Hi Peter and Donald,

Peter: Thank you for that excellent and cogent description. I found myself nodding my head in agreement at essentially every point you made. In particular, this passage captured exactly what I hoped to express (but perhaps failed) in earlier posts:

And of course it should be a major concern to make the mapping between unique identifiers assigned to entities a 1:1 relationship

as

much as possible, by making the mapping algorithms as intelligent as

possible.

But again maintaining a 1:1 relationship only exists in the perfect world

(even

if there is only one authority that can assign new identifiers) and we

should

thus come up with schemes that work in practice, as the one descibed

above.

Donald:

I think that in practice the potential taxon sensu Berendsohn (1995) is precisely what TDWG has primarily been addressing in recent discussion of taxon concepts. TCS can accommodate expression of other mechanisms for defining taxon concepts but does not (at least yet) do much to allow us to reason about them.

I agree that we should be aiming to create tools that wherever possible

can

give us an assessment of which taxon potential taxa cluster closely enough that we can treat them as a 'granule'. That is a further challenge and

one

that will probably largely depend on what sort of information taxonomists and others are really prepared to put into a standard like TCS.

I agree completely. If we can agree that taxon name units can be objectively (for the most part) defined(*), and that "documentation" units (publications, references, whatever) can be objectively (for the most part) defined(*), then I think we automatically have a mechanism to uniquely identify name-usage instances that can be objectively (for the most part) defined. Rather than get bogged down in trying to come up with a satisfactory "semi-objective" definition of which name-usage instances rise to the level of potential taxa, or full-blown "taxon concepts", I think we're better-off hard-indexing the raw name-usage instances and secondarily applying algorithms that allow "clusters" of these name-usages to emerge as potential or likely concept "granules". The relevant question in this context is whether "Taxon Concepts" represent their own distinct data domain worthy of a dedicated GUID system, or not. My hope is that someone on this list who believes that concepts can (and should) be defined separately from clusters of name-usage instances, and receive their own GUID as such (separate from names), will outline that perspective.

(*)=Exactly how each of these two things is defined remains an open question, but the point is that whatever definition we end up with, it will likely be one incorporating very minimal subjectivity.

Aloha, Rich