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Re: Action item on the virtues of error-handling

From: Masayasu Ishikawa <mimasa@w3.org>
Date: Wed, 22 Oct 2003 16:07:16 +0900 (JST)
Message-Id: <20031022.160716.78702706.mimasa@w3.org>
To: www-tag@w3.org

> On Tue, 2003-10-21 at 22:11, Tim Bray wrote:
> > Also, HTML specifies "must-ignore" processor for 
> > user-agents that encounter markup that is not part of HTML.

Dan Connolly <connolly@w3.org> wrote:
> Actually, it doesn't. The spec acknowledges that some software
> does this, but doesn't mandate it in any way.

Dan is right.  The HTML 4 specification states in "4.1 Definitions" [1],
under "Error conditions", as follows:

  This specification does not define how conforming user agents handle
  general error conditions, including how user agents behave when they
  encounter elements, attributes, attribute values, or entities not
  specified in this document. 

  However, for recommended error handling behavior, please consult
  the notes on invalid documents.

Appendix B.1 "Notes on invalid documents" [2] is non-normative, and
it says "should", not "must".  On the other hand it clearly warns
that authors and users "must not" rely on specific error recovery
behavior.

ISO/IEC 15445 (a.k.a. ISO-HTML) also clearly states in its introduction [3]
as follows:

  This International Standard does not define error handling procedures.

So I'm not aware of any formal HTML specification(s) that specified
such "must-ignore" policy.  XHTML is an another story.

[1] http://www.w3.org/TR/html4/conform.html#h-4.1
[2] http://www.w3.org/TR/html4/appendix/notes.html#notes-invalid-docs
[3] http://purl.org/NET/ISO+IEC.15445/15445.html#INTRO

Regards,
-- 
Masayasu Ishikawa / mimasa@w3.org
W3C - World Wide Web Consortium
Received on Wednesday, 22 October 2003 03:11:17 GMT

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