Actually, there is not, to my knowledge, a one-to-one relationship between target namespaces and schemas.  For example, versions 3.0 through version 3.3 of MODS all declare the same target namespace:  http://www.loc.gov/mods/v3.  But each is represented by a different schema (or version of the mods schema).  The case is even more complex for xlink, for which there is no normative schema--users have been left to role their own implementations of xlink.  But as far as I know, all implementations of xlink are supposed to be declaring the same target namespace regardless of the particular implementation of xlink they reference.  Initially the MODS and METS schemas imported different xlink schemas, although each was identified by the same target namespace.

My initial question has little, if anything, to do with the target namespace URI--but rather with the very issue that Karen brings up in her response to my original query.

Rick Beaubien

Houghton,Andrew wrote:
[log in to unmask]" type="cite">
From: Metadata Object Description Schema List [mailto:[log in to unmask]] On
Behalf Of Karen Coyle
Sent: Friday, March 13, 2009 4:53 PM
To: [log in to unmask]
Subject: Re: [MODS] URL for the current version of mods

Andrew, it sounds like you are saying that there shouldn't be a generic
URL... ? I believe that people asked for it in the past, but maybe it's
not a good idea. It seems to work when updates are backward compatible
but not when they aren't.
    

No I'm not saying that there should not be a generic URI to the MODS 
XML schema.  Having a generic URI is useful especially when you want to
link to the latest specification.  However, I was saying that:

1) The generic cannot be used in the xsi:schemaLocation attribute for
   MODS instance documents because the attribute uses a specific MODS
   namespace and the XML schema returned by the generic URI could be
   any MODS namespace.  There is a one-to-one relationship between a
   namespace and its schema.

2) The LC web site does not indicate that the MODS generic URI is a URI
   alias of the latest MODS XML schema and use appropriate HTTP status
   codes and headers to indicate that the generic URI is returning the
   representation of the latest MODS XML schema.

These two issue, I believe, led to the confusion of the original poster
asking whether they should or should not be using the generic URI in
the xsi:schemaLocation attribute in their MODS instance documents.


Andy.
  

-- 
Rick Beaubien
Software Engineer, Research and Development
U.C. Berkeley Library

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