I think there may be a useful distinction to be made between these two cases which match Rich's most recent cases 1 and 2+3):
- A jar of mixed semi-identified organisms
from known-to-be disjunct taxa (e.g. two molluscan genera, a green alga, and some fish larvae).
- A jar of one or more organisms collectively
identified down to a single taxon of any rank (e.g. a jar full of ophiuroids only, all of which may or may not be the same species, but they're all "known" to be ophiuroids).
That wasn't exactly the distinction I was making. I started writing a separate post on this issue, but only got about half-way through before I discovered that I wasn't even sure what my own point was, so I shelved it for a later time.
What concerns me, though, is that you're still effectively introducing "rank-ism" in the distinction above; as if a set of mollusks, alga and fish were somehow fundamentally different from a set of organisms from seven different families of ophiuroids.
My proposed solution is to rigidly maintain that an instance of "Individual" can not be partitioned to have multiple separate but concurrently legitimate Identifications associated with it. It can have multiple Identifications, but they would be considered to either be competing with each other (when different taxa are asserted) or reinforing each other (when the same taxon is asserted). They would *not* be considered concurrent with each other, and applying to separate "parts" or "members" of a single aggregated Individual instance.
When, we know what the taxonomic breakdown is with some additional precision, we partition out "child" individuals down to the level at which we are able to confidnetly discern distinct taxa (and have time/resources to attach Identifications as such). That way, we keep our basic agreement that an Individual must represent an aggregate of the same taxon, but we don't impose any rank limitiations to what that taxon might be.
So, in your example, we would have one instance of Individual representing the whole jar (assuming we wanted such an instance to record the fact that they're in the same jar, or whatever. That Instance may have no Identification instances associated with it, or maybe only one for "Eukarya". But if you wanted to acknowledge the specific representations of mollusks, algae, and fihses, you would generate (at least) three "child" Individual instances, derived from the one "parent", and then each of those child instances would have its appropriate taxon Identification attached.
Without (yet) wrapping my head around this entirely, I think I agree with Rich that we definitely find it useful to be able to search taxonomically for higher level taxa as well as searching for species. Without being able to do so, we are forced to ignore all instances that are not identified to species, and that's just not a happy solution.
It's a little more subtle than that. As Steve pointed out early on (in his response to John), we can still leave an organism identified only to the level of, say, Order or Family; but still "believe" (confidently?) that when we do make a more careful determination, we will find only a single species among that aggregate.
The real question is: when we *don't* know (with confidence?) that the constituents of an aggregated "Individual" will ultimately be shown to represent a single taxon at the rank of species (or lower) -- or going even further, when we *already know* that more than one species-rank taxon is likely to be involved -- we should not be discouraged from treating the aggregate as a single instance of an Individual, with a single legitimate Taxon Identification, at whatever rank (Animalia, Ophiuroida, whatever) -- IF and WHEN circumstances warrant it. At the moment, the only such circumstances for the latter sort (i.e., we know that more than one species-level is probably involved) that I can imagine are when we have material, but we do not have the time/staff/expertise/whatever to go through and add more taxonomic precision to the Identification(s).
I've made the claim that we sometimes find it interesting to be able to search taxonomically for (actually, to find) records that describe the mixed-taxon case #1 above. However, without allowing a one-to-many relationship between "Individual" and a determination, I don't see how to accomodate it in a straightforward scheme, and nor do I think it is necessarily a good idea to do so.
That was buried in my last big post on this. I agree that it's not a good idea to do so. The solution is, when you are aware of what the subgroups are, you generate instances of "Individual" to represent each one, then attach an appropriate Identification to each. You can still keep them in the same jar; it's just that your database knows that the "parent" Individual instance (the whole jar) has no Identifications associated with it, or maybe only "Eukarya" or "Animalia" associated with it; and further that this one "parent" Individual has multiple (semantically linked) "derived" (or "child") Individuals, each of which has a more precise taxon Identification.
Unless a simple solution presents itself to me, I'm willing to accept the idea that my case #1 and case #2 cannot be folded into one tidy model.
I think the solution I proposed in my earlier email is sufficiently simple in all respects *except* in terms of trying to explain it using the English Language rendered in ASCII.
When I get time, maybe I'll whip up some diagrams and a better articulation of what I mean. But first, read my earlier post and see if I managed to explain it just coherently enough....
Thanks,
Rich