What is an "illegal binding expression"?

As part of our discussion of  
http://lists.w3.org/Archives/Public/www-forms/2010Jun/0005.html
which refers to section http://www.w3.org/TR/xforms11/#evt-bindingException

There we say "The xforms-binding-exception Event
Dispatched as an indication of: an illegal binding expression, or ..."

without defining what an illegal binding expression is.

So, I would like to ask all implementors this: under what circumstances do  
you generate this event. Then maybe we can come to a consensus on a  
definition.

Thanks.

Best wishes,

Steven

Received on Wednesday, 8 September 2010 16:06:46 UTC