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

Re: [RDFa] ISSUE-3 @class and @role for rdf:type

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Wed, 18 Jul 2007 17:09:26 +0100
Message-ID: <640dd5060707180909k4d8ca48pa84f0e272b3dd833@mail.gmail.com>
To: "Niklas Lindström" <lindstream@gmail.com>
Cc: "Ben Adida" <ben@adida.net>, public-rdf-in-xhtml-tf@w3.org

Fantastic. :)

On 18/07/07, Niklas Lindström <lindstream@gmail.com> wrote:
> Hi Mark!
>
> This is a late reply (I have caught up now ;)) mostly for closure.
> Thank you for your comments; I believe your interpretation of my
> thoughts were to the point. I'm glad to see agreement overall about
> this issue. Using @class can still be done in a completely controlled
> fashion if hGRDDL is pursued further (which I hope, it seems really
> feasible).
>
> It is interesting to reflect about these "chimeric" aspects of RDFa
> you mention. It is the strength of the application, but as we see in
> the ongoing debates, because of this nature, we have to be thorough,
> formulate simple (enough) rules and seek out edge cases to avoid
> complicating matters. (Which I think is the case, so I'm happy.)
>
> I see two somewhat different uses for RDFa. One is the general "pieces
> of data" case, where you expose e.g. personal, publication and similar
> data within a more loosely typed web page setting. The other is the
> "enhanced document" case, where the document and its component parts
> are the primary subjects about which to add precision to "expose
> relevance" to the Semantic Web "view of the world". (Both cases being
> somewhere between "rich text" and "data record".)
>
> The latter is what I and my colleagues have been (successfully so far)
> using RDFa for, to structure legal documents for the intent of
> creating a unified approach to swedish legal information (as
> commissioned by Verva, the Swedish Administrative Development Agency).
> This is a work which is now rounding up a prototyping and initial
> trial period, and which I hope to make a more general write-up about
> later this year. It has been the primary origin for my thoughts and
> posts here.
>
> I have used a metaphor in describing RDFa where you "use colored pens
> to add precision to the content". It's great when each color is unique
> to the point of being a URI. ;)
>
> Best regards,
> Niklas
>
>
>
> On 7/9/07, Mark Birbeck <mark.birbeck@x-port.net> wrote:
> > Hi Niklas,
> >
> > Very useful comments, many thanks. I hope you don't mind if I just
> > reply to a couple of points that particularly caught my eye, in
> > particular the following:
> >
> > > [snip]
> > >
> > > But the issue for me is that the usage of @role, as far as I can
> > > interpret it, is to define a relation to a resource *with the subject
> > > being the element itself*. If this is the case, @role is out.
> >
> > and:
> >
> > > [snip]
> > >
> > > One practical reason is that @class seems today to be about attaching
> > > information about the element itself (akin to how I interpret @role
> > > above). It may not be entirely clear, but considering a designer
> > > aiming to state some stuff about a div containing a name and phone
> > > number, '<div class="person">' is perhaps best interpreted as "this
> > > element is a person data container".
> >
> > This is a very interesting point. Along very similar lines, Ben
> > mentioned a while back that one of the things that TBL didn't like
> > about the use of @class in RDFa was that he felt that when he uses
> > @class in his documents, he is actually saying something about the
> > document element itself, and not the 'Person' or 'Event' being alluded
> > to. Your comments seem to me to be referring to exactly this issue.
> >
> > The compromise we made with TBL's comments was to say that only
> > prefixed values in @class should be parsed by an RDFa parser, but in a
> > way that is worse than parsing all values. This is because--if we use
> > the ideas you're referring to here--we now have one range of @class
> > values that are in reference to elements in the document, and another
> > range of @class values that apply to meta-information. In other words
> > we've made the attribute have two different meanings based on its
> > value, which is not good.
> >
> > At the risk of seeming to be dealing with angels jumping up and down
> > on pin-heads, I'll venture to put this issue into its RDF context.
> >
> > If we think first of RDF/XML, it is not actually possible in RDF/XML
> > to say anything about the document that carries the RDF/XML. So if you
> > have (to continue with an earlier example...sorry Ivan!):
> >
> >   <http://blah.blah/ivan.rdf>
> >
> > any statement you ever make using that URI will always be about the
> > resource Ivan, and never about the XML document itself.
> >
> > Now, you could say that RDFa has gone somewhat in that direction,
> > although not quite as far.
> >
> > As you rightly allude to Niklas, the way we have things at the moment
> > in RDFa is that, whilst statements are 'carried' by an HTML/XHTML
> > document, they are not generally _about_ the document itself--they are
> > usually about 'People' and 'Events' which are being referred to by the
> > document.
> >
> > However, unlike an RDF/XML document, with RDFa it *is* possible to
> > make statements about the document itself. RDFa gives us a chimera; it
> > can be both a web document (an information resource in RDF parlance)
> > and at the same time it can carry metadata about resources (equivalent
> > to the RDF/XML side).
> >
> > You rightly draw attention to @role; that's a very good illustration
> > of how we fully intended to maintain this distinction. @role was
> > always meant to be about the ability to say things like "the purpose
> > of this script element is to provide a hint to a user"; as you say,
> > that's saying something about an element in a document, and is very
> > different from saying things like "some external document is a
> > license".
> >
> >
> > So although I think we do need an RDFa 'view' on what @class and @role
> > do, I think we're not really in a position to say quite what it should
> > be at the moment; should these attributes only provide metadata about
> > the information that our HTML document is 'carrying' or should they
> > provide information about the document itself, in the way that @role
> > was originally intended? We've been quite careful in other places to
> > watch what we do with @id, for example, and I think your comments are
> > a useful reminder that we should continue to take care that we don't
> > close for the future the ability to say useful things about the
> > document itself.
> >
> >
> > > 3. Regarding a new attribute. Not remembering all suggestions, I
> > > suggest "@instanceof" - not the least since the rdfs:comment of
> > > rdf:type states "The subject is an instance of a class". Meshed
> > > example:
> > >
> > >     <div about="#jane" class="person" instanceof="foaf:Person">
> > >         <span class="fn" property="vcard:fn">Jane Doe</span>
> > >     </div>
> >
> > That's about the best suggestion so far, I think. :)
> >
> > Regards,
> >
> > Mark
> >
> > --
> >   Mark Birbeck, formsPlayer
> >
> >   mark.birbeck@x-port.net | +44 (0) 20 7689 9232
> >   http://www.formsPlayer.com | http://internet-apps.blogspot.com
> >
> >   standards. innovation.
> >
>
>


-- 
  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 Wednesday, 18 July 2007 16:09:35 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 8 January 2008 14:15:08 GMT