DTD Question - PCDATA followed by an optional element

[Thomas B. Passin]

Here's the correct syntax:

<!DOCTYPE test[
   <!ELEMENT comment (#PCDATA)>
   <!ELEMENT rho0 (#PCDATA| comment)*>
]>

It allows any number of comment elements inside a rho0 element, but it seems to
be the only winning combination.
I just tested this with rxp.

Tom Passin


-----Original Message-----
From: Norman H. Samuelson <nhs at llnl.gov>
To: xml-dev at ic.ac.uk <xml-dev at ic.ac.uk>
Date: Wednesday, November 17, 1999 12:04 PM
Subject: DTD Question - PCDATA followed by an optional element


>I have a large number of fields that normally hold simple textual data, but
>might also include a comment.  The XML would look like this with no comment:
>
>   <rho0> 1.0 </rho0>
>
>or this, when the comment is present:
>
>   <rho0> 1.0 <comment> blah, blah </comment> </rho0>
>
>I have no problem in the DTD when I leave out the possibility of a comment,
>I simply use something like this:
>
>   <!ELEMENT rho0 (#PCDATA)>
>
>To include the comment, I would like to be able to simply say:
>
>   <!ELEMENT comment (#PCDATA)>
>   <!ELEMENT rho0 (#PCDATA, comment?)>
>
>That doesn't seem to be acceptable.  I also tried:
>
>   <!ELEMENT rho0 ((#PCDATA) | (#PCDATA, comment))>
>
>Is it possible to do what I want?
>
>If not, I could consider putting one more level of tags around the data,
>like this:
>
>   <rho0> <data> 1.0 </data> <comment> blah, blah </comment> </rho0>
>
>But that adds extra bulk, and code, that should not be needed.  Any
>suggestions would be appreciated.
>
>Whatever solution I come up with must work with IBM's XML4J parser.
>
>
>- Norm -
>
>Norman H. Samuelson                  nhs at llnl.gov
>Lawrence Livermore National Lab      925-422-0661
>P.O. Box 808, L-98
>Livermore, CA 94551
>
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