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Re: [VE][141] Validator throws "not-unique" error on Case Sensitive IDs

From: John Lascurettes <John.Lascurettes@providence.org>
Date: Fri, 26 Jan 2007 14:59:53 -0800
To: <www-validator@w3.org>
Message-ID: <C1DFC7E9.3DFF%John.Lascurettes@providence.org>

I see. Thank you. I also tested this out as XHTML which throws no errors.
This is consistent with the differences between XML and SGML I am assuming.

I had already made a change in my document to make the the IDs unique in a
case insensitive context. But I always like to know the details.

On 2007|01|26 14:42, "Jukka K. Korpela" <jkorpela@cs.tut.fi> wrote:

> On Fri, 26 Jan 2007, John Lascurettes wrote:
>> This paragraph has attribute id="Unique"
>> This paragraph has attribute id="uNIQUE"
>> The Validator throws this error:
>> ID "UNIQUE" already defined.
> The validator is correct. The HTML specification is misleading.
>> Shouldn't they be considered not the same ID since the ID attribute is
>> defined as case sensitive
> It's labeled "CS" (for Case Sensitive), but that's really just an
> annotation, especially when we consider that formally HTML 4.01
> specification defines the language as an SGML application and declares the
> id attribute as being of type ID. By SGML rules, ID values are internally
> converted to upper case. (You need to read the SGML standard carefully to
> find this, but there's a hint: it's mentioned in the tutorial annex in the
> "SGML Handbook" on p. 52.)
> This explains the spelling "UNIQUE" in the error message, too.
> The prose in the HTML 4.01 specification gives a wrong impression. It's
> also more or less self-contradictory, since at
> http://www.w3.org/TR/html4/struct/links.html#h-12.2.1
> it says:
> "An anchor name is the value of either the name or id attribute when used
> in the context of anchors. Anchor names must observe the following rules:
> - Uniqueness: Anchor names must be unique within a document. Anchor names
> that differ only in case may not appear in the same document.
> - String matching: Comparisons between fragment identifiers and anchor
> names must be done by exact (case-sensitive) match."
> Since the names are converted to upper case by SGML rules, the case issue
> cannot arise. We can think that the second item wants to say that a
> reference like href="#foo" should refer to an anchor with the literal
> spelling "foo" (and not "FOO" which is its _meaning_).
> This is of little practical value since browsers never really implemented
> HTML as an SGML application in issues like this. They use some matching
> routines souped up by someone who didn't really bother reading the SGML
> standard (either). But the bottom line is that browsers could do
> this either way, so just don't use id values or other anchor names that
> differ in case only.

John Lascurettes
Specialist - Interactive Web Design
Providence Health System
Marketing & Communications

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Received on Friday, 26 January 2007 23:05:22 UTC

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