This question came up in an off list discussion, and I admit I find the
area pretty confusing, so I'm not quite sure whether (a) my
understanding is correct or (b) there's a problem here or not...
DCMI uses PURLs for the URIs for all the DCMI terms, and issuing an HTTP
GET of such a PURL generates a redirect by the OCLC resolver to a
http://dublincore.org/... URI. Those dublincore.org URIs include
fragment identifiers. So e.g.
http://purl.org/dc/elements/1.1/title redirects to
http://dublincore.org/2003/03/24/dces#title
According to section 4.1 of http://www.ietf.org/rfc/rfc2396.txt
the optional fragment identifier, separated from
the URI by a crosshatch ("#") character, consists of additional
reference information to be interpreted by the user agent after the
retrieval action has been successfully completed.
and
The semantics of a fragment identifier is a property of the data
resulting from a retrieval action, regardless of the type of URI used
in the reference. Therefore, the format and interpretation of
fragment identifiers is dependent on the media type [RFC2046] of the
retrieval result.
So, for example, RFC2854 http://www.ietf.org/rfc/rfc2854.txt
specifies that for a document with MIME type text/html:
the fragment identifier
designates the correspondingly named element; any element may be
named with the "id" attribute, and A, APPLET, FRAME, IFRAME, IMG and
MAP elements may be named with a "name" attribute.
For text/xml, RFC3023 http://www.ietf.org/rfc/rfc3023.txt says
As of today, no established specifications define identifiers for XML
media types. However, a working draft published by W3C, namely "XML
Pointer Language (XPointer)", attempts to define fragment identifiers
for text/xml and application/xml. The current specification for
XPointer is available at http://www.w3.org/TR/xptr
However, at present the document http://dublincore.org/2003/03/24/dces
appears to be served with MIME type text/plain. I'm not clear whether
fragment identifiers are defined at all for text/plain, but it doesn't
seem like it?
So is that a problem for using the redirect of
http://dublincore.org/2003/03/24/dces#title ?
The recent W3C RDF draft specs suggest the use of a MIME type
application/rdf+xml
http://www.aaronsw.com/2002/rdf-mediatype.html
This spec explicitly says rdf:ID and rdf:about attributes define
fragments. The served document does have an attribute
rdf:about="http://purl.org/dc/elements/1.1/title".
But even if the document was served as application/rdf+xml, this doesn't
quite seem to address the problem of what is designated by
http://dublincore.org/2003/03/24/dces#title
Does it actually matter?! I'm really not sure! If someone tells me
authoritatively it doesn't, then I'll go away happy(ish)...(maybe!)
It just seems there _may_ be a problem somewhere there at the moment in
that the use of the URIref http://dublincore.org/2003/03/24/dces#title
doesn't seem to "fit" very well, either with a MIME type of text/plain
(as at present) or of application/rdf+xml (as the recent specs suggest).
Pete
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