@abc.abstractmethod<EOL><INDENT>def get_default_duration_values(self):<DEDENT>
return<EOL>
Gets the default duration values.

        These are the values used if the element value is not provided
        or is cleared. If ``is_array()`` is false, then this method
        returns at most at most a single value.

        :return: the default duration values
        :rtype: ``osid.calendaring.Duration``
        :raise: ``IllegalState`` -- syntax is not a DURATION or ``is_required()`` is ``true``

        *compliance: mandatory -- This method must be implemented.*