Hi
Good question.
The ISAD(G) defines Existence and location of copies as:
Purpose:
To indicate the existence, location and availability of copies of the unit of description.
Rule:
If the copy of the unit of description is available (either in the institution or elsewhere) record its location, together with any significant control numbers.
and the Examples:
Digital reproductions of the Christie family Civil War correspondence are available electronically at
http://www.mnhs.org/collections/christie.html. (Fonds)
U.S., Minnesota Historical Society
In August 1988 a photocopy of item 81645 (from the Japanese War Crimes Trials section of the series)
was transferred to the Australian Archives from the Australian War Memorial under the number
1010/6/134 and accessioned into series A2663. (Series)
National Archives of Australia
The Mabo Papers have been microfilmed onto 11 reels of 35mm film held at NLA Mfm G 27,539-
27,549. Full sets of the microfilm are held by the Townsville and Cairns campus libraries of the James
Cook University of North Queensland. (Fonds)
National Library of Australia
Cases numbers 1-769 have been reproduced as National Archives and Records Administration microfilm
publication M1082, entitled “Records of the U. S. District Court for the Eastern District of Louisiana,
1806-1814.” (Series)
U.S. National Archives & Records Administration
Les cahiers de doléances ont été microfilmés sous la cote 2 Mi 30 (File)
Direction des archives de France
Una copia dei microfilm e delle trascrizioni furono depositati nel maggio 1941 nella Widener Library di
Harvard (Cambridge, Mass) e si trovano ora nella Houghton Library (*48M-394) (Series)
Italy, Istituto Storico della Resistenza in Toscana
Microfilmes 045-97 a 054-97. (Fonds)
Brazil, Arquivo Nacional
As you can see, the standard defines a "mix of things" as free text, a URI, a description, a code, a place, and so on, all in one place. In my opinion, this approach is a weak strategy that prime the simplicity (every ISAD(G) archive can import free text in from other archive without complicated rules) beyond the quality of data as you mentioned (free text vs structure), that is reason why we cannot define a structure of relationships with a well defined concepts with this definition.
Is it possible to extend the ISAD(G)? Yes, Dédalo can do it, but we will be deviating from the standard, and this modelling extension will be incompatible with current archives.
Therefore, your proposal could be acceptable, but it's outside the standard. If the community agrees on it, I can implement it. If not, you can extend the ontology with your local TLD.
Please, include some other people from other archives to the discussion.
@MercePB , @Eulàlia Mesalles , @Conchi
Best
