The name of the parameter, expressed
as a QName. If a parameter of this name has been declared in the
stylesheet, the given value will be assigned to the variable. If the
variable has not been declared, calling this method has no effect (it is
not an error).
value
The value to be given to the parameter.
If the parameter declaration defines a required type for the variable, then
this value will be converted in the same way as arguments to function calls
(for example, numeric promotion is applied).