Suggestion: XLink resource semantics should use Dublin Core

The resource semantics section specifies attributes "title" and "role".
http://www.w3.org/XML/Group/1999/05/WD-xlink-19990505 specifies

The Dublin Core effort has defined 15 elements which they think provide
minimal metadata "for author-generated description of Web resources":
ftp://ftp.isi.edu/in-notes/rfc2413.txt  and
http://purl.oclc.org/dc/about/element_set.htm


        Content          Intellectual Property       Instantiation
        -----------      ---------------------       -------------
        Title                 Creator                  Date
        Subject               Publisher                Format
        Description           Contributor              Identifier
        Type                  Rights                   Language
        Source
        Relation
        Coverage

I suggest that the Dublin Core elements and the XLink resource semantic
attributes are similar enough that they should be combined: title is the
same, and DC.RELATION seems much the same as xlink:role: "
   An identifier of a second resource and its relationship to the
   present resource.  This element is used to express linkages among
   related resources.  For the sake of interoperability, relationships
   should be selected from an enumerated list that is currently under
   development in the workshop series."

Perhaps the "Instantiaton" elements are not as needed, but I cannot see the
harm in supporting everything. Perhaps information like type is not as
needed, given the emphasis on content negotiation; but if the link is part
of a system aiming to describe actual resources rather than request them in
some convenient format, even data such as "type" is useful.

This has several benefits:

1) It frees XLink IG from having to figure out or justify its decisions on
what kinds of resource semantic metadata are required;

2) It integrates XLink into the Dublin Core framework; Dublin Core has been
well-received, and it would seem unfortunate to diminish it;  In particular,
it allows resource discovery using the link rather than having to retrieve
the resource;

3) It integrates Dublin Core into the XLink framework (much needed, in view
of the Dublin Core people's seeming uninterest in standardizing particular
markup conventions--without which their metadata is unuseable by automated
discover tools);

4) It provides a way of annotating Web resources such as graphics with
Dublin Core metadata; this is very much needed in particular for Digital
Library projects;

5) It takes care of some niggling issues, for example the provision of
human-readable copyright notices on links.  I would suggest that it would be
quite nice for users if moving a mouse button over an HTML href resulted in
a Dublin Core record popping up: on one of my QAML stylesheets I
experimented in providing some metadata on top of a link (if you have IE5 go
to http://www.ascc.net/xml/resource/qaml/dc-faq-xsl2.html and move your
mouse over the blued hrefs: you get the "gist". If you click on the link,
you get the full answer: move your mouse over and you get the "creator".)

So, I suggest that the resource semantics elements "role" and "title" be
renamed dc:relation and dc:title, and that all the other DC elements be made
available as attributes on XLinks.  It would probably be prudent to also
define the minimum "qualified dublin core" attributes to allow specification
of the controlled vocabulary in use. In particular:
    dc:relation.schema
    dc:subject:schema or dc:subject.vocabulary
    dc:type.schema
    dc:coverage.schema
    dc:date.schema

This is quite a large set of extra attributes (20!) but I think they are all
uncontraversial if the decision is taken that the XLink resource semantics
attributes and the Dublin Core elements are for the same purpose.

Rick Jelliffe

Received on Monday, 10 May 1999 08:30:41 UTC