It sounds like perhaps now is the time to focus on the ontological relationships among classes, as the next major focus of DwC advancement.
I would NOT regard "HumanObservaton" as a subclass of "Event". I believe that "Event" should be kept clean as fundamentally an intersection between a Location instance and a point in time. After much thinking and testing on this, we've finally come to the conclusion in our data models that "Location" is defined by two of the four space-time dimensions (X & Y; effectively represented as Geocoordinates -- whether as a point, Point/radius, track, polygon, etc.), and "Event" is defined by one Location instance plus the other two space-time dimensions (Z & T; effectively represented as elevation, depth and date/time). I'd be happy to explain why we came to this conclusion, but that's another thread.
The point is that I think "Event" should remain as an abstract four-dimensional address, created as an instance to capture space-time information for something else. In DwC, that "something else" is an Occurrence.
Within the confines of existing DwC, "HumanObservation" comkes closes to being a subclass of Occurrence. However, there is still one missing class that I believe we need to complete the core ontology space of DwC -- which is what we refer to as "Evidence", and Darwin-SW refers to as "Token" (https://code.google.com/p/darwin-sw/). Our model draws the lines slightly differently from the diagram for D-SW, but in general they represent a convergence of thinking on the relationships among DwC classes.
In answer to Steve's question:
dwc:HumanObservation rdfs:subClassOf dwc:[Occurrence]
But what would I gain by doing that? What would it prevent me from doing?
I'm not technically savvy enough to answer that question from an implementation perspective; but from a DwC comprehension perspective, it moves us a step closer to mutual understanding of how to transform DwC content into a functional data model. We all kinda/sorta know that already, but as evidenced by the different perspectives of "HumanObservation as a subclass of Event" vs. "HumanObservation as a subclass of Occurrence" just now revealed & expressed, it probably wouldn't hurt to be more explicit about these sorts of things in DwC documentation.
-----Original Message----- From: tdwg-tag-bounces@lists.tdwg.org [mailto:tdwg-tag- bounces@lists.tdwg.org] On Behalf Of Steve Baskauf Sent: Saturday, August 08, 2015 2:47 AM To: Bob Morris Cc: tdwg-tag@tdwg.org Subject: Re: [tdwg-tag] "Class" attribute in DwC
I think that this has been left intentionally vague because at this point
we don't
have well-defined relationships among Darwin Core classes. It seems to me that placing the class terms on the same line are a clue that they are
somehow
related, but it isn't apparent to me that the subsequent terms are always special cases of the left-most terms. I can provide an example where a LivingSpecimen isn't a MaterialSample because it was never collected. I
can
also imagine Event instances which include many HumanObservations (i.e. Event serves to group observations, not to serve as a superclass for observations).
There have been various attempts to lay out how the Darwin Core classes
are
related to each other. But I'm not aware that there has ever been a
consensus
on it. That's why the RDF Guide didn't touch the issue. We were afraid
that the
guide would never be finished if we took up that subject.
I think it would be an excellent exercise to try to lay out how Darwin
Core
classes are related to each other. But first, I would suggest that we lay
out the
use cases that we intend to satisfy by nailing down those relationships,
then
show how establishing those relationships help us. For example, I could suggest that we establish that
dwc:HumanObservation rdfs:subClassOf dwc:Event.
But what would I gain by doing that? What would it prevent me from doing? Steve
Bob Morris wrote:
The current DwC Terms [1] (carrying Identifier http://rs.tdwg.org/dwc/2015-03-19/terms/ and Date Modified: 2015-06-02 ) is confusing (confused? silent? ) about the relation of the "sister classes" to the terms intended (?) to be used therewith. For example, dwc:Event, dwc:MachineObservation, and dwc:HumanObservation could reasonably(?) all have dwc:eventDate applied to them. But http://rs.tdwg.org/dwc/terms/index.htm#eventDatesuggests Class=dwc:Event.
Now it's human-clear that for each of the "multiple" boldface lines in the index, the second and subsequent terms are meant to be special cases of the left most one. What I can't see is whether [1] intends to encourage (require?) this in some explicit way, and where that explicit way is to be found. (I had a dream that the DwC RDF Guide might take a position....) .
Thanks.
--Bob p.s. I concede that some answers might lurk in the ongoing move of resources to http://tdwg.github.io/dwc/terms/. My second dream was that tdwg.github.io does Content Negotiation and curl would rescue me....
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