Spring 2008 6.831 User Interface Design and Implementation 1Lecture 12: User Control & Freedom UI Hall of Fame or Shame?Spring 2008 6.831 User Interface Design and Implementation 2 This is the Windows XP Search Companion. It appears when you press the Search button on a Windows Explorer toolbar, and is primarily intended for finding files on your hard disk. An interesting feature of this interface is that, rather than giving a textbox for search keywords right away, it first asks you to specify what kind of file you’re looking for. Let’s think about: - learnability (what overall design pattern is being used here?) - user control & freedom - efficiency - error prevention – can you anticipate an error in the second picture? (Hint: find two buttons with identical labels)UI Hall of Fame or Shame?Spring 2008 6.831 User Interface Design and Implementation 3Suggested by Mariela Buchin Now here’s the Start menu in Vista, which is similar to the Start menu in Windows XP and other desktops, but it adds an interesting new feature: a search box that incrementally searches through programs, web favorites, files, and emails. Think about: - efficiency - consistency - visibility Quicksilver for Mac OS offers a similar feature (although Quicksilver is much different in the details; we may look at it in a future Hall of Fame or Shame). Today’s Topics• User control over the dialog• User control over data•UndoSpring 2008 6.831 User Interface Design and Implementation 4 Today’s lecture is about user control and freedom (a term coined by Jakob Nielsen), which is the idea that in the give and take between the user and the system, the user should have ultimate control. We’ve touched on this idea several times in previous lectures. It’s one of the reasons we use event-driven programming in graphical user interfaces, for example, rather than synchronous prompt-and-response. But user control has design implications beyond that low-level detail. We’ll focus on two kinds of control in this lecture: control over the dialog (who says what when), and control over the data (e.g., what the user can enter, and whether it can be changed later). A common design pattern for increasing user control is undo. We’ll look at undo in detail, and see that it’s more complicated than it appears.Why the User Should Be In Control• Learning by exploring• Dealing with errors• User is sentient, computer is notSpring 2008 6.831 User Interface Design and Implementation 5 Good interfaces are explorable. One way users learn is by exploring: poking around an interface, trying things out. An interface should encourage this kind of exploration, not only by making things more visible, but also by making the consequences of errors less severe. For example, users navigating around a 3D world or a complex web site can easily get lost; give them an easy, obvious way to get back to some “home”, or default view. Users should be able to explore the interface without fear of being trapped in a corner. Clearly Marked Exits• Long operations should be cancelable• All dialogs should have a cancel buttonSpring 2008 6.831 User Interface Design and Implementation 6Source: Interface Hall of Shame The simplest kind of user control is a veto – the ability to cancel an operation, even if it was something they asked for. Users should not be trapped by the interface. Long operations should not only have a progress bar, but a Cancel button too. Likewise, every dialog box should have a Cancel button. Where is it in this CuteFTP dialog box on the bottom? As a user of this dialog, would you feel like you’re in control? Wizard vs. Center Stage: Who’s in Control?Spring 2008 6.831 User Interface Design and Implementation 7WizardCenter Stage Let’s look a little further at who controls the dialog between the user and the system. (Here, dialog means the general pattern of back-and-forth communication between the user and the interface, as if the user and the system are having a conversation. A dialog box is a specific kind of window, a design pattern used in a dialog. We often say dialog as a shorthand for dialog box, but hopefully the distinction will be obvious from context.) We’ll contrast two patterns. The wizard design pattern is a familiar pattern for improving the learnability of a complex interaction, by structuring it as a step-by-step process, with each step in a dialog. Wizards are the conventional pattern forsoftware installation. In a wizard, the system controls the dialog – it dictates the steps, the ordering of the steps, and what it asks for at each step. Imagine a travel agent who’s asking you a series of questions, and refuses to listen to what you say if it’s not relevant to the question they asked. That’s a wizard. Contrast that with the center stage pattern, which lays out data objects in the main section of the window, and gives the user a set of tools for operating on the objects. In this case, the user controls the dialog, deciding which objects to select and which tools to pick up. Wizards clearly restrict the user’s freedom, but for complex, infrequently-done tasks (like installation), the tradeoff is often worth it. Note, however, that a good wizard has two key features: a Back button (for backing out of errors) and a Cancel button (for vetoing the operation entirely). So even though the wizard pattern puts the system in control of the details, the user still has supervisory control. Manual Overrides for Automatic SystemsSpring 2008 6.831 User Interface Design and Implementation 8Source: www.findability.org One of the main reasons we build software in the first place is to automate a process, taking some burden off the human users. But we can’t take away control entirely. Users should be able to manually override automation. The familiar Find & Replace command is a simple example of this. If Find & Replace were perfectly automatable, then all we’d need is Replace All. But the world isn’t that simple, and our documents are full of exceptions or incompletely-specified patterns, and there are plenty of cases where the user needs manual control over replacement – hence the Replace button. Google Maps offers an example of a different kind of control – starting with the output of an automatic algorithm (the shortest route between two points) and manually tweaking it (dragging the route around). Systems that solve big or complex
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