Re: Proposal for an additional 'link type' for rdf:type

Hi Ivan,

Thanks for forcing me to think it through more. :) I think that there
is probably a neat way to write this using current mark-up, although
working through it has highlighted something that I think we need to
clarify.

Sticking purely with trying to make the rdf:type use-case easier
(i.e., rather than the general use of RDF/RDFS namespaces), there is
nothing to stop us doing this:

  <html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:foaf="http://xmlns.com/foaf/0.1/"
  >
    <head>
      <title>My profile</title>
      <link about="" instanceof="[foaf:PersonalProfileDocument]" />
    </head>
     .
     .
     .
  </html>

It looks odd, since there is no @rel or @rev, but it is allowed by the
syntax. But once you go down that route, you might as well use the
following, which is also allowed by the syntax, and is probably much
clearer in terms of intent:

  <html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:foaf="http://xmlns.com/foaf/0.1/"
  >
    <head about="" instanceof="[foaf:PersonalProfileDocument]">
      <title>My profile</title>
    </head>
     .
     .
     .
  </html>

Which brings us to the point that I think we need to clarify; what if
I wrote this:

    <head instanceof="[foaf:PersonalProfileDocument]">
      <title>My profile</title>
      <meta property="dc:creator" content="John Doe" />
    </head>

In our current rules this would generate a new bnode for <head>, and
the dc:creator property would apply to that, which I don't think is
desirable. But if we were to make it a little more explicit that the
'identity' of <head> is the current document, unless overridden
*explicitly* by @about, then my rdf:type use-case falls out quite
neatly to the following mark-up:

  <html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:foaf="http://xmlns.com/foaf/0.1/"
  >
    <head instanceof="[foaf:PersonalProfileDocument]">
      <title>My profile</title>
    </head>
      .
      .
     .
  </html>

I think that's actually quite clear from the point of view of what an
author is trying to do, and it has also exposed that we might need to
say a little more about what happens with the <head> element.

What do you think?

Regards,

Mark



On 01/10/2007, Ivan Herman <ivan@w3.org> wrote:
> Hm. You won't like me, but I am not sure I like it:-)
>
> Though is see the rationale, we create some sort of an odd case. At the
> moment the agreement is that a @rel value without a CURIE prefix is
> considered to be in
>
> http://www.w3.org/1999/xhtml/vocab#
>
> and that is it. This is a very clear and easy-to-follow rule. What you
> propose is that, well, this is true, _except_ for the value of
> instanceof that behaves differently. I am not sure it is good if we
> begin to introduce such exceptions.
>
> Or did I misunderstand you?
>
> A possible way out is to say that the 'rdf:' prefix (and probably the
> 'rdfs:' prefix) will always be added to the result of an RDFa processor
> with the usual values. This is not very nice either, but I would prefer
> to solve your problem that way...
>
>
> Ivan
>
> Mark Birbeck wrote:
> > Hello all,
> >
> > Whilst considering RDFa use in the wild, it occurred to me that
> > constructs like the following would almost certainly become quite
> > common:
> >
> >   <html
> >    xmlns="http://www.w3.org/1999/xhtml"
> >    xmlns:foaf="http://xmlns.com/foaf/0.1/"
> >    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> >   >
> >     <head>
> >       <title>My profile</title>
> >       <link rel="rdf:type" resource="[foaf:PersonalProfileDocument]" />
> >     </head>
> >     .
> >     .
> >     .
> >   </html>
> >
> > If the author wants to avoid having to include the RDF namespace, they
> > would have to change their mark-up to look something like this:
> >
> >   <html
> >    xmlns="http://www.w3.org/1999/xhtml"
> >    xmlns:foaf="http://xmlns.com/foaf/0.1/"
> >   >
> >     <head>
> >       <title>My profile</title>
> >     </head>
> >     <body about="" instanceof="foaf:PersonalProfileDocument">
> >       .
> >       .
> >       .
> >     </body>
> >   </html>
> >
> > However, if we added an additional link type, such as 'a' or
> > 'instanceof', we could also allow the following mark-up:
> >
> >   <html
> >    xmlns="http://www.w3.org/1999/xhtml"
> >    xmlns:foaf="http://xmlns.com/foaf/0.1/"
> >   >
> >     <head>
> >       <title>My profile</title>
> >       <link rel="instanceof" resource="[foaf:PersonalProfileDocument]" />
> >     </head>
> >     .
> >     .
> >     .
> >   </html>
> >
> > This avoids the need to declare the RDF namespace, and keeps the
> > metadata in the head of the document which seems more appropriate for
> > this particular kind of statement.
> >
> > Regards,
> >
> > Mark
> >
> >
>
> --
>
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>


-- 
  Mark Birbeck, formsPlayer

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

  standards. innovation.

Received on Monday, 1 October 2007 12:11:51 UTC