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Re: 4. ID assignment and the empty string

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Fri, 28 Jan 2005 09:21:24 +0000
To: Ian Hickson <ian@hixie.ch>
Cc: Norman Walsh <Norman.Walsh@Sun.COM>, public-xml-id@w3.org
Message-ID: <f5bis5hgb8r.fsf@erasmus.inf.ed.ac.uk>

Seems to me we're confusing two things here, which the XML REC (and
xml:id as proposed) are careful to keep separate

 1) An attribute having type ID;
 2) A string being the ID of an element.

(1) is necessary but not sufficient for (2).  For (2) to hold
additional things must be true:

  2a) The string must be a valid NCName;
  2b) There must not be another attribute of type ID with the same
      string value;
  . . .

I don't see why it's necessary for xml:id to say anything more than it
has -- as Norm pointed out, 

<!DOCTYPE doc [
<!ATTLIST doc id ID #IMPLIED>
]>
<doc id=""/>

and

<doc xml:id=""/>

both have attributes of type ID, and neither has an IDentified
element.

UAs already do the right thing with the first case, I believe -- why
shouldn't they do the right thing with the second, without xml:id
having to say anything more than it does already?

ht
-- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Friday, 28 January 2005 09:21:32 UTC

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