Hi Karen,

> The example in the RDA document of the (blank node) publisher 
> element with its sub-elements is not, to my mind, the best 
> example for thinking about the issue of sub-elements in RDA. 
> As you propose, the publisher element is generally singular, 
> and therefore instances of multiple locations or other 
> sub-elements will not cause confusion. There are many other 
> elements (I don't know if element is the right term, but I 
> think that's what the document uses) that do have 
> sub-elements and can appear more than once. A good example of 
> this is a person (author, creator, collaborator). A person 
> can have a name, dates (birth or "flourished"), affiliation 
> (as with a research institution), titles, roles. And of 
> course any given description may have more than one person. 
> This is a situation that I believe does not occur in DC, and 
> therefore may not be covered in the DCAM. (Then again, I 
> could be totally wrong about that, in which case please send 
> a correction. ;-))

This "one-to-many" (or indeed "many-to-many", as the same person may be
the creator of many books) case _is_ covered in the DCAM description
model, and exactly that example is used in the DCAM document. ;-) It is
implemented through the notion (described in section 2.4 of [1] that:

> Each non-literal value may be the described resource in a separate
description within the same description set - for example, a separate
description may provide metadata about the person that is the creator of
the described resource.

i.e. if we are describing a book or whatever and, say, the three persons
who jointly created that book (including their names, dates of birth etc
- each different for each person, as you say), then, using the DCAM
description model, that would be represnted as  

- a description of the book B1, made up of various statements "about"
the book including two statements referencing the dc:creator property

- a description of person P1, made up of various statements "about" the
person
- a description of person P2, made up of various statements "about" the
person
- a description of person P3, made up of various statements "about" the
person

This is an example of why I think it is important that the RDA docs
consider/present the DCAM description model "as a whole", _including_
the concepts of statement, description and description set. Taking
concepts like "value string" and "value surrogate" out of that context
doesn't really provide the whole picture, it seems to me.

I think this also illustrates what I was trying to say about needing to
consider:

(i) "what RDA wants to say about the world", and 
(ii) "how to say those things about the world using the DCAM description
model and RDF model"

- especially for the sub-elements - on a case by case basis, rather than
trying to establish a single global "rule" for mapping the different
"types" of RDA construct to DCAM/RDF constructs.

Where the use of elements & sub-elements in RDA is really just a simple
"grouping" construct, and there is still a one-to-one relationship
between the bibliographic resource and the "grouped thing" (e.g. the
publication statement case in RDA Element Analysis section 2.1) then it
seems to me there is no real _need_ to model that "grouped thing" as a
resource in its own right (the blank node in the RDF graph). You _can_
still model it like that if you want, but, as Brad was arguing, I think,
it introduces some (arguably unnecessary) complexity. 

OTOH, where the use of elements & sub-elements in RDA is used to model a
one-to-many or many-to-many relationship, between the bibliographic
resource and some other resource (e.g. a person, a place, whatever) and
it is a requirement to describe attributes of that other resource, then
it _is_ necessary to treat the things as distinct resources and, in the
terms of the DCAM to provide two distinct descriptions of tose two
distinct resources. 

Cheers

Pete

[1] http://dublincore.org/documents/2007/06/04/abstract-model/

---
Pete Johnston
Technical Researcher, Eduserv Foundation
Web: http://www.eduserv.org.uk/foundation/people/petejohnston/
Weblog: http://efoundations.typepad.com/efoundations/
Email: [log in to unmask] 
Tel: +44 (0)1225 474323