@Override
            public boolean isValid() {
                try {
                    checkValid();
                    return true;
                } catch (DatatypeException e) {
                    return false;
                }
            }
@see nu.validator.datatype.AbstractDatatype#createStreamingValidator(org.relaxng.datatype.ValidationContext)
src/nu/validator/datatype/AbstractUnicodeClassCharacter.java