If that's the case, the library should also have another function or method that can validate the barcode if the application should so choose. The library is th

If that's the case, the library should also have another function or method that can validate the barcode if the application should so choose. The library is the barcode expert, the app is the business logic expert. Expecting every app to now become barcode experts doesn't make sense. Also, that law gets quoted, and IMO is a rather large design mistake.