FIGURING OUT WHAT USERS EXPECT (TAKEN FROM USER INTERFACE DESIGN FOR PROGRAMMERS, BY JOEL SPOLSKY)

Program Model and User Model User Model Program Model How the program actually behaves How the user expects the program to behave A user interface is well designed when the program model conforms to the user model

Program Model  How the program behaves  It’s the ‘Law’  Encoded in bits and bytes and will be faithfully executed by the CPU  The CPU will not disobey the Program Model

User Model  How the user expects the program to work  Determined by the user’s history and knowledge  Knowledge of the domain  Knowledge of other user interfaces  History and knowledge of working with other software programs

How Do I Know What The User Model Is?  Turns out to be relatively easy  Ask users  Pick five random people  Picking more than five has little reward  Describe the scenarios and situations where the software will be used  Then ask a lot of questions  Don’t make assumptions

How Do I Know What The User Model Is?  Rule Of Thumb – User models are not very complex  If your program model is complex, it will confuse the user and the program model does not match the user model  When people guess how something works, they tend to guess simple things rather than complicated things

Metaphors  Sometimes the User Model is incomplete or wrong  You have to find ways to give the user clues  Most well known metaphor is the desktop, with folders and files that can be dragged to the trash  Another example is a magnifying glass used to tell the user to zoom  Well designed objects make it clear how they work just by looking at them

Affordances  Well designed affordances make it clear how they work just by looking at them  Example: Doors with a big metal plate. You can’t pull it. You can only push it.  Another Example: 3D buttons with shades of gray that change when clicked. Not just a cool design, but the buttons afford pushing

Consistency  When software works like the user expects, the Program Model matches the User Model  When your user tries to do things, they just “work”  This makes users happy  Happy users are a good thing  Consistency causes ease of use