DDIF_Input_Converter

   The DDIF input converter converts a compound document DDIF input
   file to an intermediate format that is then converted to the
   specified output file format. If the DDIF input file is a newer
   version of the DDIF grammar than that understood by the DDIF
   input converter, data represented by the new grammar elements is
   lost.

   The DDIF input converter does not resolve external references,
   although the converter kernel can if requested by the output
   converter. A document syntax error in the DDIF input file causes
   a fatal input processing error and conversion stops.