how to use w3c function exists()

Hallo there,
i tried to use the w3c exists() function to check out whether a node exists in a doc or not.

declare namespace fn = ""
fn:exists(for $q in input()/user
	where $q/key/account='root' and $q/key/password='root'
return $q)

I became this error message: INOXQE6358: Function unknown

Do I have the wrong namespace or
Is this function not supported in Tamino?

Thank u in advance,



please see
for a list of supported functions.

You can usew fn:boolean instead (make sure you use teh correct namespace. fn is predefined, so best is to leave out teh namespace declaration at all)