Joachim,

Using xlink:href as you describe is considered the proper way in MODS to reference an authority. A related example is in the MARC 21 to MODS mapping (http://www.loc.gov/standards/mods/mods-mapping.html), which shows that subfield 0 (zero) in MARC 21 is equivalent to use of the xlink attribute in MODS.

However, xlink can be used in a MODS record for a variety of external linking purposes, some of them having nothing to do with authority records or authority URIs. That seems to me to present problems for processing a MODS record. I wonder if MODS users will find they want a more specific attribute defined that can only contain an authority URI. So, I'm not convinced that use of xlink is the best practice in the long term for encoding a link to an authority URI. I will raise this issue with the MODS/MADS Editorial Committee.

Joe Altimus
Arizona State University Libraries

On Thu, Feb 19, 2009 at 1:51 AM, Neubert Joachim <[log in to unmask]> wrote:
We are mapping data to MODS record structures (from a PICA library system via Marc21 interface) . This includes various kind of authority data, eg. subjects, persons etc. For subjects, the authority data is in SKOS. (Thesaurus for Economics, preview on http://www.zbw.eu/beta/stw). It is based on concepts with an URI as persistent identifier. The concepts have prefered labels in German and English, which should be present in the MODS records for display and indexing convenience.
 
What we figured out as a possible solution is this:
 
<subject authority="stw" xlink:href="http://zbw.eu/stw/descriptor/19664-4" lang="en">
  <topic>Financial crisis</topic>
</subject>
<subject authority="stw" xlink:href="http://zbw.eu/stw/descriptor/19664-4" lang="de">
  <topic>Finanzmarktkrise</topic>
</subject>
 
(We don't really like the de-normalized form. Much better would be:
<subject authority="stw" xlink:href="http://zbw.eu/stw/descriptor/19664-4">
  <topic lang="en">Financial crisis</topic>
  <topic lang="de">Finanzmarktkrise</topic>
</subject>
However, that's invalid in MODS 3.3)
 
What do you think - is it ok to use xlink:href for the reference to the authority record?
 
Since we are new in the MODS field, we wonder if there is are other solutions or best practices for this we may not be aware of.
 
Cheers, Joachim
--
Joachim Neubert
IT Development
German National Library of Economics (ZBW)