[tdwg-content] Expressing some relationships in DwC?

Chuck Miller Chuck.Miller at mobot.org
Wed Oct 26 21:02:35 CEST 2011

"perhaps we should examine how best to use this already-existing DwC

I'm thinking we need much more clarity for the TDWG community on this
very point.  What are the best uses of DwC terms? 

Distinguishing the uses/methods/techniques from the DwC terms themselves
would be very useful I think.  In any particular discussion, it would be
helpful if it were clear if the use in discussion was about using DwC in
a Generic Darwin Core XML Schema, Simple Darwin Core XML Schema, or
Darwin Core Text Schema (all defined in the Standard) or in a DwC-A
package or an RDF triple structure or some other.  Without structure or
relationships, terms are just terms aren't they?  Maybe I'm just
uneducated in this area.


-----Original Message-----
From: tdwg-content-bounces at lists.tdwg.org
[mailto:tdwg-content-bounces at lists.tdwg.org] On Behalf Of Richard Pyle
Sent: Wednesday, October 26, 2011 1:25 PM
To: 'Steve Baskauf'
Cc: tdwg-content at lists.tdwg.org; mdoering at gbif.org
Subject: Re: [tdwg-content] Expressing some relationships in DwC?

>  Well, I guess one could make the case that people who are not 
> interested in RDF might want a DwC-only way to express this.

Maybe "not interested" is not the best way to put it.  Perhaps "not

> I guess my point was that we seem to be talking about trying to invent

> a method to accomplish something where there already is a 
> well-established way to do it.  DwC at the present has a very "flat"
> database orientation and I think the resource-relationship terms were 
> introduced to allow for a "flat" way to describe resources that aren't

> really flat (i.e. 1:M or M:M).

Agreed.  But resourceRelationship is already in there, and as we both
seem to have discovered, nobody appears to be using it.  So...I think we
at least need to clarify how it's supposed to be used in a DwC context;
or we should let it die a slow, quiet death of non-use.  I guess I'm OK
either way; but given that it exists, and given that we seem to have
people who don't want to go all the way to RDF triples for all data
exchange purposes (yet), perhaps we should examine how best to use this
already-existing DwC class, modify it as needed to make it actually
useful to those who want to use it, and let it die after we're all
pumping our data out via RDF that works against a solid, stable

> It's based on the term definition and examples at 
> http://rs.tdwg.org/dwc/terms/index.htm#relationshipOfResource
> which recommend a controlled vocabulary and give strings as the only
> I think that in keeping with other precedents in DwC your suggestion 
> of "relationshipOfResourceID" might be better.


> Well, in terms of the type for the subject, I don't think there is any
reason to
> create a new term for that.  There is already rdf:type to do exactly

Well...there's also dcterms:type, which is already part of DwC.  The
problem, though, that this would apply to resourceRelationshipID (i.e.,
the "type" of relationship itself); not to the resourceID.  Technically,
you'd need to resolve resourceID to retrieve dcterms:type for the
subject item.  I don't know how rdf:type is intended to work in this

> Whether it would matter if DwC imports that term or not, I don't know.

How is it different from dcterms:type?

> It is certainly already "well known".  relatedResourceType could be a
> to accomplish what you want for the object.  We are still left with 
> the
> that there is no consensus about what are the core "types" (which I
> to be equivalent to the question of what are the core classes) in our
> I've argued for adopting the DwC classes where they will do the job, 
> but I
> heard too many people express support for that and there are necessary
> that don't exist (yet) within  DwC (e.g. a class for agents).

Can't DwC simply import terms from foaf, like it does with dcterms?

> Also, there are classes in the TDWG ontology that may or may not 
> overlap
> DwC classes (most notably dwc:Taxon).  Do we use therm?

Perhaps.  I guess it would depend on demand and specific use cases.

> So in order for this to be of much value, it seems to me that there is

> a
need to
> hash out the core classes/types.  I was hoping the RDF group would 
> take
that up,
> but it's not clear to me that there is support for doing that at this
> (was it discussed at the meeting?).

Yes, it was discussed at the meeting -- at least in the BiSciCol group
and the RDF group.  There seemed to me a growing interest in
resurrecting a discussion about a TDWG ontology, to see if it could be
finished.  Not in full-spec detail; but at least to the level of the DwC
classes (and other like-level entities).  I only caught part of the
discussion at the RDF group, but Cam was there.  It seemed to me that
several people were citing the Darwin-SW ontology as a starting point

> > The day when those are reality will
> > certainly come (I hope!), but in the mean time, we still need an
> > mechanism for certain content that is more complex than what can be 
> > met
> > DwCA.
> I agree.  I don't see any reason why the same relationships that one 
> can
express in
> RDF triples couldn't be expressed in a database table.  But some of 
> the
issues that
> must be addressed to make that work are (in my mind) the same ones 
> that
> to be addressed to make RDF work as a metadata transfer mechanism.
> They could probably both be worked out at the same time to some

Yes, agreed!  They should absolutely be worked out at the same time.

> Well, I actually wasn't so much concerned with the mechanics of 
> actually handling the RDF as the fact that it makes more sense to me 
> to have a generic URI to describe a particular kind of resource 
> relationship than to

> have to parse out and interpret a string for every relationship that 
> is to be described.  One of the points of RDF is that it doesn't have 
> a single representation (e.g. it doesn't have to be represented as
> But the subject, predicate, object relationship is basic and that's 
> pretty

> much what we are talking about here.

OK, I agree.  It could be that resourceRelationship is a "gateway drug"
to get people into thinking in terms of triples.


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