[tdwg-content] Conflict between DarwinCore and DublinCore usageof dcterms:type / basisOfRecord

Steve Baskauf steve.baskauf at vanderbilt.edu
Sun Oct 25 12:59:32 CET 2009

Kevin Richards wrote:
> I'm not sure I agrre here...
>>> Steve Baskauf [steve.baskauf at 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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