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Re: Is XHTML 1.0 2nd ed. Section 4.3 really informative?

From: ITO Tsuyoshi <tsuyoshi@is.s.u-tokyo.ac.jp>
Date: Sun, 13 Jan 2002 17:08:01 +0900 (JST)
Message-Id: <20020113.170801.65657214.tsuyoshi@is.s.u-tokyo.ac.jp>
To: hammond@csc.albany.edu
Cc: www-html@w3.org
From: hammond@csc.albany.edu (William F. Hammond)
Date: 08 Jan 2002 09:29:52 -0500
Message-Id: <i7sn9g29wf.fsf@pluto.math.albany.edu>

>    Definition: Each XML document contains one or more elements, the
>    boundaries of which are either delimited by start-tags and end-tags,
>    or, for empty elements, by an empty-element tag

``Empty elements'' are different from elements declared EMPTY.  The
former simply means elements with no content.  ``<span></span>'' is an
example of an empty element.  The elements declared EMPTY must be
empty, but the reverse is not always true.  Please see Section 3.1 of
XML specification:
  <http://www.w3.org/TR/2000/REC-xml-20001006#NT-content>

And it does not say that you must always use an empty-element tag for
an empty element.  You can use both ``<span></span>'' and ``<span/>''
as long as XML validity is concerned.
  <http://www.w3.org/TR/2000/REC-xml-20001006#NT-EmptyElemTag>

> Please understand: the thrust of this recommendation is that one
> should not write <foo></foo> when an element is defined-empty.

The fact that XHTML is an XML application implies that a Strictly
Conforming XHTML Document must be a valid XML document under one of
the XHTML DTDs.  This is not the matter of ``should write'' or
``should not write'' .  XML specification allows ``<br></br>'' to
appear in valid XML documents even if ``br'' element is defined EMPTY.
It only recommends not to use such representations if you want
interoperability.

In addition, we were talking about empty-element tags for elements
other than those declared EMPTY, such as ``<span />'' , not about the
pair of start and end tags for elements declared EMPTY, such as
``<br></br>'' .

Last Wednesday one member of HTML Working Group suddenly notified me
that HTML WG agreed that the wording in Section 4.3 was confusing.  It
seems that they were discussing this issue on their member-only
mailing list, whose archive is not publicly accessible.  I do not know
when they began discussing this or how they came to the conclusion.
He also told me that they would change the wording in Section 4.3; I
am glad to hear it anyway.

Best regards,
-- ITO Tsuyoshi  <tsuyoshi@is.s.u-tokyo.ac.jp> --
-- Department of Information Science           --
--                  in the University of Tokyo --
Received on Sunday, 13 January 2002 03:08:14 GMT

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