Extensible select and enumeration types

and their elements in schema DOCUMENT_ASSIGNMENT_XIM taking into account BASED_ON types


 document_reference_item - EXTENSIBLE SELECT

 external_identification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          document_definition
          document_file
          file
          product_definition

 identification_item - EXTENSIBLE SELECT
          document_file

 versionable_item - EXTENSIBLE SELECT
          document_file