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Design and Interaction, Part 2 31 January 2006 Kathy E. Gill
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Our goal : flow The process of an optimal experience The activity feels seamless It is intrinsically enjoyable Individual loses self-consciousness
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Eight Golden Rules of Interface Design (1/3) Strive for consistency (the most frequently violated rule): Terminology Prompts Menus Help screens Color Layout Capitalization Fonts
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Eight Golden Rules of Interface Design (2/3) Let frequent users use shortcuts Abbreviations Special keys Hidden commands Macro facilities Offer informative feedback Design dialogs to yield closure Sequences of actions should be organized into groups Beginning, middle, and an end
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Eight Golden Rules of Interface Design (3/3) Offer error prevention and simple error handling Permit easy reversal of actions Support internal locus of control Reduce short-term memory load
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Effective navigation Clearly communicates Where am I? Where have I been? Where can I go?
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Navigation icons Should not require explanation Must represent the correct concept Must be visually distinct Are appropriately sized Text (label) is often the best visual cue
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Menus (1/2) Types Static, pull down, fly-out, pop-up Recognition, not recall (memory) Menu organization Alphabetical Chronological Categorical
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Menus (2/2) Provide real-estate savings But have invisible info Pull-down, fly-out Horizontal or vertical Pop up menus Appear at various places on the screen
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Bridging Gulf of Execution Hick’s Law : number of choices directly affects the size of the Gulf of Execution Fitt's Law : time required to acquire a target is a function of the distance to, placement of, and size of the target. How does this relate to navigation?
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KISS Remember each bit of info competes with other bits Eliminate irrelevant information
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From The Interface Hall of Shame http://www.iarchitect.com/tabs.htm What not to do!
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The Humane Interface “An interface is humane if it is responsive to human needs and considerate of human frailties.” Raskin, The Humane Interface (6) Requires knowledge of how humans and machines operate
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Object-Action Model of Interaction Understand tasks Evaluate real-world objects and the actions applied to those objects Create interface representations Objects and actions Make interface actions visible to users
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Task Hierarchies Computer system designers must generate a hierarchy of objects and actions (the interaction) that successfully models user tasks: Representations in pixels on a screen Representations in physical devices Representations in voice or other audio cue
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Semantic Understanding Understand how the process works, the meaning of an action A mouse click A submit button
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Syntactic Understanding Understand the specific rules of behavior that achieve an action In Windows, double-click on a file to launch (open) the application and load file On the Web, single-click an underlined word to go to a new Web page
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When Syntax Vanishes (1/2) We are forced to maintain a profusion of device-dependent details in our memory. Which action erases a character? Which abbreviations are permissible? Which of the numbered function keys produces the previous screen?
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When Syntax Vanishes (2/2) Learning, use and knowledge retention is hampered when details vary across systems unpredictably Syntactic knowledge is learned through repeated usage Syntactic knowledge is system dependent -- our visitors perceive “the Web” as a system, violate only after careful deliberation
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Our Job To minimize syntactic/memory burdens Familiar objects and actions represent their task objects and actions Standard (or de facto standard) widgets Why the mailbox did not work as early e-mail icon - not cross-cultural
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Five Tests of Effectiveness (1/2) Time to learn How long does it take for typical members of the community to learn relevant task? Speed of performance How long does it take to perform relevant benchmarks? Rate of errors by users How many and what kinds of errors are commonly made during typical applications?
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Five Tests of Effectiveness (2/2) Retention over time Frequency of use and ease of learning help make for better user retention Subjective satisfaction Allow for user feedback – interviews (focus groups), online surveys (both free-form comments and satisfaction scales).
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Design for Diversity Personality differences Cultural and international diversity Users with disabilities Elderly users Anything else?
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Raskin’s Rules The user should set the pace of the interaction Error avoidance, facilitated with “undo/redo” Accessible to the naïve, efficient for the expert
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Errors are not mistakes! Mistakes are the result of conscious deliberation Slips result from automatic behavior Norman’s Types: capture, description, data-driven, associative activation, loss-of- activation and mode errors
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Good Error Messages Polite Illuminating Treat the user with respect
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Design for Error Minimize occurrence by understanding the causes of errors Make detection and recovery easier Change the attitude toward error from “stupid user” to “stupid design”
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One small problem: When you design an error-tolerant system, people come to rely on that system (it had best be reliable!) Anti-lock brakes (ABS) Blade guard on circular saw Anything else?
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To increase errors, add a little: Social pressure Time pressure Economic pressure In other words, real life!
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Resultant design philosophy: Put knowledge in the world (iow,make options visible) Remember the three questions: Where am I, where can I go, where have I been? Design for errors
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The End! Apologies for the background noises as I advanced the slides in outline view … one take only and I don’t have Jyotsna’s production skills. :)
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