Let me attempt to answer with an example (apologies if I digress with content better related to other topics):
INBio (Costa Rica) had an Institutional Collection but the Research Department (Inventario) would probably clarify that it was actually several collections (Plantae, Insecta, Fungi, Mollusca, Nematoda, Arachnida, Myriapoda, Onychophora). Now Collection Managers (Curators) would argue there were different Collections (“Dry” Mounted Duplicates, Seeds, “Xyla”, Wet, Vouchers Collections and so on) and each had its own protocols and management methods.
For example, a specialist could visit and take specimens of her group from the wet collection (of Malaise traps’ soups) of insects, mount them and identified them for the dry collection. Some times, duplicates from a single collecting event would be sent to other institutions. Other times, live specimens will be grown in-house and by-products of the process would be catalogued as vouchers of Natural History associated to the specimen, the plant it fed from would go to one collection, the final dead specimen would go to the dry-mounted collection, next to all of its by-products.
Counting number of specimens was dependant on the definition of specimen itself that each Collection Manager decided (the mollusks in 1 rock, the shells in a vial, the sheets from the same plant, the nematodes mounted in one plate). Sometimes they will count each of them separately, sometimes they would count all of them together as one. It didn’t matter what each collection considered an specimen, numbers were provided for the annual account and the reports to donors. In some cases, while digitization was still going on (not finished yet), an estimation was made using the same sampling method every year and the totals kept growing until, finally, the year the backlog digitization caught up, the total (not-estimated) number of specimens diminished considerably for some of the collections. Much later, INBio gave their collections away to another institution that finally incorporated them with their own collections.
Summarizing,
- There is a hierarchy in Collections that has to be reflected in the data handling.
- Collections will definitely overlap (thinking Dimensions in TDWG CD Standard here).
- A Collection could be housed in different Buildings/Departments but we are tending to an Institution-based model. So CollectionA[OneHalf@InstitutionX] is a different Collection than CollectionA[OtherHalf@InstitutionY] and a Collector’s life-long collecting events (one possible dimension?) will also be divided by (Hosting) Institution, too.
- Depending on the Managers’ definition of their Collections, a collecting event could produce specimens in different Collections.
- Total numbers estimated and reported by Collection Managers should maintain the calculation methods consistent throughout reports. Therefore, estimation method might be something to consider stating in the metadata (and maybe considering defining a categorization/vocabulary for it?)