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XML Core WG comment on Pointer Methods in RDF

From: Grosso, Paul <pgrosso@ptc.com>
Date: Fri, 10 Apr 2009 10:44:30 -0400
Message-ID: <CF83BAA719FD2C439D25CBB1C9D1D3020F2F1FED@HQ-MAIL4.ptcnet.ptc.com>
To: <public-wai-ert@w3.org>
Cc: <public-xml-core-wg@w3.org>
The XML Core WG has reviewed "Pointer Methods in RDF":
http://www.w3.org/TR/2009/WD-Pointers-in-RDF-20090310/

On the whole, the pointer framework described by this document seems
to be well thought out. There are two areas on which the XML Core WG
wishes to provide feedback.

The WD defines an element (an RDF property actually, but one that's 
serialized as an element) named "ptr:XMLNamespace".  Per the XML 
Recommendation [1]:

 Names beginning with the string "xml", or with any string which
 would match (('X'|'x') ('M'|'m') ('L'|'l')), are reserved for
 standardization in this or future versions of this specification.

Since, using a default namespace, it is always (at least theoretically)
possible that a local name may appear without a prefix, the name
"ptr:XMLNamespace" does violate that above statement in the XML spec.

We would ask that the ERT WG consider using a different name that
avoids this issue.

The second point is of more substantial technical import.
Although the Pointer Methods spec discusses pointing into XML as 
one of the use cases, many of the pointers provided by the spec 
operate (or appear to operate) on the character serialization of 
the resource.  But when accessing an XML document as an XML 
document (and not as merely a text-based resource), one is really
accessing the XML Infoset [2], and character or byte based pointing
mechanisms do not make sense.

For example, it's not clear what meaning one could associate with 
a pointer range that started in the beginning of an end tag and 
ended in the middle of an attribute name on some following start tag. 
It is not even coherent to assert the existence of such a range 
in an XML document.

Perahps the answer is as simple as saying "don't use line/char, char
offset, byte snippet, etc. pointers when pointing into XML documents"
but we believe the Pointer Methods spec does need to address this issue.

paul

Paul Grosso for the XML Core WG


[1] http://www.w3.org/TR/xml/#dt-name
[2] http://www.w3.org/TR/xml-infoset/
Received on Friday, 10 April 2009 14:46:05 GMT

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