Via Ian Cartwright an interview with “Lean software gurus” Mary and Tom Poppendieck. All is going well until Mary says this:
When do you really need to design a user interface? Oftentimes it drives the whole design, but in fact you don’t really need it until you’re about to do your first alpha test. Before that you can be designing the business layer and you can actually put testing in below the user interface and you can be designing all of the other business logic; you can get that done with any kind of interface and in fact you ca drive testing with a automated interface, and then just before you go to alpha testing you decide what you want for your user interface. Then you take it off and at that point in time you figure it out. But up until that point in time you don’t need that.
This jars with my experience of building compelling customer experiences. There is a good reason why the user interface should drive the whole design because that is how the software is manifest. To the people whose lives are to be touched by the software, the users, the consumers, the interface is the software. To leave the UI till last presents a huge risk of building software that is functionally rich but has a UI modelled around the features; the underlying data and logic rather than how the user wants to work.
Starting with the UI is an excellent way of capturing and communicating requirements. And bakes in usability into the design. You want this feature and that feature? Great. But will they be coherent and usable to the user? Drawing out a UI on paper – paper prototyping- is far more efficient that making assumptions about requirements on a list. Afterall, isn’t this what the manufacturing industry that the Poppendiecks take thier inspiration from? Don’t the car manufacturers start with CAD and move onto clay models? Ergonomists have a hand in the design of car interiors, using anthropometrics to build in comfort and work out lines of sight. The engineers don’t build the engine and the bodywork and then make decisions about how the car will look. These things are designed from the start. And so should it be with software.
When do you really need to design a user interface? It should be the first thing that you do.