Kevin Richards wrote:
I'm not sure I agrre here...
Steve Baskauf [steve.baskauf@vanderbilt.edu]
Unfortunately, this issue has been clouded somewhat by
adoption of the term Occurrence for the class that includes specimens
and observations. I understand the reason why this was done (i.e.
because specimens and observations both can serve as records of
occurrence), but I think it would be better to have used something like
"DerivativeResource" (i.e. a resource that is derived from an organism)
for the dwc:recordClass rather than "Occurrence" because an occurrence
can documented by resources other than specimens and observations
I think there is really only 2 categories of occurrence here - those with physical vouchered specimens, and those with digital only representations. Only those with a physical specimen are "specimen occurrences", all others are "observed occurrences" (even if thay have an image assocuated with them).
The distinction I was drawing was between non-physical resources that
return a representation of the organism and those that do not. For
example, a database record representing a digital image of a bird could
contain a URL to the location from which the bird image can be
retrieved. A consuming application could retrieve this file and
display it on the screen for the user to see. In contrast, a database
record representing a checked box for a Christmas Bird Count
observation the same bird can
return no representation of the bird. Both records would have the same
metadata about location, date, taxonomy, observer, etc. but only the
former would have metadata of the sort that MRTG is dealing with
(copyright and licensing information for the image, a title, caption,
etc.). In a third case where a bird was mist-netted and the wing
length
measured, one could put the record in either the first category or the
second depending on whether one considered the wing length to be data
or metadata. But that is a question for the observation people and out
of my area. My point was that aside from occurrences with physical
vouchers, there are two fundamentally different types of resources:
those that return a digital representation of the organism and those
that don't. If a record is linked to a digital representation
(StillImage, MovingImage, or Sound), a user may examine that
representations for physical or behavioral characters that would allow
the taxonomic determination of the organism to be verified, while in
the checklist example, the user would simply have to trust the
identification ability of the observer.
I can't see why this would really restrict you from represetning any occurrence data you may have.
Also, one of the beneficial things about DwC is its simplicity and specificity. If we generalise again (to handle "all" types of occurrence, "resources derived from organisms"), then I feel the ontology will become less usable, and obvious, to end users. Sometimes it is a good thing to specify precise data fields and types in an ontology.
My problem here is with use of the word "occurrence". The nature of
that word implies that the record represents a valid occurrence record
for a species, i.e. that the record could appropriately be used to put
a dot on on a distribution map for the species. If I take a StillImage
of an Osmorhiza longistylis plant in the woods and my digital
camera records the time and GPS coordinates, then those metadata
indicate that Osmorhiza longistylis occurred in that woods on
the day that I took the image. On the other hand, if I take an image
of a PreservedSpecimen of Osmorhiza longistylis in an herbarium
and my camera records the same information, it would not be appropriate
to use those time and location metadata to put a dot on the Osmorhiza
longistylis distribution map at the location of the herbarium.
Rather, the time and location metadata for the collection of the
PreservedSpecimen should be used to place the dot. I still need to
record the time and place where the specimen image was taken, I just
don't want for it to represent an occurrence. That is why it bothers
me to classify a StillImage of a PreservedSpecimen as a recordType=Occurrence.
My suggestion of the term "DerivativeResource" was an attempt to
divorce the USE of the image (to document a valid occurrence or not)
from what the thing IS (a representation that was derived directly or
indirectly from an organism). Calling such representations something
other than "Occurrence" gets us away from the issue raised by Gregor
and Bob where there are many possible uses for a resource. When I take
live plant images, I consciously intend for them to be used
simultaneously to record an occurrence, illustrate characters, and be
used for media tools such as visual keys and visual recognition
software, not just to document an occurrence.
I should also note that although this problem is widespread for images,
it can also apply to physical resources as well. A PreservedSpecimen
taken from a wild-collected plant growing in a botanical garden or
animal in a zoo (i.e. from a LivingSpecimen) has the same problem.
Both would provide useful information for identifying the organism but
in neither case would the PreservedSpecimen collection time and
location represent a valid occurrence that should used to put a dot on
a map. The collection time and location for the LivingSpecimen would
be the metadata to use to place the dot (i.e. valid occurrence).
Because DwC has traditionally been applied primarily to preserved
specimens which usually represent valid species occurrences, this may
not have been a very important issue, but for people like me who want
to apply DwC to images it is a big deal.
Steve Baskauf
--
Steven J. Baskauf, Ph.D., Senior Lecturer
Vanderbilt University Dept. of Biological Sciences
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