I am using the FURPS+ model for my requirements. And i know Functionality category are functional requirements and the rest are non-functional requirements.
But i was wondering, is validation counted as a functional or non-functional requirements? Validation for user input on an interface. I was thinking to list it as non-functional under the Usability Category.
Am i right to say that?
when you say user input validation, it is integral part of a functionality to be completed. let us say requirement says that input field should not contain any numeric data.So now it is functional requirement.You can verify that this is really need to be mentioned in the requirement.if it is requirement and is mentioned in the document, then this is a functional requirement.If this is not real requirement or may be implicitly implemented due to the implementation of some other functionality then need not worry too much.But nowadays we will validate user inputs for better stability of the application so this can be considered as functional requirement.
To just one thing related to non-functional requirement, performance of the application is not a part of functional requirement.It id the behavior of the application.So that way you can really differentiate it.
