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....