Well, I would respectfully disagree that we are building an ad hoc model here.  We are actually at the end of a rather lengthy process of trying to develop a consensus of what exactly an Occurrence is. 

Since at least October of 2009, there has been discussion on the tdwg-content list about the meaning of Occurrence.  I realize that because of the large number of posts, not everyone had the time to keep up with that conversation and parallel discussions on the topic of Organisms/Individuals, and CollectionObjects/Samples/Tokens.  The suggestion was made that someone take the time to summarize these discussions for those who didn't have the time to keep up with them as they were happening.  I have expended a rather large amount of time to do exactly that: you can find a somewhat chronological summary at http://code.google.com/p/darwin-sw/wiki/TdwgContentEmailSummary and topical summaries at http://code.google.com/p/darwin-sw/wiki/ClassOccurrence , http://code.google.com/p/darwin-sw/wiki/ClassIndividual which have links to the many of the individual posts that were made on those topics. 

What emerged from these discussions was what appeared (to me at least) to be a consensus about what an Occurrence was.  I will refer you to the http://code.google.com/p/darwin-sw/wiki/ClassOccurrence page for some of the definitions that were suggested.  This consensus made the distinction between the record that an organism was present at a particular time and place, and the evidence (if any) that was used to document the Occurrence.  The proposal that John made is a reflection of the apparent consensus that came out of that discussion. 

The Darwin Core standard has a process in place for making additions and changes to the terms in its vocabulary.  That process involves discussion, consensus-building, and the defining and adoption of new terms (or modification of the definitions of existing terms) when they are needed by a significant portion of the TDWG community.  That process has taken place in this instance and I believe that John is right to "call the question" on these new term proposals.  TDWG has a reputation as an organization where people talk endlessly and nothing ever really gets accomplished.  We have an opportunity here prove that reputation wrong.  If we simply start asking the same questions (which have already been discussed ad nauseum) over again without making an actual decision on the proposal, then what we are doing really IS a waste of time.  I, for one, have no interest in spending any more time on this issue.  So I would recommend that people who want to comment about the proposed definitions of Occurrence, Organism, and CollectionObject review the discussion summaries that I've noted above before restarting conversations that have already pretty much been run into the ground. 

I would also respectfully disagree that through these proposals we are building a complex model by adding terms for CollectionObject and Organism.  The proposals are ONLY for adding terms.  Nothing in those proposals models how the new classes are related to any other existing classes in Darwin Core in a formal way (e.g. through OWL or RDFS).  There have been repeated calls for further discussion that would build a consensus about a more complex model, possibly built on top of a foundation based on Darwin Core classes and property terms.  As a consequence, we are attempting to charter a group to discuss more complex RDF models that can be used by those who need them (see http://code.google.com/p/tdwg-rdf/wiki/CharterOfIG).  As you suggest, the core members of the proposed group includes representation from the Observations community as well as other constituencies within TDWG.  But that discussion is really just starting.

With regards to Markus' concern about whether people will be able to know whether somebody is talking about a "new-style" Occurrence or an "old" Occurrence, I would assert that the "old" Occurrence didn't really have a clear meaning.  If you review the summary of the discussion on Occurrence, you can see that it was used to mean at least three different kinds of "things" by different people.  What John is actually doing with his proposal is to add clarity about what an Occurrence is where it didn't exist before.  I think that is a good thing.  If, by the "old" kind of Occurrence people are meaning that Occurrence is a fancier name for PreservedSpecimen (which I believe is how some people in the museum community are thinking of it), then I would say that such a characterization is incorrect (based on the apparent consensus) and that clarifying the incorrectness of that view is a really good thing.

Steve

Éamonn Ó Tuama (GBIF) wrote:
It would be good to hear from someone who is familiar with the work going on in the Observations Task Group and could explain how a generic model for observations/measurements (e.g. OBOE) might help sort out these issues. It seems to me that we are trying to build in an ad-hoc manner an increasingly complex model on top of DwC which is really just a glossary of terms. That does not seem like a good approach - but I'm no modeller :-) 
_Éamonn

-----Original Message-----
From: Dag Endresen (GBIF) [mailto:dendresen@gbif.org] 
Sent: 13 September 2011 12:18
To: "Markus Döring (GBIF)"
Cc: tdwg-content@lists.tdwg.org; Éamonn Ó Tuama
Subject: Re: [tdwg-content] Occurrences, Organisms, and CollectionObjects: a review

 Hi Markus,

 I believe that the discussion here originates from the view that the 
 "CollectionObject"/"Sample" is a different thing from the "Organism" - 
 and that there can be a relationship between CollectionObjects/Samples 
 and Organisms that could be difficult to describe if these things are 
 identified as the same think (occurrenceID). Do you think that the 
 "Occurrence" would be seen as a thing different from the proposed 
 CollectionObject/Sample and Organism - or as a super-class that would 
 include CollectionObjects/Samples and Organisms? Would the semantics of 
 Occurrence change?

 I fully share your view that the Darwin Core Archive (DwC-A) would not 
 be suited to share the full complex relationship between entities - even 
 if persistent identifiers would be used. However if we start to describe 
 and include other things (core types) than only the taxon and 
 occurrences then perhaps the DwC-A could be a useful way to provide a 
 simple list of these entities? This could perhaps provide easier 
 indexing and discovery of these new entities?

 Dag



 On Tue, 13 Sep 2011 10:03:00 +0200, Markus Döring (GBIF) wrote:
  
I have to say that the change in semantics to the Occurrence class
makes me a bit nervous.
Can someone try help fighting my fears?

DarwinCore has no versioning of namespaces, so there is no way for a
consumer to detect if its an old style Occurrence or a new one. I am
currently parsing various RSS feeds and even though its a mess having
to parse 10 different styles I am glad that at least the designers
made sure they all have their own namespace! Also removing or 
renaming
terms might cause serious problems. Would discrete versions of dwc
with their own namespace hurt?

Another observation relates to dwc archives and its star schema. As
an index to data that has been flattened there is no problem with 
more
classes and core row types, but if you want it as a way to transfer
complete normalized data it will not work. But that never really was
the intention and I simply wanted to stress that fact.

Markus



On Sep 9, 2011, at 4:52 PM, Steve Baskauf wrote:

    
Richard Pyle wrote:
      
I'm also wondering if we necessarily need to "break" the 
traditional view of
the "Occurrence" class in order to implement Organism and 
CollectionObject.
As long as we keep in mind that DwC is a vocabulary of terms 
focused on
representing an exchange standard (rather than a full-blown 
Ontology),
perhaps Occurrence records can continue to be represented in the 
traditional
way as "flat" content, but the Organism and CollectionObject 
classes allow
us to present data in a somewhat more "normalized" way in those
circumstances that call for it (e.g. tracking individuals or groups 
over
time [Organism], or managing fossil rocks with multiple taxa
[CollectionObject] -- to name just two).

        
I've been thinking about this issue of "backward compatibility" with
respect to Occurrences if the CollectionObject/Sample/Token/whatever
class is adopted.  I really don't think it is going to be as big of 
a
deal as people are making it out to be.

It seems to me that the main problems arise in two areas: when one 
wants
to be clear about typing and when one wants to express relationships 
in
a system where it is possible to do through semantics (like RDF).  
In
that kind of circumstance, it's bad (oh yeh, I forgot - the term is
"naughty") to say  something like
resourceA hasOccurrence resourceB
when resourceB isn't actually an Occurrence.   "Wrong" typing also
happens all the time because the classes don't exist (yet) to do the
typing correctly.  As a case in point, in the Morphbank system, I 
have
multiple images of the same tree.  In that system the tree is typed 
as a
"specimen".  That is totally wrong because the tree isn't a 
specimen,
but what else is it going to be typed as?  There isn't (yet) an
appropriate class to put it in.

Although these two problems (wrong typing and using a term with the
wrong kind of object which are actually different manifestations of 
the
same class-based problem) are naughty, realistically very few people 
are
actually using a system that is "semantic-aware" (e.g. serving and
consuming RDF) so right now making those mistakes doesn't really 
"break"
anything.  Most data providers are using traditional databases or 
even
Excel spreadsheets where the DwC terms are just column headings with 
no
real "meaning" other than what the data managers intend for them to
mean.  So if a manager has a table where each line contains a record 
for
a specimen and has a column heading for a column entitled
"dwc:catalogNumber", there isn't really anything other than an idea 
in
the manager's head that the catalogNumber is a property of a 
specimen or
Occurence or CollectionObject.  If each line in the database table 
is
"flat" such that one specimen=one CollectionObject=one Occurrence, 
all
that is required to make catalogNumber be a property of a
CollectionObject instead of an Occurrence is a different way of 
thinking
in the managers mind because there are really no semantics embedded 
in
the table.  We are already doing this kind of mental gymnastics with
existing classes like dwc:Identification .  If our hypothetical 
database
manager has a column heading that says "dwc:identifiedBy" in the
specimen table, that is really a property of dwc:Identification, not
dwc:Occurrence but again that is a distinction that is only going to 
be
made in the manager's mind.  Making the distinction really only 
becomes
an issue when the database stops being "flat" for a particular
relationship, e.g. if the database wants to allow multiple
Identifications per specimen record.  Then the database structure 
must
be changed accordingly to accommodate that "normalization".

What we have here at the present moment is a situation where data
providers don't have any way to have anything but "flat" records 
where 1
specimen=1 Occurrence=1 Organism.  By adding the Organism and
CollectionObject classes, we allow people who need or want to have 
less
"flat" (=more "normalized") databases to have something to call the
entities that are represented by the new tables they create to 
handle
1:many relationships instead of 1:1 relationships.  Anybody who only
cares about 1:1 relationships really doesn't need to worry about the
fact that the new class exists, just as people currently don't have 
to
worry about the Identification class if they only allow one
Identification per specimen in their database.

So I guess what I'm saying is that if a database manager has a table
labeled Occurrence, they really don't have to freak out if we now 
tell
them that their table actually should be labeled CollectionObject as
long as there is only one CollectionObject per Occurrence.  They 
didn't
freak out before when we told them that they should call their table
"Occurrence" instead of "Observation" or "Specimen" in 2009, did 
they?

I think what I'm saying here is what Rich was trying to say in the
paragraph I quoted, but I'm not sure.

Steve

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

postal mail address:
VU Station B 351634
Nashville, TN  37235-1634,  U.S.A.

delivery address:
2125 Stevenson Center
1161 21st Ave., S.
Nashville, TN 37235

office: 2128 Stevenson Center
phone: (615) 343-4582,  fax: (615) 343-6707
http://bioimages.vanderbilt.edu


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

postal mail address:
VU Station B 351634
Nashville, TN  37235-1634,  U.S.A.

delivery address:
2125 Stevenson Center
1161 21st Ave., S.
Nashville, TN 37235

office: 2128 Stevenson Center
phone: (615) 343-4582,  fax: (615) 343-6707
http://bioimages.vanderbilt.edu