code: package it.unibz.inf.ontop.model.term.functionsymbol.db.impl;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.model.term.ImmutableTerm;
  import it.unibz.inf.ontop.model.term.functionsymbol.db.DBFunctionSymbol;
  import it.unibz.inf.ontop.model.term.functionsymbol.impl.FunctionSymbolImpl;
  import it.unibz.inf.ontop.model.type.DBTermType;
  import it.unibz.inf.ontop.model.type.TermType;
  import it.unibz.inf.ontop.model.type.TermTypeInference;
  
  import java.util.Optional;
  
  public abstract class AbstractTypedDBFunctionSymbol extends FunctionSymbolImpl implements DBFunctionSymbol {
  
      private final DBTermType targetType;
  
      protected AbstractTypedDBFunctionSymbol(String name, ImmutableList<TermType> expectedBaseTypes, DBTermType targetType) {
          super(name, expectedBaseTypes);
          this.targetType = targetType;
      }
  
      public DBTermType getTargetType() {
          return targetType;
      }
  
      @Override
      public Optional<TermTypeInference> inferType(ImmutableList<? extends ImmutableTerm> terms) {
          return Optional.of(TermTypeInference.declareTermType(targetType));
      }
  
      @Override
      protected boolean mayReturnNullWithoutNullArguments() {
          return false;
      }
  
      @Override
      protected boolean tolerateNulls() {
          return false;
      }
  
      /**
       * By default, to be overridden when necessary
       */
      @Override
      public boolean isPreferringToBePostProcessedOverBeingBlocked() {
          return false;
      }
  }
  