Used by abstract functions to define how new functions are created by
the factory. Note that all functions using XPath are defined to be
abstract functions, so they must be created using this interface.
Creates an instance of some abstract function. If the function
being created is not using XPath, then the version parameter can be
ignored, otherwise a value must be present and the version must
be acceptable.
Parameters:
root - the DOM root of the apply statement containing the function
xpathVersion - the version specified in the contianing policy, or
null if no version was specified
Returns:
the function
Throws:
Exception - if the underlying code experienced any error