DC in XHTML2 - Semantic Web

Message from discussion DC in XHTML2

Al Gilman

More options Jun 9 2005, 2:13 pm

From: Al Gilman <Alfred.S.Gil...@IEEE.org>

Date: Thu, 9 Jun 2005 14:13:28 -0400

Local: Thurs, Jun 9 2005 2:13 pm

Subject: RE: DC in XHTML2

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At 3:01 PM +0100 6/9/05, Mark Birbeck wrote:

>Al,

>>From XHTML 2's standpoint, all you need is the URI for your roles. If that's
>backed up with some RDFS/OWL statements that tell you more about it, that's
>a great bonus, and it's a consequence of XHTML 2 getting it's relationship
>to RDF sorted out. But it is still external to XHTML 2.

>Misha and the IPTC's interest though is in putting subject codes in the form
>of QNames into the object part of the statement, not the predicate part.

That is not how I read the question. As I read the question, that is
not what they want to do; rather that is *where they found a
roadblock in the path to a solution that they were going down.* I
don't think you did the "if that's not the answer, what's the
question?" step to back off to the real requirement.

What I believe they want is a compact notation by which they can
associate content blocks with well-known (much re-used) subject
categories.

So I claim that creating a short QName notation that (sufficiently
formally and authoritatively) expands to "has 'subject' (per Dublin
Core) of 'sports' (per IPTC)" is solving precisely the problem that
they face. And if we were to make 'role' M-ary rather than unary,
this would flow neatly in there.

And even if we don't if fits nicely in 'property' even if each subject
category needs a separate 'property' declaration.

If you wanted to make it mnemonic, it could read

property="iptc:sportsSubject"

where the dc: is hidden because all IPTC subject literals are
designed and documented to conform to the Dublin Core notion of
'subject.'

... or depending on the range of tokens in the IPTC vocabulary,
it could be flattened to

property="iptc:sports"

... because 'sports' was diagnostic as to what DC field was being
populated.

The downside to the latter form is that one *has to* process the
namespace document(s) to formally know that you know a value of
dc:subject when you know the property iptc:sports.

But that's always going to be a tradeoff. Local domains use
local-code names for things that are expressions in the world at
large.

Personally, I think the HTML WG made a mistake in failing to solve
the 'role' requirement with QNames in 'class.'

We are never going to get the preponderance of the Web to be
accessible content until we train people to use semantic 'class'
tokens and style selectors. Not 1:1 class tokens and style rules.

http://tantek.com/log/2004/07.html#classmeaningnotshow

So since we have to fight that war to reclaim 'class' anyway,
why not use it for what it's for?

class="... iptc:sports ... " is the direct solution to Misha's problem.

>So
>whereas we can easily do this:

> <meta property="dc:subject">Chess</meta>

>we unfortunately have to do this:

> <link rel="dc:subject" href="http://codes.com#Chess" />

>In other words you have URIs in one place and QNames in another.

>(Note that if we're really committed to using DC in XHTML 2, then we don't
>need to invent iptc:subject. ;) )

>FINDING A SOLUTION
>I don't think the solution is particularly difficult, but those interested
>in the discussion should be aware that it is also not completely
>straightforward.

>For example, the most likely solution would just involve adding a @resource
>attribute (or some other name) to be used with @property:

> <meta property="dc:subject" resource="codes:Chess" />

>It could be used with @rel/@rev instead, but if we keep it with @property
>then we have effectively compartmentalised the attributes that concern
>'real' linking from those that are about metadata.

>However, the moment we introduce this, we get the @about attribute shouting
>and waving and saying "I want to be a QName, too". This is required, because
>otherwise you can't make statements about the objects you have used in your
>other statements, unless you once again use two different syntaxes.

>We therefore additionally need to introduce a QName attribute for the
>subject position. Since there is no obvious name for this attribute, perhaps
>we should reconsider @resource, and call all of the QName versions of our
>attributes by the same name as their corresponding attribute but with a 'q'
>prefix. This would give us @qabout for the subject, and @qhref for the
>object.

>But then to be consistent, @rel, @rev, @role and @property should really be
>called @qrel, @qrev, @qrole and @qproperty. @rel, @rev, @role and @property
>could be retained, but they must now contain URIs instead of QNames. We
>therefore end up with:

> Subject: qabout about

> Predicate: qrel rel
> qrev rev
> qproperty property

> Object: qhref href
> qrole role

>(Note that @role is a special type of object identifier where the predicate
>is always <http://www.w3.org/2004/06/xhtml2/role>.)

>I don't think that using two attributes to represent the same
>concept--differing only by syntax--is great.

>CONCLUSION
>Personally I would prefer to see a syntax for URIs that copes with both
>QNames and URIs in the same attribute--it's what I'd hoped when I first
>started work on RDF/A, and is in effect what N3 does. Then it ceases to be
>the responsibility of the mark-up, and moves to the realm of the attribute
>processing.

>Regards,

>Mark

>Mark Birbeck
>CEO
>x-port.net Ltd.

>e: Mark.Birb...@x-port.net
>t: +44 (0) 20 7689 9232
>w: http://www.formsPlayer.com/
>b: http://internet-apps.blogspot.com/

>Download our XForms processor from
>http://www.formsPlayer.com/

>> -----Original Message-----
>> From: www-html-requ...@w3.org
>> [mailto:www-html-requ...@w3.org] On Behalf Of Al Gilman
>> Sent: 08 June 2005 14:59
>> To: Misha Wolf; dc-gene...@jiscmail.ac.uk
>> Cc: www-rdf-inter...@w3.org; semantic-...@w3.org;
>> www-h...@w3.org; iptc-metad...@yahoogroups.com
>> Subject: Re: DC in XHTML2

>> At 6:04 PM +0100 6/7/05, Misha Wolf wrote:

>> >Is anyone else in the DC community looking at the use of DC in
>> >XHTML2 and thinking along similar lines to us? We would be
>> very happy
>> >to work with others on this issue.

>> It sounds as though you could use @property with the same
>> sort of intermediate dictionary that we think we can do for
>> extensions to the repertory of values for @role.

>> Here (If I have it straight) we will have a role dictionary
>> (separate URI from the XHTML 2.0 namespace or the current
>> document instance) which has a named entry which gathers a
>> collection of assertions and then a qualified name referring
>> to this named entry in the dictionary will assert those
>> assertions about the element bearing that QName as a value of @role.

>> In the process of developing this we will definitely need
>> assistance from SW [Best Practices?] and would be delighted
>> to compare notes with "the people who brought you NewsML."

>> Keep in touch with Lisa or post progress updates or questions
>> to <wai-xt...@w3.org> for public discussion and
>> <w3c-wai...@w3.org> if W3C member-confidential for any reason.

>> Al

>> >As some of you will know, the XHTML2 draft [1] introduces a very
>> >interesting syntax for RDF, which many would consider to be an
>> >improvement on the traditional RDF/XML syntax. No doubt,
>> many content
>> >authors will be seeking to add DC metadata to their XHTML2 content
>> >using these new mechanisms.

>> >The News Architecture Working Party of the International Press
>> >Telecommunications Council (IPTC) is investigating the use of
>> >XHTML2 for expressing DC and other metadata. A major
>> problem for us is
>> >the lack of support in the current XHTML2 draft (as in
>> RDF/XML) for the
>> >use of QNames to express terms in controlled vocabularies
>> (aka values
>> >of properties).

>> >At the moment, the XHTML2 @content attribute takes PCDATA
>> and the @href
>> >attribute takes IRIs. There is no attribute available for QNames.

>> >We want to be able to use, eg, <dc:subject> with a QName as
>> a value (ie
>> >the object of the RDF statement). The reasons include
>> legibility and
>> >compactness. News items (and news headlines) often carry numerous
> > >subject codes, hence the need for compactness.

>> >Is anyone else in the DC community looking at the use of DC in
>> >XHTML2 and thinking along similar lines to us? We would be
>> very happy
>> >to work with others on this issue.

>> >[1] http://www.w3.org/TR/xhtml2

>> >Misha Wolf
>> >Standards Manager, Reuters
>> >Chair, News Metadata Framework WG, IPTC Vice-Chair, News
>> Architecture
>> >WP, IPTC

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