code: package it.unibz.inf.ontop.model.term.functionsymbol.impl;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.model.term.ImmutableExpression;
  import it.unibz.inf.ontop.model.term.ImmutableTerm;
  import it.unibz.inf.ontop.model.term.TermFactory;
  import it.unibz.inf.ontop.model.type.DBTypeFactory;
  import it.unibz.inf.ontop.model.type.RDFDatatype;
  import it.unibz.inf.ontop.model.vocabulary.XPathFunction;
  
  public class NotSPARQLFunctionSymbolImpl extends AbstractUnaryBooleanSPARQLFunctionSymbol {
  
      private final RDFDatatype xsdBooleanType;
  
      protected NotSPARQLFunctionSymbolImpl(RDFDatatype xsdBooleanType) {
          super("SP_NOT", XPathFunction.NOT, xsdBooleanType, xsdBooleanType);
          this.xsdBooleanType = xsdBooleanType;
      }
  
      @Override
      protected ImmutableExpression computeExpression(ImmutableList<ImmutableTerm> subLexicalTerms, TermFactory termFactory) {
          DBTypeFactory dbTypeFactory = termFactory.getTypeFactory().getDBTypeFactory();
  
          return termFactory.getDBNot(
                  (ImmutableExpression) termFactory.getConversionFromRDFLexical2DB(
                          dbTypeFactory.getDBBooleanType(),
                          subLexicalTerms.get(0),
                          xsdBooleanType));
      }
  
      @Override
      public boolean isAlwaysInjectiveInTheAbsenceOfNonInjectiveFunctionalTerms() {
          return true;
      }
  }
  