code: package it.unibz.inf.ontop.model.term.functionsymbol.db.impl;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableSet;
  import it.unibz.inf.ontop.iq.node.VariableNullability;
  import it.unibz.inf.ontop.model.term.*;
  import it.unibz.inf.ontop.model.term.functionsymbol.db.DBFunctionSymbolSerializer;
  import it.unibz.inf.ontop.model.type.DBTermType;
  import org.eclipse.rdf4j.model.datatypes.XMLDatatypeUtil;
  
  import java.util.Optional;
  import java.util.function.Function;
  
  public abstract class AbstractTimestampISONormFunctionSymbol extends AbstractDBTypeConversionFunctionSymbolImpl {
  
      protected final DBTermType timestampType;
      private final DBFunctionSymbolSerializer serializer;
  
      protected AbstractTimestampISONormFunctionSymbol(DBTermType timestampType, DBTermType dbStringType,
                                                       DBFunctionSymbolSerializer serializer) {
          super("iso" + timestampType.getName(), timestampType, dbStringType);
          this.timestampType = timestampType;
          this.serializer = serializer;
      }
  
      @Override
      public Optional<DBTermType> getInputType() {
          return Optional.of(timestampType);
      }
  
      @Override
      public boolean isTemporary() {
          return false;
      }
  
      @Override
      public boolean isSimple() {
          return false;
      }
  
      @Override
      public boolean isAlwaysInjectiveInTheAbsenceOfNonInjectiveFunctionalTerms() {
          return true;
      }
  
      @Override
      public boolean canBePostProcessed(ImmutableList<? extends ImmutableTerm> arguments) {
          return false;
      }
  
      @Override
      public String getNativeDBString(ImmutableList<? extends ImmutableTerm> terms,
                                      Function<ImmutableTerm, String> termConverter, TermFactory termFactory) {
          return serializer.getNativeDBString(terms, termConverter, termFactory);
      }
  
      @Override
      protected IncrementalEvaluation evaluateStrictEqWithNonNullConstant(ImmutableList<? extends ImmutableTerm> terms,
                                                                          NonNullConstant otherTerm, TermFactory termFactory,
                                                                          VariableNullability variableNullability) {
          if (!XMLDatatypeUtil.isValidDateTime(otherTerm.getValue()))
              return termFactory.getBooleanIfElseNull(termFactory.getDBIsNotNull(terms.get(0)),
                      termFactory.getIsTrue(termFactory.getDBBooleanConstant(false)))
                      .evaluate(variableNullability, true);
  
          return evaluateStringEqWithValidDatetimeConstantString(terms.get(0), otherTerm, termFactory, variableNullability);
      }
  
      protected IncrementalEvaluation evaluateStringEqWithValidDatetimeConstantString(ImmutableTerm subTerm,
                                                                                    NonNullConstant otherTerm,
                                                                                    TermFactory termFactory,
                                                                                    VariableNullability variableNullability) {
          return IncrementalEvaluation.declareSameExpression();
      }
  }
  