RE: DTD and Illegal Construct

["Dudley, Mark" <Mark.Dudley@usa.xerox.com>]

It is an ambiguous content model. You may want to try:

<!ELEMENT Request (A?, B, C?, D?)>

But that might not be what you want.

Mark Dudley
Xerox, Corp.

-----Original Message-----
From: Dan Vint [mailto:dvint@slip.net]
Sent: Wednesday, January 10, 2001 4:14 PM
To: Jim.Shain@alltel.com
Cc: xml-dev@lists.xml.org
Subject: Re: DTD and Illegal Construct


This is an ambiguous content model. The parser (by design in SGML/XML) isn't
supposed to try and figure out which of the two models are being built
if you have element A or B or C in this case, all three will cause the same 
problem.

..dan

> 
> I wanted to run this past some knowledgeable people.  Is the following a
legal
> or illegal construct for an element in a DTD?
> 
>  <!ELEMENT Request ((A, B, C?) | (A?, B, C?, D))>
> 
> Some have stated that it is illegal because "When A is present it isn't
possible
> to determine whether or not D is required."
> 
> Jim Shain
> Sr. C/S Architect
> ALLTEL Information Services
>