Extensible select and enumeration types

and their elements in schema Process_property_assignment_arm taking into account BASED_ON types


 activity_item - EXTENSIBLE GENERIC_ENTITY SELECT

 characterized_activity_definition - EXTENSIBLE SELECT
          Activity
          Activity_method

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure