When given, these items are removed from the items to validate. Excluded items are never included, even when specified via include.
When given, these items are added to the items to validate.
No effect when true or missing.
When false, the validated items are considered to be invalid. All elements are still validated to ensure the
proper error messages are displayed, but the result of the validation will be false (=invalid).
Result value that can be returned by the
begincallback of the form validator, see XmValidator.on and XmValidatorCallbacks.