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- From: "Stewart Rubenstein" <sdr@camsoft.com>
- To: "'XML-Dev Mailing list'" <xml-dev@ic.ac.uk>
- Date: Mon, 13 Sep 1999 17:40:58 -0400
It's important to distinguish between empty-value and not-present.
Empty-value for enumerated types is simply not supported. You have to use a
value like "none" or "unspecified" and use an extra layer of filtering if
your application requires the empty string for these cases internally. I'd
like to be able to say
<!ATTLIST foo ( a | b | c | ) "a"> <!-- default is "a", but "" is also
permitted -->
<!ATTLIST bar ( a | b | c | ) ""> <!-- default is empty, not
not-present -->
but AFAIK I can't express this in a DTD. I don't think it's what you were
asking.
However, not-present *is* supported as the default value, that's exactly
what #IMPLIED gets you. Not-present is not supported as a non-default
value.
I don't know whether Tim was talking about empty-value support or
not-present as a non-default value. I would find empty-value support
helpful in making my documents and processing more natural, but I can work
around that problem. I don't see a need for not-present as a non-default
value, myself.
-Stew
CTO, CambridgeSoft Corp
> -----Original Message-----
> My original question:
> http://www.lists.ic.ac.uk/hypermail/xml-dev/xml-dev-Sep-1999/0606.html
> (basically, is it legit to use #IMPLIED on the declaration for an
> enumerated attribute type and NOT specify a value in the document.)
>
> At 05:22 PM 9/10/99 -0400, John Cowan wrote:
> http://www.lists.ic.ac.uk/hypermail/xml-dev/xml-dev-Sep-1999/0636.html
> (basically, yes. XHTML does it.)
>
> At 02:32 PM 9/10/99 -0700, Tim Bray wrote:
> http://www.lists.ic.ac.uk/hypermail/xml-dev/xml-dev-Sep-1999/0609.html
> (basically, no, but it would be nice to see in schemas.)
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