code: private SQLPPTriplesMap getMapping(TriplesMap tm) throws Exception {
  		String sourceQuery = r2rmlParser.getSQLQuery(tm).trim();
  		ImmutableList<TargetAtom> body = getMappingTripleAtoms(tm);
  		//Function head = getHeadAtom(body);
  		//CQIE targetQuery = DATALOG_FACTORY.getCQIE(head, body);
  		// TODO: consider a R2RML-specific type of triples map
  		SQLPPTriplesMap mapping = new OntopNativeSQLPPTriplesMap("mapping-"+tm.hashCode(),
  				MAPPING_FACTORY.getSQLQuery(sourceQuery), body);
          if (body.isEmpty()){
              //we do not have a target query
              System.out.println("WARNING a mapping without target query will not be introduced : "+ mapping.toString());
              return null;
          }
  		return mapping;
  	}
docs: Get OBDA mapping axiom from R2RML TriplesMap
  @param tm
  @return
  @throws Exception