Dear Ed, dear all,
this is interesting, and from my perspective a good use case -- with no official MARC solution available (at least not yet).
We have similar data in the Integrated Authority File (Gemeinsame Normdatei, GND). We call it "zeitliche Gueltigkeit", or chronological validity of a relationship. Some relationships (approx. 100,000 in 64,000 records) are qualified by chronological information, because the relationship is not valid indefinitely, but on a limited range of time. This comprises years, exact dates, or textual information, either single ones or open or closed time spans.
Internally the information is cataloged and stored in a subfield $Z (mnemotechnically, the "Z" is the first letter of the German word "Zeit", menaing "time"). Up to now in MARC it is given as a "local" subfield $9 with a "sublabel" "Z", followed by a colon ":".
For example, the record describing Stefan Zweig
has some 551 fields with a $Z / $9Z:
024 7# $ahttp://d-nb.info/gnd/118637479
100 1# $aZweig, Stefan$d1881-1942
So Great Britain and the USA and Brasil were stations of his exile, during the years given in the respective fields.
The information is bound to one specific field, and given the lack of free subfield codes, I don't see an easy MARC solution (other than the local subfield $9).
Let me mention that in fall 2015 I have drafted a Discussion Paper for the MARC Advisory Committee, covering field-bound information, among them chronological validity of a relationship, and language and script of a MARC field content. After some internal discussion we decided to withdraw the paper.
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*** Reading. Listening. Understanding. German National Library ***
Date: Fri, 24 Mar 2017 15:03:51 -0800
From: "Ed M. Kazzimir" <[log in to unmask]>
Subject: A plan for defining 'start' and 'end' periods for "See also" tracings?
Is there any plan to define a subfield in 5xx fields in authority records to indicate the time period when the relationship was valid?
I have this situation (which I often encounter in my work), where multiple fields of the same relationship appear in one record:
510 2 ǂi Hierarchical superior: ǂa National Science Foundation (U.S.) ǂw r
[true from January 28, 1985 to July 22, 2010]
510 2 ǂi Hierarchical superior: ǂa National Science and Technology Council (U.S.) ǂw r
[true since July 22, 2010]
I wish it were possible to use "ǂs 1985 ǂt 2010" (but, of course, ǂs and ǂt already represent other data elements). I wish inputting exact dates were possible, as I think I have seen agencies change organization twice in a year, and definitely I have seen year-to-year changes.
If these fields display (especially to the public), it would be very desirable to indicate which body was superior at which time. As it is now without qualification, it looks confusing to me or looks like the record creator got two similar names mixed up (non-technical service staff do not see 670 fields).
It is possible that multiple hierarchical superior bodies are concurrent or overlap partially in time, so without being able to qualify by dates the situation as presented now looks ambiguous. And it would be helpful to qualify by date for all other types of 5XX relationships.