[tdwg-tag] "Class" attribute in DwC [SEC=UNCLASSIFIED]

Richard Pyle deepreef at bishopmuseum.org
Tue Aug 18 08:45:48 CEST 2015

A few quick comments:

> In which case, you would need a separate class for a thing that happens at
> time, but which is not located (and perhaps, as the philosophers say, does
> not have an extension).

Not necessarily; at least not from the perspective of modelling biodiversity
data.  If you really wanted to capture a load of metadata about the "time"
aspect (which one could actually do), I could see justification in
establishing a class of object for the "Time" component, in the same way
that we have a class for "Location".  But fundamentally, we're just talking
about coordinates for four-dimentional space-time; so really "Location" and
"Time" might best be wrapped into the same "Space-Time" class (i.e., the
"Where/When" class), and the Event would then become something along the
lines of a "Who/What" class.  But at some point, perfecting the conceptual
data model represents an impediment to practical progress.

> And this in a way is a reply to Bob's original question - why aren't these
> relationships explicit? The reason is that the second you try to make them
> you almost immediately start running into philosophical conundrums that
> people have been debating for thousands of years. The old "How many
> angels can dance on the head of a pin?" problem is an exercise in
> distinguishing between things that are located and things that are

Agreed!  The art all of this is in balancing the "Normalize until it hurts"
exercise, with the "De-Normalize until it works" reality.  There's no
objectively correct answer.  Just a cloud of possible options that we're
gradually trying to collectively sharpen down.

> Something as abstract and basic as "thing that happens at a place and a
> time" should be borrowed from someone else's vocabulary.  The first
> problem there is that if you do that, then if that other vocabulary
> inference rules, then anyone that uses your vocabulary must respect those
> rules or their ontology becomes inconsistent.
> Another problem is that other people's vocabularies are never really quite
> exactly what you need.

DEFINITELY agreed!!!!

> And the underlying problem is that something as simple as "a point in
time" is
> actually a really hard question. What about things that have a duration,
> happen over a couple of weeks? Things that are cyclic?

Indeed!  And it was a poor choice of words on my side to use the word
"point".  "Time" should be regarded in the same way that we regard the other
three dimensions. That is, either in the form of an arbitrarily precise
point with an explicitly stated error (as we do in DwC for geocoordinates),
or in an explicit min/max range (as we do in DwC for things like elevation
and depth), or in a way that handles real-world data (actual ranges, ranges
representing imprecision/uncertainty, and multiple points within a scope
bound by min and max values, etc.)  We could deal with this stuff by
treating "time" as a class, but in my experience (and yes, I actually did go
down that road many years ago), the payoff ain't worth the investment.

> So is there any hope at all that we can create a distributed semantic web
> facts relating to taxonomy - the output of the taxonomic work that people
> are doing)?

Probably not.  At least not in my lifetime (or career-time).  But one can
always hope! :-)

> I think so, because the biologists and taxonomists are working on the same
> stuff, certainly the same kinds of stuff, within the constraints of the
> WorldT. And this maybe is a clue about where to look for useful
> Rather than attempting to solve age-old questions about the nature of time
> and thing, look to the specific subject matter.

Yeah....but.... we can't even get past the tired old arguments about "what
is a species", and the difference between nomenclature and taxonomy (names
and concepts), and even the word "name" has a staggering heterogeny of
meanting even within the confines of biological nomenclature/taxonomy.  It
baffles me that the same arguments that were going on when Taxacom/TDWG were
born, continue almost unabated today.  But, like I said.... one can always
hope! :-)

> After all - why have an 'event' class at all? The only thing you can do
> such a class is to construct a query that asks, for instance, "tell me
> everything whose foaf:person is Dr Joe Bloggs and that is a thing that
> happened".  On the other hand, "specimen" in the strict sense of
> in a collection with an accession number" is very important, fairly
specific to
> the subject matter, and entirely worth having a common term for.

We've debated this one back and forth as well.  But it always ends up in the
same place.  That is, all of these arguments ultimately end up with the same
conclusion: everything should be reduced to a triple-store.  Indeed, life
would be so easy if that were actually practical. At this stage of human
digestion of biodiversity data, software availability and consumer fluency,
and a number of other Real WorldT issues, however, it does not seem to be
the path of least resistance towards progress.

> Likewise, 'location' may mean 'geographic polygon', or it may conceivably
> mean a collection, or an institution. (How so? Because a location is
> that might be given in reply to the question 'where is X?'. Notice that
this is
> language-dependent). Each of these three things has an existing vocabulary
> defined by geographers, librarians, and (I suppose) company registrars
> respectively. Does anyone really need a higer-layer linking them together?

And this is trivial compared to the analogous issues surrounding the  term
"taxon" (or "taxon name", or "taxon concept", etc.)  Oy vey!

> Enough rambling, I think. FWIW:



P.S. Bob -- yes, I transcribed both posts to GitHub....

Richard L. Pyle, PhD
Database Coordinator for Natural Sciences | Associate Zoologist in
Ichthyology | Dive Safety Officer
Department of Natural Sciences, Bishop Museum, 1525 Bernice St., Honolulu,
HI 96817
Ph: (808)848-4115, Fax: (808)847-8252 email: deepreef at bishopmuseum.org

More information about the tdwg-tag mailing list