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LC-216 merge mixed, textOnly, and string?

From: C. M. Sperberg-McQueen <cmsmcq@acm.org>
Date: Thu, 05 Oct 2000 23:56:41 -0600
Message-Id: <>
To: "Martin J. Duerst" <duerst@w3.org>, Misha Wolf <misha.wolf@reuters.com>
Cc: W3C XML Schema Comments list <www-xml-schema-comments@w3.org>
Dear Martin and Misha:

The W3C XML Schema Working Group has spent the last several months
working through the comments received from the public on the last-call
draft of the XML Schema specification.  We thank you for the comments
you made on our specification during our last-call comment period, and
want to make sure you know that all comments received during the
last-call comment period have been recorded in our last-call issues
list (http://www.w3.org/2000/05/12-xmlschema-lcissues).

Among other issues, you raised the point registered as issue LC-216,
which suggests that XML Schema abolish, in effect, the use of the
simple type String and the textOnly complex type for elements.  The
effect would be that all elements which are not empty or of some
non-String simple type would be of complex type 'mixed'; this would
make it easier to add extra child elements (such as bidi elements) to
content models thought of by the schema author as 'just characters'.

The WG discussed the issue at some length. We understand your goal,
and we agree that there is some danger that some schema authors will
use 'string' where they ought to use mixed content.  But we were
unable to agree with you that your proposal represented the correct
solution to this problem.

Best-practice guidelines might go far to minimize the problems
foreseen. We cannot wholly eliminate those problems, because it is
necessary to provide the existing functionality for the cases where it
is what is actually intended -- i.e. where the schema author used
String because String was what was intended.  We need, that is, to
provide enough rope to allow the schema author to do the job; it
follows that schema authors will have enough rope to hang themselves,
and this is, we believe, unavoidable.  Forcing all application
software always to be prepared for subelements, and never allowing it
to expect only strings, simply transfers the burden from one set of
shoulders to another. Instead of making hard things easy, this
proposal would end up making simple things hard.

Some WG members also suggested that the proposal would do too much
violence to our type system: mixed-content elements do not have
children of the String simple datatype, just characters.  We are
unable to agree, therefore, with your suggestion that your proposal
would cause no problems at all.

It would be helpful to us to know whether you are satisfied with the
decision taken by the WG on this issue, or wish your dissent from the
WG's decision to be recorded for consideration by the Director of
the W3C.

with best regards,

-C. M. Sperberg-McQueen
  World Wide Web Consortium
  Co-chair, W3C XML Schema WG
Received on Thursday, 5 October 2000 21:49:54 UTC

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