W3C home > Mailing lists > Public > public-grddl-wg@w3.org > April 2007

RE: hGRRDL for hCard: test case of a GRDDL transformation to produce RDFa from hCards

From: Clark, John <CLARKJ2@ccf.org>
Date: Fri, 20 Apr 2007 09:51:20 -0400
Message-ID: <F122C25B4CD6F34BB119A97593679601027CA860@CCHSCLEXMB59.cc.ad.cchs.net>
To: "Jeremy Carroll" <jjc@hpl.hp.com>, "Shane McCarron" <shane@aptest.com>
cc: "Ben Adida" <ben@adida.net>, "Fabien Gandon" <Fabien.Gandon@sophia.inria.fr>, "GRDDL Working Group" <public-grddl-wg@w3.org>, public-rdf-in-xhtml-tf@w3.org

> The spec is written only for valid xhtml, and that seems 
> appropriate, but the expectation is that implementations do 
> the right thing with invalid xhtml.

I suppose by "valid", here, we mean "valid with respect to a declared
DTD" as defined in the XML Recommendation[0], and that further this DTD
must be one defined in "one of" the XHTML Recommendations.  If, however,
we could take a step back from that particular precipice, I would find
it far more interesting to think of validity in terms that James Clark
recently used[1]:

  Validity should be treated not as a property of a document
  but as a relationship between a document and a schema.

I think it's useful for the GRDDL spec to talk about "valid" XHTML, as
long as it also provides an appropriate schema that supports GRDDL's
fundamental purpose.  Consider, for example:

<schema language="RelaxNG Compact Syntax">
default namespace = "http://www.w3.org/1999/xhtml"

start = element html
  element head { any },
  element body { any }

anyElement = element * { any* }

any = (attribute * {text} | text | anyElement)*

This would basically say that a valid XHTML document, for GRDDL
purposes, is any document in the XHTML namespace having (at least) a
very skeletal XHTML structure.  This obviously would include many
documents that are not valid against a published XHTML DTD, but so what?
What harm does that do?  If users mix in bits of other languages, should
we care?  Would it affect GRDDL processing on an "XHTML" document?

Importantly, such a schema would validate any document that would also
validate using the first approach, above, while treating XHTML as more
of an envelope than a complete format.  It would be an external
relationship applied by the GRDDL spec meant to be useful only to a
GRDDL-aware agent for providing a (very) rudimentary awareness of XHTML.

Take care,

    John L. Clark

[0] http://www.w3.org/TR/2006/REC-xml-20060816/#dt-valid


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Received on Friday, 20 April 2007 13:51:22 UTC

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