code: private void setRDFAsDatastream(StringBuffer buf) {
  
          DatastreamXMLMetadata ds = new DatastreamXMLMetadata();
          // set the attrs common to all datastream versions
          ds.DatastreamID = "RELS-INT";
          ds.DSVersionable = false;
          ds.DSFormatURI = m_dsFormatURI;
          ds.DatastreamAltIDs = m_dsAltIDs;
          ds.DSVersionID = "RELS-INT.0";
          ds.DSLabel =
                  "DO NOT EDIT: System-generated datastream to preserve METS DMDID/ADMID relationships.";
          ds.DSCreateDT = new Date();
          ds.DSMIME = "application/rdf+xml";
          // set the attrs specific to datastream version
          ds.DSControlGrp = "X";
          ds.DSState = "A";
          ds.DSLocation =
                  m_obj.getPid() + "+" + ds.DatastreamID + "+" + ds.DSVersionID;
          ds.DSLocationType = Datastream.DS_LOCATION_TYPE_INTERNAL;
          ds.DSInfoType = "DATA";
          ds.DSMDClass = DatastreamXMLMetadata.TECHNICAL;
  
          // now set the xml content stream itself...
          try {
              ds.xmlContent = buf.toString().getBytes(m_characterEncoding);
              ds.DSSize = ds.xmlContent.length;
          } catch (UnsupportedEncodingException uee) {
              logger.error("Encoding error when creating RELS-INT datastream", uee);
          }
          // FINALLY! add the RDF and an inline xml datastream in the digital object
          m_obj.addDatastreamVersion(ds, true);
      }
docs: DMDID and ADMID relationships found in the METS file.