W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > April 2007

Re: CLASS and ROLE

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Tue, 17 Apr 2007 13:57:07 +0100
Message-ID: <640dd5060704170557s17a30954yfd4296ec2486f142@mail.gmail.com>
To: "Ben Adida" <ben@adida.net>
Cc: "José Manuel Cantera Fonseca" <jmcf@tid.es>, RDFa <public-rdf-in-xhtml-tf@w3.org>

Hi Jose,

Just one other thing to add to Ben's comments; the role attribute is
actually aimed at a much broader set of use cases than accessibility.
It was devised quite a few years ago, as a basic semantic hook, and is
already being used in server-side processing of mobile documents,
accessibility, and of course RDFa.

Best regards,

Mark

On 17/04/07, Ben Adida <ben@adida.net> wrote:
>
>
> Jose,
>
> Thanks for your input! Let me attempt to clear up a few things first,
> and then see if we can get to the root of your objection.
>
> In fact, the CLASS attribute is not meant solely for presentational
> purposes. Note the HTML4 spec [1], which indicates that CLASS is also
> meant for general user-agent processing. Even in the presentation use
> case, the CLASS *should* designate a semantic role for the element, e.g.
> class="menubar", and then the stylesheet indicates how to perform the
> presentation for that semantically designated portion of the page.
>
> In other words, we are not really bowing to browser vendor pressure
> here, we're simply saying that CLASS has always been about semantics, so
> let's make sure that is reflected in the RDF triples we produce, and the
> clearly relevant predicate is rdf:type.
>
> In the case of the ROLE attribute, all we're doing is outputting an
> xh:role predicate that corresponds exactly to the ROLE attribute placed
> on the element. We think that maps exactly to the accessibility case,
> and our brief interactions so far with the WAI group seem to confirm
> this, though I hope they will chime in if that's not the case!
>
> To sum things up: with RDFa, we've always tried to use existing HTML
> attributes where these attributes *already* have semantic connotation.
> REL and REV obviously fit the description, and I'm guessing you don't
> object to their use for RDFa? We believe CLASS fits in the same
> category. We're still discussing how UL, OL, and LI may have RDF list
> semantics, though that is still very much in flux. I hope the above
> helps make our reasoning clearer.
>
> So, getting back to your objection: is there a use case you're worried
> about? Or a piece of markup you think would yield a "bad" set of
> triples? I want to dig a bit deeper, because if we adopt the principle
> that we must only use new attributes, then we will be missing out on
> existing HTML semantics, and a number of natural RDFa examples, in
> particular the ones that use the REL attribute, would have to go away by
> the same principle.
>
> -Ben
>
>
> [1] http://www.w3.org/TR/html401/struct/global.html#h-7.5.2
>
>
> José Manuel Cantera Fonseca wrote:
> >  Dear members of the RDF-A group,
> >
> > My name is Jose Cantera, I'm with Telefonica and  I represent Telefonica
> > in some W3C groups. I'm writing this e-mail to express our strong
> > disagreement with respect to the usage of the class attribute in RDF/A.
> > The class attribute has presentational connotations but not semantic
> > connotations. You are mixing things in a very dangerous and confusing
> > manner.
> >
> > We think it's a big mistake you are making. *New attributes are needed
> > for expressing the semantics* and not reusing existing ones that
> > initially were intended to other purposes. Semantic-annotation
> > attributes should be different than other attributes and should easily
> > be distinguished from the other.
> >
> > Regarding the role attribute the same comment applies. Role attribute
> > has connotations related to accessibility but not to semantics. New
> > attributes for semantics are needed, although we know that you are, as
> > usual, adopting the ideas of browser vendors who are not willing to
> > create or consider new attributes in HTML-like languages.
> >
> > This issue, for us is a big issue, and somehow would "limit and stop"
> > our adoption of RDF-A in our research work.
> >
> > Kind regards
> >
> > Ben Adida escribió:
> >> Hi all,
> >>
> >> Though we have discussed the CLASS and ROLE issue, we haven't quite
> >> resolved the last consensus we came to. So, I want to phrase the
> >> consensus as best as I understand it. We will vote to resolve this (or a
> >> modified version if need be) at next week's telecon on 4/23, so please
> >> send all comments ASAP.
> >>
> >> Proposed Resolution:
> >>
> >> In all RDFa-compliant HTML documents (e.g. XHTML1.1+RDFa), the CLASS
> >> attribute is of type CURIEs, a space-separated list of values. Each
> >> qualified CURIE value yields an rdf:type assertion on the subject
> >> corresponding to the attribute's element, exactly as if the element had
> >> a child LINK element. Unqualified CURIEs are ignored, e.g. class="foo".
> >>
> >> e.g.
> >>
> >> <div id="foo" class="big foaf:Person">
> >> ...
> >> </div>
> >>
> >> yields
> >>
> >> <#foo> rdf:type foaf:Person .
> >>
> >>
> >> Where the ROLE attribute is defined, e.g. XHTML2, its value is also
> >> CURIEs, thought this time it yields an xh2:role assertion (with xh2 the
> >> XHTML2 namespace). The subject resolution is identical to that of the
> >> CLASS attribute. As there is no "backwards compatibility" issue with
> >> this attribute, all values yield triples
> >>
> >> e.g.
> >>
> >> <div role="wai:Menu nav">
> >> ...
> >> </div>
> >>
> >> yields
> >>
> >> _:div0 xh2:role wai:Menu .
> >> _:div0 xh2:role :nav .
> >>
> >>
> >> -Ben
> >>
> >>
> >>
> >
>
>
>
>


-- 
  Mark Birbeck, formsPlayer

  mark.birbeck@x-port.net | +44 (0) 20 7689 9232
  http://www.formsPlayer.com | http://internet-apps.blogspot.com

  standards. innovation.
Received on Tuesday, 17 April 2007 12:57:11 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 8 January 2008 14:15:04 GMT