All v3 mods XML Schema documents include a propritary XLINK XML Schema
from the Library of Congress
(http://www.loc.gov/standards/xlink/xlink.xsd), which sadly is
incompatible to the official copy of W3C
E.g. attributeGroup simpleAttrs (W3C) is named simpleLink (LOC)
This is no problem if you embed MODS-Metadata in other LOC-Standards
like METS documents, which use the same schema.
But if you have a custom container which uses XLink too and has therefor
imported the official XLINK Schema the problem starts.
For one Namespace exactly one XML Schema is loaded. Exactly that one
that is used at the highes import level (here custom container). At the
point of importing http://www.loc.gov/standards/mods/v3/mods-3-5.xsd the
official XLink Schema is already loaded so for mods documents in custom
builds xlink:simpleLink cannot be resolved and results in validation errors.
I noticed that the LOC Schema was build in 2004 while the last official
version is of 2008. But I see no reason why the is a need for a custom
incompatible copy of the xlink schema anymore.
It would be great if these issues could be solved somehow - after people
get paid again. One way - that should be compatible - is to re-edit the
XML Schema for MODS that it uses the XLink Schema of W3C.
The other way would require to fork every MODS Schema and use a copy of
it for validating and doing this alike for every release in the future.
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