[...]...A user interface is well designed when the program model conforms to the user model That's it Almost all good user interface design comes down to bringing the program model and the user model in line The Macintosh UI would have been more successful (especially for my poor friend) if it saved your "unsaved" work for you Of course, in 1985, the slow speed of... since users are completely free to ignore the choice and get their work done anyway, this is a good use of options 20 Chapter 4: Affordances and Metaphors Overview Developing a user interface where the program model matches the user model is not easy Sometimes, your users might not have a concrete expectation of how the program works and what it's supposed to do There is no user model When the user. .. lot of things, and it is the designers' responsibility to make these choices for them so that they don't have to It is the height of arrogance for a software designer to inflict a choice like this on the user simply because the designer couldn't think hard enough to decide which option is really better (It's even worse when you try to cover up the fact that you're giving the user a difficult choice by... GUIs yet and is expecting a command-line interface How many users do you need to test your interface on? The scientific approach seems like it would be "the more, the better." If testing on five users is good, testing on twenty users is better! But that approach is flat-out wrong Almost everybody who does usability testing for a living agrees that five or six users is all you need After that, you start... your time," to paraphrase) And it's pretty obvious that the designers had some idea as to which choice is best; after all, they've gone to the trouble of recommending one of the choices Which brings us to our second major rule of user interface design: Every time you provide an option, you're asking the user to make a decision Asking the user to make a decision isn't in itself a bad thing Freedom of... cellophane, one for each application The windows are ‘glued’ to those invisible sheets When you bring Excel to the foreground, you are really clicking on the cellophane, so all the other windows from Excel should move forward too without changing their order." Riiiiiiiiight Invisible sheets What are the chances that the user model included the concept of invisible sheets? Probably zero The user model is... beneath the document file—this, at least, conforms to the user' s idea that the picture is copied (and the original can safely be deleted) How Do I Know What the User Model Is? This turns out to be relatively easy Just ask some users! Pick five random people in your office, or friends, or family, and tell them what your program does in general terms ("it's a program for making Web pages") Then describe the... But it's a safe bet that more Kai users will be able to zoom in than Word users Affordances 22 Well-designed objects make it clear how they work just by looking at them Some doors have big metal plates at arm-level The only thing you can do to a metal plate is push it You can't pull it You can't rotate it In the words of usability expert Donald Norman, the plate affords pushing Other doors have big,... metaphor at all Unfortunately, desktop user interface designers feel that they're breaking some kind of law if they don't use metaphors, so they would rather pick a wrong metaphor than go without When you use metaphors, try to make them behave in predictable ways like objects in the real world.Violating reality is just confusing What's the purpose of a metaphor in the first place? To teach users what the... embedded—but this has two problems: it's annoying to sophisticated users; and users don't read dialog boxes, either We'll talk more about this in Chapter 9 So, if the mountain won't come to Muhammad, Muhammad must go to the mountain Your best choice is almost always going to be to change the program model, not the user model Perhaps when the user inserts picture, the program should make a copy of the picture . we're designing for users, but no matter how hard we try, we're designing for who we think the user is, and that means, sadly, that we're designing. The interface needs to behave in the way they expect it to behave. Thus, the cardinal axiom of all user interface design: A user interface is well designed