>You'd like a boolean datatype, so long as it isn't the boolean datatype
>defined in XML Schema, yes?
>
>How exactly would you like it to differ?
>  
>
no difference at all, though I am arguing for the use cases that do not
require the formalism of schema e.g. or even datatypes;

I think that having a simple (is-number / is-string) type functions that
purely test values irregardless of datatype would give just enough
flexibility; and if these functions return boolean then we avoid the
problems such as u describe with something like type-of might present.

exslt:type-of($x) = 'decimal'

in any event, we can include it as a MAY HAVE type option and leave it
to implementators to decide to implement or not.

--Jim