[tdwg-content] Comments on Cam's RDF practical details of recording a determination What is an Occurrence?

Cam Webb cwebb at oeb.harvard.edu
Thu Oct 28 14:08:22 CEST 2010

Hi Steve,

Thanks for taking the time to work through my example.

> (I'm not used to the Turtle serialization but managed to translate it 
> into XML which is the way I "think" about RDF).

[ Everyone has their favorite tools, but in case anyone is looking for RDF 
tools, I really recommend:

   - Emacs, with n3-mode by Hugo Haas for writing Turtle, and nXML for
     working with RDFXML
   - Redland's <http://librdf.org/> rapper for turtle-to-rdfxml and roqet
     for SPARQL queries
   - Rapper also converts turtle to dot files, and dot from the graphviz
     library can make jpegs of the network ]

> Q2-4.  If the "token" is separated from the Occurrence, then 
> dwc:recordedBy is a property of the Occurrence and dcterms:created and 
> dcterms:creator are properties of the token (if it's a create-able 
> thing).

Is there any benefit to specifying both OccurrenceX dwc:recordedBy PersonY 
and TokenX dcterms:creator PersonY?  If not, which is the more `natural' 
home for the information?  I think it would be TokenX dcterms:creator 

> 1. After considerably thought, I've decided that I don't want to use 
> direct access URLs for images as their identifying URIs.

This is an important point - but does of course make things a bit more 
difficult from a programming point of view.

> ... if we can use them in this way, it greatly reduces the number of new 
> terms that would have to be created to express DwC in RDF (i.e. we don't 
> need to make up dwc:hasOccurrence).  The downside to this is that few 
> (none?) of the relationships that could be expressed by xxxxxxID terms 
> have inverse properties defined.  I made up a few in the sernec: 
> vocabulary, but the need for such terms would have to be discussed at 
> some point in a future RDF task group.

I'd actually be in favor of coining new terms like dwc:hasOccurrence, 
because a term xxxxxxID seems to imply that the object of the triple is 
not the URI of the resource itself, but some additional identifier.

> I don't know enough about how semantic clients work to know if just 
> providing the properties in one direction would be good enough for the 
> client to infer the inverse relationship and make use of it as 
> necessary.

I think the inverse relationships would be put into the OWL ontology that 
officially specified all the TDWG RDF terms, along with domain and 
ranges, etc.



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