One of our esteemed clients pointed us to this announcement from NLM:

https://www.nlm.nih.gov/pubs/techbull/so15/so15_cataloging_unstringing_subject_heading.html

In essence, NLM is proposing to change the way their MeSH authorities are constructed, which has far-reaching repercussions for our Backstage clients that currently receive MeSH authorities. This change is set to take place in January 2016.

NLM is re-formatting their headings in a faceted approach, very similar to how OCLC’s FAST authority database treats its own headings (which are based on LC subject headings).

For instance, this single MeSH authority would transform from:

150 22 $a Cross Cultural Comparison $z Africa $v Congresses

To these separate MeSH authorities:

150 22 $a Cross Cultural Comparison

151 #2 $a Africa $x ethnology

155 #2 $a Congresses

The consequence of this change means that Backstage will no longer be able to match your headings against a MeSH authority database in the manner you have been doing up to this point. If we attempt to match headings which resemble the first example above, we would only hit on the first “Cross Cultural Comparison” MeSH authority as a partial match; essentially considering the rest of the subdivisions to be free-floating (and un-match-able at that point).

This also means that your existing MeSH authorities with the full strings in our copy of your authmaster will update from the full authority to just one of the faceted headings. Clearly this is not the desired result, so we are working on methods to ensure that your data is transformed to fall in line with the changes being made at the National Library of Medicine.

At Backstage, we could propose to try to convert your existing MeSH headings over to the new faceted format ahead of the change in January 2016. There would likely be some cost associated with this service and we would prefer to start exploring this as soon as possible in light of the approaching deadline.

The challenge we face is determining how MeSH authorities will be faceted. The information we have from NLM right now is that headings may convert from full strings to 1 or 2 subfield headings. We are working on a way to facet bibliographic headings to match the faceting scheme being used by NLM, though we do not yet have a solution in place.

To tackle the complexities that our Authority Notification process (which houses your MeSH authorities and periodically checks for updates) introduces, we are leaning towards purging the MeSH authorities from your master authority file (at your request, of course). Then, we would take all of your records which have MeSH headings, perform the conversion (when available), and add those corresponding authorities from NLM into your master file.

Then, with the Current Cataloging service (which processes your new/acquired bibs since the last time we did your processing), we would propose to apply the conversion to all MeSH headings such that we remain consistent in how those are treated going forward.

We welcome your feedback as you consider this information.