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Wolfgang - several of use here are looking into this (trying to decide
whether we still need a separate XLink schema, etc.) but using a different
namespace is not an option.

There's some history here, not all of which is necessary to describe, but to
summarize: we originally DID use a homemade namespace, and found that
stylesheets would not function properly, and further, that using a namespace
other than the W3C XLink namespace for an XLink schema violates the XLink
standard. 

--Ray

> -----Original Message-----
> From: Metadata Object Description Schema List
> [mailto:[log in to unmask]] On Behalf Of Wolfgang Koller
> Sent: Monday, March 21, 2011 10:48 AM
> To: [log in to unmask]
> Subject: Re: [MODS] Problems with Import(s)
> 
> Dear Ray,
> 
> thanks a lot for the explanation. These are all good reasons for you
> doing so, however that still doesn't solve the problem that mods is
> simply incompatible with other schemas which import from the original
> location if a more or less strict validator/parser is used.
> 
> Have you ever thought about adjusting the namespace so that it actually
> uses a custom one? (you can argue if that is correct since it is just a
> second workaround, but in your case it would greatly improve the
> interoperability with other schemas).
> If xlink is a custom version, I think it would be even more correct to
> use a different name space there.
> 
> After all importing different schemas into the same namespace is often
> not supported because for many parsers the same namespace means the
> same schema location (AFAIK the behavior for different schemas imported
> into the same namespace is undefined by the standard). If the parser is
> graceful and tries to parse both schema locations it will result in
> errors complaining about re-defined elements (because your schema is
> not an addition but a copy).
> 
> Best wishes,
> Wolfgang
> 
> 
> Ray Denenberg, Library of Congress schrieb:
> > The xml.xsd question is more easily answered. Several years ago we
> > were forced to find a way to reduce the number of MODS accesses to
> the
> > W3C server. The reason was that W3C was complaining (loudly) about
> > excessive accesses and threatening to block certain clients. Someone
> > was not properly caching xml.xsd and was in addition validating an
> > inordinate number of MODS records.  This happened a number of times,
> > we were unsuccessful at tracking down the culprit, and as a quick fix
> > changed the reference to LC rather than W3C, and the problem has not
> resurfaced.
> >
> > Xlink is more complicated, although you could use the same
> > justification, even if there weren't additional complications. In the
> > Xlink case, the W3C version simply didn't meet MODS requirements.  I
> > can't recall exactly why, I'm tracking that down, and I'll get back
> to
> > you (but I wanted to respond quickly to the question).
> >
> > --Ray
> >
> >> -----Original Message-----
> >> From: Metadata Object Description Schema List
> >> [mailto:[log in to unmask]] On Behalf Of Wolfgang Koller
> >> Sent: Monday, March 21, 2011 4:53 AM
> >> To: [log in to unmask]
> >> Subject: [MODS] Problems with Import(s)
> >>
> >> Dear all,
> >>
> >> I'm currently working on a schema which uses MODS to track the
> >> bibliographic information of an element.
> >> However, unfortunately, there are several critical imports in MODS
> >> which heavily conflict with other schema which try to import into
> the
> >> same namespace (multiple definitions of the same attributes /
> elements).
> >>
> >> Unfortunately MODS uses its own copy of the xml.xsd schema and the
> >> xlink.xsd schema.
> >>
> >> - As far as I found out, the xlink schema is a separate & modified
> >> version of the original xlink schema which can be found at
> >> http://www.w3.org/1999/xlink.xsd. However from my point of view, it
> >> is heavily dangerous to customize a schema but import it into the
> >> same namespace then. I would recommend defining a own namespace for
> >> your custom schemas (even if they are based on an "official" schema).
> >>
> >> - The same applies for the xml.xsd schema (the official version can
> >> be found at http://www.w3.org/2001/xml.xsd). However there I did not
> >> find any difference in the official and the version hosted by loc -
> >> what's the reason for hosting it own your own?
> >>
> >> Is there any chance that you are going to update mods and reference
> >> the official schemas and/or change the target namespace so that mods
> >> can be combined with others schemas trying to import the official
> ones?
> >>
> >> Best wishes,
> >> Wolfgang
> >>
> >> --------------------------------------
> >> Information gemaess UGB Par. 14 Abs. 1
> >>
> >> Naturhistorisches Museum
> >> 1010 Wien, Burgring 7
> >> Firmenbuchnummer: FN 236724z
> >> Firmenbuchgericht: Handelsgericht Wien
> >> UID: ATU 38020609
> >> Rechtsform: Wissenschaftliche Anstalt oeffentlichen Rechts des
> Bundes
> >> --------------------------------------
> 
> --------------------------------------
> Information gemaess UGB Par. 14 Abs. 1
> 
> Naturhistorisches Museum
> 1010 Wien, Burgring 7
> Firmenbuchnummer: FN 236724z
> Firmenbuchgericht: Handelsgericht Wien
> UID: ATU 38020609
> Rechtsform: Wissenschaftliche Anstalt
> oeffentlichen Rechts des Bundes
> --------------------------------------