[tdwg-content] DwC Occurrence [SEC=UNCLASSIFIED]

[Peter DeVries]

Hi Paul,

One problem with the type system and many species descriptions is that they
don't provide much insight or guidance as to where one species ends and the
other begins.

We need some system of documented concepts that makes the process of
matching an individual to a concept clearer and more repeatable.

So that someone can determine the *most appropriate* concept for their
individual.

It should also be designed so there is high repeatability across different
expert identifiers. (Same specimens matched to the same concepts with high
repeatability)

- Pete

On Tue, May 31, 2011 at 10:09 PM, Paul Murray <pmurray at anbg.gov.au> wrote:

>
> On 31/05/2011, at 9:10 PM, Nico Cellinese wrote:
>
> What I don't seem to be able to digest is the notion that same individual
> will later be equaled  by some to a species. That assertion is hard to
> swallow.
>
>
> Is this do do with type specimens? Or are we talking about the OWL class
> vs. OWL individual problem?
>
> With respect to taxa, it seems to me that a taxon is a rule that can decide
> whether or not an individual is part of the taxon or not. This can be done
> with a description, by specifying a list of included and excluded other
> taxa, or by various other ways. If two taxa defined differently select the
> same subset of real-world individuals, then the taxa are synonymous. This is
> to say: the truth of assertions about taxonomic relationships can be
> contingent on what is out there in the real world.
>
> (The taxa "organisms that have the front half of a horse" and "organisms
> that have the back half of a horse" would be synonymous if not for the
> occasional zebra/horse hybrid. Actually ... this is a stickier point than it
> seems: is a taxon a subset of all potential individuals, or a subset of all
> actual individuals? Or a subset of all actual individuals ... including the
> ones that aren't currently alive, and that we don't happen to know about? Is
> a taxon the *rule*, or is it the *subset* of individuals? Is the rule - the
> definition or circumscription of the taxon - the "taxon concept", and the
> actual subset of individuals the "taxon"?)
>
> Anyway - to return to "species = individual":
>
> Since a taxon is simply some rule for selecting individuals out of the set
> of all individuals, you could quite happily define a taxon "the set of all
> individuals whose tokens are the type specimens of *Vombatus ursinus*".
> This is not the same as the species, or the nominal concept - it's a
> "concept" containing one individual. I suppose it might be called the "type
> taxon" of a name.
>
> Interestingly, this taxon of one individual is not an entirely useless
> idea. All taxa that are named "V*ombatus ursinus"* by definition contain
> the type taxon as a subset (except in cases of misattribution). From this,
> and the rule "if two taxa have a common nonempty subtaxon then they
> overlap", we can infer "if two taxa have the same (not misattributed) name,
> then they overlap". This is not something that could otherwise be inferred,
> because in general "a overlaps b" and "b overlaps c" does *not* allow us in
> infer "a overlaps c". It's the existence of the common subtaxon - the type
> taxon - that does. It's the existence of this overlap - even of just one
> individual - that gives meaning to different authors using the same name to
> label their concepts.
>
> (I am not sure that I am not repeating myself - I may have brought this up
> on this list previously)
>
>
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-- 
------------------------------------------------------------------------------------
Pete DeVries
Department of Entomology
University of Wisconsin - Madison
445 Russell Laboratories
1630 Linden Drive
Madison, WI 53706
Email: pdevries at wisc.edu
TaxonConcept <http://www.taxonconcept.org/>  &
GeoSpecies<http://about.geospecies.org/> Knowledge
Bases
A Semantic Web, Linked Open Data <http://linkeddata.org/>  Project
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