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[closed] xmlsch-11 layering on xml

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 29 Apr 2003 20:05:09 +0100
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: W3C XML Schema IG <w3c-xml-schema-ig@w3.org>, www-rdf-comments@w3.org
Message-ID: <22326.1051643109@hoth.ilrt.bris.ac.uk>


Dear Colleagues

The RDF Core WG has considered your last call comment captured in

   http://www.w3.org/2001/sw/RDFCore/20030123-issues/#xmlsch-11

(raised in section
 "4.4. Normative specification of XML grammar (policy, substantive)" of
http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0489.html )

The main points you raised in this comment are:

1) RDF/XML is defined in "what is very nearly a character-level BNF
  [which] is at best a missed opportunity and at worst a serious
  mistake." 
    - obscuring important parts of the document type
    - making it very difficult for the reader to actually
      understand what is and isn't actually allowed.
    - confusing layers

RDF/XML is entirely layered on the XML Infoset as defined in
  Syntax Data Model
  http://www.w3.org/TR/rdf-syntax-grammar/#section-Data-Model
and is not defined at the character-level.

All XML detail is handled by the XML specifications, not this
document - deployed RDF/XML applications are entirely built on
standard XML tools.  In layering on the XML infoset, we leave only
the important parts of RDF/XML that users and application writers
need be concerned about - elements, attributes, whitespace and text.

It would have been a mistake to gloss over where, say, the whitespace
was significant and where it was ignored - which was one problem with
the original RDF M&S specification.


2) Rules out XML documents not parsed from character streams (such as DOM)

This was explicitly called out:
  [[
    This model illustrates one way to create a representation of an
    RDF Graph from an RDF/XML document. It does not mandate any
    implementation method - any other method that results in a
    representation of the same RDF Graph may be used.

    In particular:
    ...
	* This specification does not require the use of [XPATH] or [SAX2]
  ]]
  http://www.w3.org/TR/rdf-syntax-grammar/#section-Data-Model

If a DOM interface can provide the very few (4) XML Infoset Infoitems
that are needed here, it is not ruled out.


3) Suggests a two-step approach first mapping to canonical RDF form
   constrained by DTD or XML Schema

An approach using a mapping to a canonical RDF written in XML is
related to issue xmslch-10 where we explain why we didn't feel we
could do this under the current charter.  It certainly would have
been useful and helped.

The model and grammar used here closely matches how many RDF/XML apps
were written, in a token matching style that can be used with
standard syntax lexers and grammar generators.  This approach has
proved suitable after other implementor feedback.



The RDF Core Working Group has decided:

    http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Apr/0361.html

that the explanation above answers your comment as a clarification.

Please reply to this email, copying www-rdf-comments@w3.org indicating
whether this decision is acceptable.

Thanks

Dave
Received on Tuesday, 29 April 2003 15:08:06 GMT

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