private Item instantiateFuzzyItem(String field, OperatorNode<ExpressionOperator> ast) {
        List<OperatorNode<ExpressionOperator>> args = ast.getArgument(1);
        Preconditions.checkArgument(args.size() == 1, "Expected 1 argument, got %s.", args.size());

        String wordData = getStringContents(args.get(0));

        Integer maxEditDistance = getAnnotation(
                ast,
                MAX_EDIT_DISTANCE,
                Integer.class,
                FuzzyItem.DEFAULT_MAX_EDIT_DISTANCE,
                MAX_EDIT_DISTANCE_DESCRIPTION);

        Integer prefixLength = getAnnotation(
                ast,
                PREFIX_LENGTH,
                Integer.class,
                FuzzyItem.DEFAULT_PREFIX_LENGTH,
                PREFIX_LENGTH_DESCRIPTION);

        boolean prefixMatch = getAnnotation(
                ast,
                PREFIX,
                Boolean.class,
                Boolean.FALSE,
                "setting for whether to use prefix match of input data");

        FuzzyItem fuzzy = new FuzzyItem(field, true, wordData, maxEditDistance, prefixLength, prefixMatch);
        return leafStyleSettings(ast, fuzzy);
    }
Build a "pure" not, without any positive terms.
container-search/src/main/java/com/yahoo/search/yql/YqlParser.java