code: private void readAssignmentExtendedAttributes(Project.Assignments.Assignment xml, ResourceAssignment mpx)
     {
        for (Project.Assignments.Assignment.ExtendedAttribute attrib : xml.getExtendedAttribute())
        {
           int xmlFieldID = Integer.parseInt(attrib.getFieldID()) & 0x0000FFFF;
           AssignmentField mpxFieldID = MPPAssignmentField.getInstance(xmlFieldID);
           TimeUnit durationFormat = DatatypeConverter.parseDurationTimeUnits(attrib.getDurationFormat(), null);
           DatatypeConverter.parseExtendedAttribute(m_projectFile, mpx, attrib.getValue(), mpxFieldID, durationFormat);
        }
     }
docs: This method processes any extended attributes associated with a
  resource assignment.
  
  @param xml MSPDI resource assignment instance
  @param mpx MPX task instance