code: package it.unibz.inf.ontop.model.term.functionsymbol.impl;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.iq.node.VariableNullability;
  import it.unibz.inf.ontop.model.term.Constant;
  import it.unibz.inf.ontop.model.term.ImmutableTerm;
  import it.unibz.inf.ontop.model.term.TermFactory;
  import it.unibz.inf.ontop.model.type.RDFDatatype;
  import it.unibz.inf.ontop.model.type.TermTypeInference;
  
  import javax.annotation.Nonnull;
  import java.util.Optional;
  
  
  public class EBVSPARQLLikeFunctionSymbolImpl extends SPARQLLikeFunctionSymbolImpl {
  
      private final RDFDatatype xsdBooleanType;
  
      protected EBVSPARQLLikeFunctionSymbolImpl(@Nonnull RDFDatatype rootDatatype, RDFDatatype xsdBooleanType) {
          super("SP_EBV", ImmutableList.of(rootDatatype));
          this.xsdBooleanType = xsdBooleanType;
      }
      @Override
      protected boolean tolerateNulls() {
          return false;
      }
  
      @Override
      public boolean isAlwaysInjectiveInTheAbsenceOfNonInjectiveFunctionalTerms() {
          return false;
      }
  
      @Override
      public Optional<TermTypeInference> inferType(ImmutableList<? extends ImmutableTerm> terms) {
          return Optional.of(TermTypeInference.declareTermType(xsdBooleanType));
      }
  
      @Override
      public boolean canBePostProcessed(ImmutableList<? extends ImmutableTerm> arguments) {
          return false;
      }
  
      @Override
      protected final ImmutableTerm buildTermAfterEvaluation(ImmutableList<ImmutableTerm> newTerms,
                                                             TermFactory termFactory, VariableNullability variableNullability) {
          ImmutableTerm newTerm = newTerms.get(0);
  
          if (isRDFFunctionalTerm(newTerm) || (newTerm instanceof Constant)) {
  
              ImmutableTerm subLexicalTerm = extractLexicalTerm(newTerm, termFactory);
              ImmutableTerm subTypeTerm = extractRDFTermTypeTerm(newTerm, termFactory);
  
              ImmutableTerm lexicalTerm = computeLexicalTerm(subLexicalTerm, subTypeTerm, termFactory)
                      .simplify(variableNullability);
  
              // NB: Only there for improving the performance
              if (lexicalTerm.equals(termFactory.getNullConstant()))
                  return lexicalTerm;
  
              ImmutableTerm typeTerm = termFactory.getIfElseNull(
                      termFactory.getDBIsNotNull(lexicalTerm),
                      termFactory.getRDFTermTypeConstant(xsdBooleanType))
                      .simplify(variableNullability);
  
              return termFactory.getRDFFunctionalTerm(lexicalTerm, typeTerm);
          }
          else
              return termFactory.getImmutableFunctionalTerm(this, newTerms);
      }
  
      protected ImmutableTerm computeLexicalTerm(ImmutableTerm subLexicalTerm, ImmutableTerm subTypeTerm, TermFactory termFactory) {
          return termFactory.getConversion2RDFLexical(
                  termFactory.getLexicalEffectiveBooleanValue(subLexicalTerm, subTypeTerm),
                  xsdBooleanType);
      }
  }
  