Pete,
Some comments and clarification to this discussion from the Semantic Web
community perspective.
1. There is a set of strong voices in the current development around
HTML (commonly referred to as HTML5) that try to dismiss the usage of
profiles for HTML. Personally I think it is a mistake, but the major
argument is that, until now, that attribute has not been used. I think
your usage of the profile attribute _is_ the right choice, but I thought
I should bring this to your attention.
To be more proactive: I think the DCMI community should clearly raise
its voice on the appropriate fora requiring that the profile attribute
should _not_ be removed. This is a large, well, potentially huge:-)
community, and its voice should be heard.
(I will certainly forward your mail to the W3C staff contact for
information. But the voice of a community is to be taken much more
seriously).
2. I have some comments and clarification on the RDFa issues below, but
I mixed it with your questions. I hope those are helpful.
Pete Johnston wrote:
>
> DC-HTML & RDFa
> ==============
>
> What this new draft _doesn't_ address is any RDFa [4] interpretation of
> an XHTML 1.0/1.1 doc using this profile.
>
> I must admit I'm still a bit unclear about how RDFa applies to XHTML
> 1.0/1.1 docs. But my understanding (and I could be wrong about this!) is
> that RDFa will not be defined as an X/HTML metadata profile, so there
> will not be a profile URI for RDFa.
This is not yet decided, and the RDFa group is still discussing it.
There are serious arguments to define such profile.
> However - at least in XHTML 1.1 -
> there will be some other "hook"/"trigger" to signal that an XHTML 1.1
> doc contains RDFa - a reference to a specific DTD in the DocType
> declaration, I think?
>
Yes, a specific DTD is in development right now. But, as I said, this
issue is not yet decided.
> If I'm wrong about that, and if an RDFa processor _is_ going to extract
> triples from an XHTML 1.0/1.1 doc regardless, then, given that RDFa uses
> a QName-like convention based on XML Namespaces for representing URIs,
> and this profile (and eRDF) uses a different convention, I'd expect an
> RDFa processor to generate some rather nonsensical triples e.g. given
>
> <meta name="dc.title" content="My title" />
> <link rel="dc.creator" href="http://example.org/Fred" />
> <link rel="schema.dc" href="http://purl.org/dc/elements/1.1/" />
>
> a GRDDL processor using the dc-html profile transform would generate
>
> <> dc:title "My title" .
> <> dc:creator <http://example.org/Fred> .
>
> but an RDFa processor would generate (I think?)
>
> <> <http://www.w3.org/1999/xhtmldc.creator> <http://example.org/Fred> .
> <> <http://www.w3.org/1999/xhtmlschema.dc>
> <http://purl.org/dc/elements/1.1/> .
>
In the present situation that is indeed correct:-( I will forward your
questions/comments to the RDFa group on this.
> (I think the meta element would be ignored because RDFa uses a different
> attribute for the predicate URI.)
>
I presume you refer to the 'name' attribute in the <meta> element. Yes,
at the moment, the 'property' attribute is used (with 'content'). Again,
I will forward this issue to the RDFa community.
> But I'm hoping that my concern here is without foundation, and an RDFa
> processor _does_ need some hook before it goes to work on an XHTML
> 1.0/1.1 doc, and so it will _not_ generate those spurious triples.
>
Hm. I am not sure the two are so clearly related. On the one hand, one
of the issue is whether an HTML file is processed via an RDFa processor
or not. But even if yes, there are some syntactic differences. The 'a.b'
notation for a dublin core term is indeed not recognized by the current
RDFa spec, regardless of the other issue.
> But I suppose this begs the larger question of whether DCMI should
> recommend shifting from this current approach (an X/HTML metadata
> profile compatible with the eRDF profile and accessible to a GRDDL
> processor) to an explicitly RDFa-based approach.
>
> Given that RDFa is still under development at this point in time, I'm
> hesitant to recommend that change right now, and I think there is
> considerable value in a GRDDL-able profile.
>
Just to make it clear how an RDFa-type profile would look like (I
randomly picked example 9 from your document)
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
profile="http://dublincore.org/documents/2007/07/27/dc-html/"
xmlns:dcterms="http://purl.org/dc/terms/">
<head>
<title>Services to Government</title>
<link rel="schema.DCTERMS" href="http://purl.org/dc/terms/" />
<meta property="dcterms:title" content="Services to Government" />
<link rel="dcterms:subject" href="http://example.org/topics/archives"
title="Archives" />
</head>
<body>
</body>
</html>
Ie, the difference is using ':' in the <link> and <meta> elements, using
the @property instead of the @name, and using a namespace declaration
instead of the <link rel="schema.DCTERMS".
I wonder whether this would be a major shift for DCMI; I cannot judge
that. Note that it is absolutely no problem adapting a GRDDL script to
follow this RDFa syntax, so I am not sure that argument is justified.
> But at some point in the future once RDFa is done, it may be worth
> producing a separate note on encoding DC metadata using RDFa.
>
Another possibility is to propose a syntax that is upright compatible
with RDFa; this can be easily used and adapted with GRDDL...
I hope this helps. I will also forward your mail to some other people at
W3C to help moving things forward.
Sincerely
Ivan
> Anyway, comments on any aspect of this welcome - though I'm on leave for
> a week, so I won't be replying for a few days ;-)
>
> Cheers
>
> Pete
>
> [1] http://dublincore.org/documents/dcq-html/
> [2] http://www.w3.org/TR/REC-html40/struct/global.html#profiles
> [3] http://www.w3.org/TR/2007/PR-grddl-20070716/
> [4] http://www.w3.org/TR/2007/WD-xhtml-rdfa-primer-20070312/
>
>
> ---
> Pete Johnston
> Technical Researcher, Eduserv Foundation
> Web: http://www.eduserv.org.uk/foundation/people/petejohnston/
> Weblog: http://efoundations.typepad.com/efoundations/
> Email: [log in to unmask]
> Tel: +44 (0)1225 474323
--
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
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