> do you mean that, which I took to mean check for
>    <xxx id="1" id="2"/>

No David, even I knew that to be wrong.



> 
> which can't happen in an XSL input tree, or do you mean checking the
> normal ID constraint that no two ids in the same document 
> have the same
> value
Yes, thats it.


 which is
> test="count(//*[@id='x'])=1"
> or
> test="not((//*[@id='x'])[2])"

Yes, thats it. I seem to remember a somewhat esoteric method of checking
this,
but that one does work. The negated option makes error reporting easier.

Thanks, DaveP

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