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Re: XML (Schema) Question

From: Soren Kuula <dongfang@--------.-->
To: NULL
Date: 8/7/2005 10:35:00 AM

Mike Busch wrote:
> Jason Karns wrote:
> 
>  > I have a question involving the creation of an XML Schema and am 
> looking for guidance or the name of someone who may be a good person to 
> talk to about this.  The problem is how to properly define a few 
> elements in a schema such that nesting is allowed, but for some 
> elements, nesting of themselves is disallowed.  An example from XHTML:

>  >  but <a> cannot be nested within itself. (<a><span><a></a></span></a> 
> is disallowed.)

>  >  Any suggestions or the name of a good instructor to talk to would be 
> most helpful.

XML Schema can't express that; it's too weak language class.

You can say in XML Schema that the a element is allowed as a child of 
{some elements}. You can also say that a is allowed as a child of b when 
b is a child of c .. and so on, but only to finite height. There's no 
way to express that a is never an ancestor of a.

The Relax NG and DSD2 schema languages can do it..

Søren

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Re: XML (Schema) Question