[tdwg-content] DwC formal semantics, was Re: dwc:associatedOccurrences

[Bob Morris]

On Tue, Aug 24, 2010 at 9:14 PM, Steve Baskauf
<steve.baskauf at vanderbilt.edu> wrote:
> As I was stuck in traffic this morning I was thinking about my response to
> Bob's comments.  In retrospect, I should have simply said that indicating
> that specimens are duplicates by assigning their dwc:individualID property
> to the same URI is really not just one option, but rather that it is the
> semantically correct thing to do.

If "semantically correct" is meant to be something about formal
semantics, I  am not yet prepared to believe that the DwC rdf profile
is amenable to useful OWL formal semantics as it stands. (It also
makes no claims to do so, and for reasons I'm sympathetic to, probably
shouldn't). A little about this later.

> [... stuff about owl:sameAs and whale sharks]

The paper by Halpin and Hays  [1] shows that even for Linked Data,
owl:sameAs is more complicated than may seem. (The paper also asserts
that not much reasoning is presently done on Linked Data, so I suppose
any particular use of owl:sameAs for anything but machine reasoning
may in practice be harmless for present Linked Data tools.)

My  understanding from studying it is that dwcterms.rdf makes no
pretense to be an OWL ontology, nor do its authors claim that.  It
uses rdf and rdfs with close to no formal semantics restrictions. Put
another way,  it is about as open world as it could get and still be
valid rdf.  Although I at  first was annoyed by this(*), I have come
to believe that it is probably a boon, because it allows multiple
profiles to be built on dwcterms.rdf, using it as controlled
vocabulary but allowing formal semantics to be determined by the
axioms of the profile. I agree with your opinion "it is wrong to
invent some other term to represent a relationship that can be clearly
and unambiguously expressed using existing terms", but formal
semantics imposes a definition of "unambiguously expressed" and
practitioners of one domain may accept a particular unambiguous
expression,  while those in another don't. Information systems have to
be accepted, not merely unambiguous.  After I've tried to build a few
DwC OWL profiles for distinguishable communities of collections
practice, I'll look again at your arguments to see how much
commonality I (and more importantly, my informants) think there is
lurking in the profiles.

I expect that some of these kinds of issues will be on the table at
several of the proposed Wednesday/Thursday sessions at TDWG. Hope
you're there.


(*)A good example is this:  wrestle dwcterms.rdf into Protege 4 and
then go looking for dwc:basisOfRecord. You won't find it listed as a
Property, and unless you understand the whole rdf stack, you'll be
mystified why Protege is merely unhelpful, not broken, in this case.

Bob

[1] "When owl:sameAs isn’t the Same: An Analysis of Identity
Links on the Semantic Web", Harry Halpin and  Patrick J. Hayes
http://events.linkeddata.org/ldow2010/papers/ldow2010_paper09.pdf
-- 
Robert A. Morris
Emeritus Professor  of Computer Science
UMASS-Boston
100 Morrissey Blvd
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Associate, Harvard University Herbaria
email: morris.bob at gmail.com
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