having the capability for XMLBeans-based applications 
to happily consume instance documents that are produced using new minor 
versions of a schema. I also want to only generating new package names 
for new major versions of the schema. I see there is a facility in the 
XMLBeans configuration mechanism to specify the package names that are 
generated, so I can do the latter. I don't see a way to do the former - 
it seems like some kind of a wildcard mapping rule is needed so that an 
application based on version 1.3 of a schema will know how to unmarshall 
a version 1.4 instance document to the 1.3 data model. In other words, a 
configuration rule that stated something like:

    http://www.opengis.net/wms/1.*   --> mapsTo -->   
http://www.opengis.net/wms/1

so that all versions with major number of 1 map to the same namespace as 
far as XMLbeans is concerned.

The usefulness of the wildcard capability wouldn't be limited to the 
particular $major.$minor numbering approach shown above. It should also 
be capable of supporting some of the W3C namespace versioning practices 
(which tend to embed a year in the namespace). This capability would 
allow for significantly increased system agility as schemas evolve. 
Right now, if I bump a minor version number in a schema namespace, I 
have to make sure ALL XMLBeans consumers are updated to use the new 
namespace, which isn't very practical for the distributed, 24/7 systems 
we are working on.

Is there an existing way to accomplish what I am describing in 
XMLBeans?  If not, is there any developer interest, or can someone give 
me a hint as to how hard this would be to implement? (and where to start?)

Thanks!

-Oliver




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