[tdwg-content] domains of object properties. was Re: DwC for the semantic web

Steven J. Baskauf steve.baskauf at vanderbilt.edu
Fri Apr 29 12:58:47 CEST 2011

Well, at the risk of being scolded, we actually DID declare some classes 
to be disjoint in the ontology.  Those classes are Location, Event, 
Occurrence, IndividualOrganism, Identification, and Taxon.  Based on the 
discussion of Oct/Nov, it was clear to us that each of those is a 
distinct type of thing.  From the standpoint of DSW, it is "wrong" to 
type something as both a Location and an Occurrence, or a Taxon and an 
Event.  If one does, a reasoner should have a fit.  That is why we have 
taken care on the Wiki pages to define what we consider each class to be 
and to support that reasoning with references to either publications or 
discussion that took place on the list.  As I said in a previous email, 
the point of DWS is to provide clarity about what an RDF file says, not 
to encourage creativity. 

You should note that Token is not included on the list of classes that 
are mutually disjoint.  Another point of discussion between Cam and I 
was whether there actually should be a class called "Token".  In the 
end, we decided to include it with the understanding that it would 
probably have at least two rdf:type's most of the time.  There is 
nothing wrong with that.  A digital image can be a dsw:Token and also be 
a mrtg:MultiMediaObject, dctype:StillImage, and foaf:Image if one cares 
to assign it all of those types directly, or indirectly via making it 
the object of a property that has such a range declaration (such as 
foaf:depiction).  A Token can also be an IndividualOrganism if it's a 
living specimen.  I consider typing something to be a message to users 
which informs them of what kinds of properties to expect to find out 
about it.  If a resource is a Token, we would expect it to have the 
kinds of properties that evidence has, such as dsw:isBasisForId aor 
dsw:evidenceFor and maybe dwc:catalogNumber.  If it is also a 
dsw:IndividualOrganism, then we expect it to have properties like 
dsw:hasIdentification and dsw:hasOccurrence but if it's a still image 
then it should have properties like dcterms:creator and intellectual 
rights properties. 

Perhaps we do deserve a scolding for doing this.  But as I have said 
earlier, the purpose of DSW is to facilitate clear and unambiguous 
communication in RDF, primarily for people who want to combine metadata 
from different institutions based on diverse kinds of tokens (preserved 
specimens, images, living specimens, observations, tissue samples, 
etc.).  That really isn't possible if each institution has their own 
personal idea of what something like an Occurrence is.  People who have 
other objectives may be best served by creating a different DwC-based 
ontology that meets their own needs. 


Mikel Egaña Aranguren wrote:
> Using a domain for a property will only be a problem if disjoints are 
> stated. Even more, someone else could add further domains to trigger 
> further rdfs:type inferences.
> We should be careful, nonetheless, when using domains.
> I'm saying this cause the word "constraint" does not quite represent 
> what a domain is, and we should avoid it, since it creates confusion on 
> OWL newcomers.
> Very good point though.
> On og., 2011.eko apiren 28a 22:14, Bob Morris wrote:
>> I´ve been in Ecuador for two weeks with only a few hours of internet
>> contact. Flying from Quite tonight.  So I´ve only scanned the Design
>> Document and may have done so too hastily.  I´ll have more time next
>> week to look at it and the ontology.  However, meanwhile, I´ve posted
>> the following unsurprizing comment there, and hope that anyone who
>> responds here will also respond there.
>> -----
>> It´s a little hard to understand why DSW object properteries should
>> have domains but data properties should not. Keep in mind that the
>> formal semantics of rdfs:domain is that if rdfs:domain P C then any
>> use a P x forces a to have rdfs:type C. This constrains the
>> extensibility of P and probably of the use of other ontologies where P
>> might be useful. Specifying domains tends to close the world somewhat,
>> and I see no advantage to that....Indeed, this is more naughty than
>> anti'naughty sensu Bob Morris.
>> -----
>> --Bob Morris
>> On Wed, Apr 27, 2011 at 9:01 PM, Steve Baskauf
>> <steve.baskauf at vanderbilt.edu>  wrote:
>>> Dear colleagues,
>>> With the exciting development of Semantic Web technologies, many of us already need a way to consistently express DwC in RDF.  In particular, we need it to meet the requirements for GUID resolution (as expressed in the TDWG applicability guide) and to be able to share and aggregate diverse kinds of biodiversity metadata in the Linked Open Data world.
>>> After several months of development, stimulated by the tdwg-content discussions of last Fall, we would like to offer an
>>> ontology for consideration, based on Darwin Core terms:
>>>    Darwin-SW:
>>>      General site: http://code.google.com/p/darwin-sw/
>>>      Using namespace dsw = "http://purl.org/dsw/"
>>> It is a candidate for general usage, but we do not claim it is _the_ solution, and greatly respect the efforts by others to develop similar ontologies, from which we have learned much. However, for DSW, we wanted to use existing DwC terms for classes and data properties whenever possible and only create new terms when there were no existing terms that would do the job.  We did feel that there was a need for clarity in how resources should be typed (i.e. rdf:type property) and for object properties that expressed the relationships among classes unambiguously. Please see the Rationale, DesignPrinciples and ClassesAndTypes wiki pages at the above address.
>>> In the ontology, we sought to embody relationships among classes based on our perception of the community consensus of what the classes represent and how they are related to each other, as expressed in posts to the tdwg-content list.  Thus each class is documented carefully on the wiki with hyperlinked references to specific tdwg-content posts. We also sought
>>> to clarify or resolve issues that were raised in the list discussion, most notably the relationship among Occurrences and the evidence that documents them (i.e. tokens), and the role of "individuals".  See wiki pages for the Token, Occurrence, and IndividualOrganism classes.
>>> The ontology is now in use at http://bioimages.vanderbilt.edu/, and we intend to use it more widely.  We would value your opinions on the fitness of this ontology as a general solution for consistently expressing DwC concepts in RDF.
>>> Sincerely,
>>> Steve Baskauf and Cam Webb
>>> steve.baskauf at Vanderbilt.Edu
>>> cwebb at oeb.harvard.edu
>>> _______________________________________________
>>> tdwg-content mailing list
>>> tdwg-content at lists.tdwg.org
>>> http://lists.tdwg.org/mailman/listinfo/tdwg-content

Steven J. Baskauf, Ph.D., Senior Lecturer
Vanderbilt University Dept. of Biological Sciences

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