[tdwg-content] practical details of recording a determination What is an Occurrence?

Cam Webb cwebb at oeb.harvard.edu
Mon Oct 25 10:45:41 CEST 2010

Dear Hilmar,

Thanks for this insight.  I have to admit to no prior experience of 
mereology, but the desire to find a solution to how to semantically encode 
morphological observations in a fashion which many can agree upon prods me 
to reply.  Sorry if I am way in out of my depth and it shows!

>> We can also employ the OBO relational ontology (ro) to indicate that a 
>> fruit is ro:part_of the particular space-time Occurrence of an 
>> Individual (this might require a bit more discussion!).
> I don't think you can do that actually, given the definition of the relation 
> [1]. I.e., to me the definition sounds like it is true meristic parthood that 
> is meant here (and for which it is applied in the uses that I have seen). The 
> fruit has some role in Occurrence, but isn't a part of it in the sense of 
> meristics, don't you think?

If we consider the occurrence to be the intersection of the individual 
with an (observation) event in a particular space and time (e.g., tzxy0), 
I think a fruit_txyz0 is indeed part of plant_txyz0, fulfilling the 
ro:part_of definition of:

   ``For continuants: C part_of C' if and only if: given any c that
     instantiates C at a time t, there is some c' such that c' instantiates
     C' at time t, and c *part_of* c' at t.''

The alternative to making the fruit a part of the dwc:Occurrence is to 
make it a part_of the sernec:Individual, which could then be observed via 
the OBOE terms, at a particular place and time (although strangely there 
seems to be no date/time observation terms in OBOE).  This second 
alternative would be less satisfying though, given that dwc:Occurrences 
have already been specified to include Observations. Maybe using 
dcterms:isPartOf would be OK, since it is less precisely defined?

> Also, the quantification doesn't match: If A ro:part_of B, then all 
> instances of A part_of some instance of B. Obviously, there are some 
> fruits that haven't been recorded in an occurrence.

I agree with this, but this must surely be a generic issue within the 
whole OBO/organismal annotation world - often a phenotype must be recorded 
for c, which is part_of c', without having considered every instance of C.

This is clearly an issue to take up with the TDWG Observations WG, and 
I'll post to the new post-Wood's Hole list shortly.  If any of you have 
any suggestions for how to progress with this, I'd appreciate them.



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