code: package it.unibz.inf.ontop.model.term.functionsymbol.db.impl;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.model.term.Constant;
  import it.unibz.inf.ontop.model.term.TermFactory;
  import it.unibz.inf.ontop.model.term.functionsymbol.db.DBFunctionSymbolSerializer;
  import it.unibz.inf.ontop.model.type.DBTermType;
  
  import javax.annotation.Nonnull;
  
  public class NullIgnoringDBGroupConcatFunctionSymbol extends AbstractDBAggregationFunctionSymbol {
  
      protected NullIgnoringDBGroupConcatFunctionSymbol(@Nonnull DBTermType dbStringType, boolean isDistinct,
                                                        @Nonnull DBFunctionSymbolSerializer serializer) {
          super("DB_GROUP_CONCAT", ImmutableList.of(dbStringType, dbStringType), dbStringType, isDistinct, serializer);
      }
  
      @Override
      public Constant evaluateEmptyBag(TermFactory termFactory) {
          return termFactory.getDBStringConstant("");
      }
  
      @Override
      protected boolean isAlwaysInjectiveInTheAbsenceOfNonInjectiveFunctionalTerms() {
          return false;
      }
  
      @Override
      protected boolean tolerateNulls() {
          return true;
      }
  
      @Override
      protected boolean mayReturnNullWithoutNullArguments() {
          return false;
      }
  }
  