Questions?• Project #2• HW#4 inThe EconomistInterface metaphors• Definition– Use of one kind of object or idea in place of another to suggest a likeness or analogy between them• Purposed– Leverages our knowledge of familiar, concrete objects/experiences– Transfer this knowledge to abstract computer and task concepts• Examples– Desktop, files, folders, trash can…– Paintbrush in a painting programMetaphors caveats• Too limited– The metaphor restricts interface possibility• Too powerful– The metaphor makes believe that the system can do things it can’t• Too literal or cute– Make it difficult to operate• Mismatched– The metaphor makes it difficult to carry out the taskDirect manipulation: Good or Evil?• Good for intermediate users– Recognition versus recall trade-off• Explicit versus implicit command– “rename each file by adding ‘_old’ to its name”• Limit of reification– How to align an object?• Metaphor might be too restrictive– WYSIAYG: What You See Is All You Get • Applications mix– Direct manipulation• Tools, drag and drop interactions…– Abstraction • Menus, dialog boxes,…Usability heuristics• “Rules of thumb” that describe features of usable systems– Can be used as design principles– Can be used to evaluate a design• Pros and cons– Easy and inexpensive• Performed by expert• No users required• Catch many design flaws– More difficult than it seems• Not a simple checklist• Cannot assess how well the interface will address user goalsUsability Engineering• Introduced by Nielsen (1994)• Can be performed on working UI or sketches• Required a small set (3-5) of evaluators to examine the UI– Check compliance with usability principles• Each evaluator works independently• Go through the interface several times– All reviews are aggregated in one final usability reportNielsen's evaluation phases (1-2)• Pre-evaluation training– Provide the evaluator with domain knowledge if needed• Evaluation– First step: get a feel for flow and scope– Second step: focus on specific elements• Multiple passes approach is better• Create a list of all problemsNielsen's evaluation phases (3-4)• Severity rating– Performed after individual evaluations are aggregated– Establishes a ranking between problem– Reflects frequency, impact and persistence• Cosmetic, minor, major and catastrophic• Debriefing– Discuss outcome with design team– Suggest potential solutions– Assess how hard things are to fixNeilsen’s heuristics• Simple and natural dialog• Speak the users’ language• Minimize user memory load• Consistency• Feedback• Clearly marked exits• Shortcuts• Prevent errors• Good error messages• Provide help and documentationSimple and natural dialogFrom Cooper’s “The inmates are running the asylum”Simple and natural dialog• Present information in natural order• Occam’s razor– Remove or hide irrelevant or rarely needed information• They compete with important information on screen– Pro: Palm Pilot– Against: Dynamic menus– Use windows frugally• Avoid complex window managementFrom Cooper’s “About face 2.0”Speak the users’ language• Use a language compatible with users’ conceptual model– Example: withdrawing money at an ATM• Use meaningful mnemonics, icons and
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