[OAI-implementers] XSD file for qualified DC

Ann Apps ann.apps@man.ac.uk
Fri, 21 Jun 2002 10:16:05 GMT1BST


I will answer Carl's email when I've had time to think a bit more about it. 
But I would like to make a few comments on yours, and in particular 
correct a few DC encodings.
> "dc:identifier is an unambiguous reference to a resource" - citations
> are intended to be unambiguous references. 
I agree with this. But dc:identifier is the identifier of the resource  
the metadata record describes. This applies also to any qualifiers 
of dc:identifier. The proposed qualifier 'citation' is a qualifier of 
dc:identifier. So using dc:identifier or dcterms:citation for a 
reference does not comply with DC recommendations.

> "dc:relation is a reference
> to a related resource" - I believe reference data falls under this
> description.
This is alos my understanding.

> <a_dc>
> <dc:relation>Smith, John (1992) Functional Principles in Functions v5
> 44-50</dc:relation> </a_dc>
> Passed through a citation-aware gateway would produce:
> <a_dcq>
> <dcq:relation.references>
> <dcterms:citation>Smith, John (1992) "Functional Principles in
> Functions" v5 44-50</dcterms:citation>
> <dcq:identifier.citation>
> <dc:creator>Smith, John</dc:creator>
> <dc:date>1992</dc:date>
> <dc:title>Functional Principles in Functions</dc:title>
> <ja:volume>5</ja:volume>
> </dcq:identifier.citation>
> </dcq:relation.references>
> </a_dcq>
Several things about this example:

The accepted way now of encoding DC in XML is to use the 
qualifier name directly within the dcterms namespace (dcq is a 
synonym for dcterms) without its parent element, and not to use 
the dot notation. So <dcq:relation.references> would be written as 
simply <dcterms:references>. 

dcterms:citation is a proposed qualifier for dc:identifier not for 
dc:relation (which already has the references qualifier), so shouldn't 
be nested inside a dc:relation. So the reference as a string could 
be encoded as:

<dcterms:references>Smith, John (1992) "Functional Principles in 
Functions" v5 44-50</dcterms:references>

After that: dcq:identifier.citation, better dcterms:citation, is not valid 
DC nested within a dc:relation. It would be possible to propose a 
similar sub-structure for dcterms:references to that proposed for 
dcterms:citation but it is not currently a valid encoding. But the 
proposed structure of dcterms:citation does not include the 'top-
level' DC elements (creator, date). I assume ja:volume is from 
Herbert's OpenURL email.

Of course the encoding you present will be valid XML given 
appropriate namespace declarations. But it is not valid DC because 
it does not follow DC recommendations. So I would dispute 
whether you should be calling it DC at all. This then becomes an 
argument for Carl's suggested parallel format.

> I've no doubt the same can be achieved through OpenURL, but DC is more
> widely used (so the closer to DC, and the more use of DC elements, the
> greater the adoption will be, hence the greater the interoperability).
The main reason DC is more widely used is that it's been around 
much longer. OpenURL is about citations, DC isn't - it is a basic 
core metadata. I agree that more use of DC will mean greater 
adoption, simply because it has developed a reputation. But using 
DC incorrectly will actually deter interoperability. Using OpenURL, 
as it becomes more widely adopted will increase interoperability.

I am trying to be objective about this, but should probably declare 
my interests - I am chair of the DC-Citation working group and also 
a member of the OpenURL NISO committee.

Best wishes,

Mrs. Ann Apps. Senior Analyst - Research & Development, MIMAS,
     University of Manchester, Oxford Road, Manchester, M13 9PL, UK
Tel: +44 (0) 161 275 6039    Fax: +44 (0) 0161 275 6040
Email: ann.apps@man.ac.uk  WWW: http://epub.mimas.ac.uk/ann.html