"population" or "taxon" -- things get very messy. During the previous discussion, it seemed that everyone agreed that "taxon" was too broad and not useful for our purposes; whereas "colony", "school", "herd", etc. were absolutely necessary (lest we need to treat every polyp on a coral head as a separate database entry, and many use cases involve treating herd/pod/flock as an important unit to be able to track in exactly the same way that "individuals" are tracked -- which is why the definition of dwc:individualID is as it is). The border-line term is "population" -- which is cleary below the realm of taxon, but perhaps a bit too vauge and poorly defined to be regarded as the same class as an individual.
Yes, and I am also thinking of metapopulations, just for fun...
I understand that we need an operationally defined term with a particular use case. Primarily I agree with Chucks observation that an important point is that we believe to understand what an individual is, both in biology and in informatics and philosophy, so I just want to warn about the use of this. Secondarily I do believe we need to define it in a way that the upper limit of the set we want to refer to becomes clear, at least operationally. I was missing that.
WIth respect to the operational usefullness of a term that does not distinguish between part, individual, set of taxonomical homogeneous OR heterogeneous samples (you excluded tax. heterogeneous, which would exclude lichens, most plants (mycorrhiza!) or any other symbiosis like us humans with our skin and intestine microbes) I have two proposals:
Broadly the term "sample" implies not necessarily physical sampling, you can sample observations or data. A sample is a subset of a (statistical) population, selected under operational rules and encompasses the individual and part. Think of sampling music.
The other term is unit. What you describe has been discussed extensively in the CDEFG and later ABCD papers and standard and the term "Unit" was chosen for as far as I understand exactly the concept you are looking for. Perhaps that can be followed, if we accept that these are not "natural" units, but operationally defined units (think of OTU, oper. tax. units). Unit was chosen in ABCD because it applies both in a sampling context, in an analysis context, and in a collection curation context.
Apologies should I repeat something already discussed previously.
Gregor