User input validation

A very well understood concept in computer programming is that of 'validation'. In its basic form it's just a predicate which determines whether data conforms to some predetermined rules. Combined with a principle that problems should be identified as early as possible, this leads to the most common application: having a method call, we first validate input arguments before proceeding with any business logic (checking preconditions). If validation doesn't pass, we return some hints as to what went wrong. Sometimes the information we provide event suffices to painlessly fix the issue.

Now, validation is also very widespread in HCI, where computer validates user input. As with all thing human however, this gets a little bit more tricky. You see, as a user, I'm not interested in bureaucracy in the slightest. It annoys me when I'm told "your application form is invalid". I expect software to guide me as I try to express my intentions. And while validation errors are a form of guidance, they tend to occur too late and tend to suggest user failure. You'd usually want someone who is willing to provide as much help as possible instead of accepting/rejecting your application and referencing some article no. in "rules".

Anyway, looks like this exploration-based model will dominate the transaction-based model in HCI. And the  simple "form validation" is falling apart here. At least, it should be way more granular, and ideally there should be no "validation errors". You just want your computer usage to be a pleasant experience, without any error popups. It seems often to be much better to just ignore incorrect input, rather than scream loudly "I don't understand what you mean, fool". Quite the opposite to what we do with validation in our code for API.