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The principles of good user interface design, including the gulfs of execution and evaluation, consistency, and object/action interface models. It also discusses the challenges of designing for open systems and introduces the concepts of knowbots and user modeling. The document concludes with a discussion on managing design processes, including organizational design, display design, color, and reading from paper versus displays.
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By Ben Shneiderman
Blaise W. Liffick Department of Computer Science Millersville University The following pages provide an instructor’s outline of Ben Shneiderman’s Designing the User Interface. In addition to providing useful lecture notes for instructors who want to use this as a textbook, these pages can be used as transparencies and/or projected during lectures. These notes were originally developed just as html files so that they could be used directly from the booksite that supports Designing the User Interface, 3rd^ Edition (http:// www.awl.com/dtui). Please direct comments about these notes to the booksite manager, Roger J. Chapman, at roger.chapman@acm.org
User Interfaces Are Products of Interdisciplinary Work - Who is Involved? o Psychologists o Graphic Designers o Technical Writers o Human Ergonomical Engineers o Anthropologists and Sociologists What are the Business Ramifications? o Overnight Success Stories - Netscape, America Online, Lycos o Intense Competition - Everyone vs. Microsoft o Copyright Infringement Suits - Apple vs. Microsoft (Windows ) o Mergers - Bell Atlantic and NYNEX o Corporate Takeovers - IBM's seizure of Lotus o International Liaisons - working relationship between MCI and British Telecom Individual User Level o Children can learn more efficiently o Pilots can learn to fly airplanes more effectively International Influences o Association for Computing Machinery - Computer Human Interaction special interest group has 6000+ members as of 1996 o ESPRIT Project in Europe devotes 150 person-years per year to research of user interfaces o Japan - Ministry of International Trade and Industry promotes commercial efforts among companies
Steps For User-interface Engineering
o High costs, reliability and effectiveness are expected o Length training periods are acceptable provide error-free performance o Subject satisfaction is less an issue due to well motivated users Retention via frequent use and practice
Physical abilities and physical workplaces There is no average user, either compromises must be made or multiple versions of a system must be created Physical measurement of human dimensions are not enough, take into account dynamic measures such as reach, strength or speed Account for variances of the user population's sense perception Vision: depth, contrast, color blindness, and motion sensitivity Touch: keyboard and touchscreen sensitivity Hearing: audio clues must be distinct Workplace design can both help and hinder work performance Cognitive and perceptual abilities cognitive process o short-term memory o long-term memory and learning o problem solving o decision making o attention and set (scope of concern)
o search and scanning o time perception factors affecting perceptual and motor performance o arousal and vigilance o fatigue o perceptual (mental) load o knowledge of results o monotony and boredom o sensory deprivation o sleep deprivation o anxiety and fear o isolation o aging o drugs and alcohol o circadian rhythms
Personality differences There is no set taxonomy for identifying user personality types Designers must be aware that populations are subdivided and that these subdivisions have various responses to different stimuli Myers-Briggs Type Indicator (MBTI) o extroversion versus introversion o sensing versus intuition o perceptive versus judging o feeling versus thinking Cultural and international diversity characters, numerals, special characters, and diacriticals Left-to-right versus right-to-left versus vertical input and reading Date and time formats Numeric and currency formats Weights and measures Telephone numbers and addresses Names and titles (Mr., Ms., Mme.) Social-security, national identification, and passport numbers Capitalization and punctuation Sorting sequences Icons, buttons, colors Pluralization, grammar, spelling Etiquette, policies, tone, formality, metaphors
Observing behavior Describing activity Conceiving of designs Comparing high-level concepts of two designs Training
Enable designers to compare proposed designs for execution time or error rates.
Predicting reading times for free text, lists, or formatted displays
Predicting keystroking or pointing times
Order on a complex set of phenomena Facilitate useful comparisons Organize a topic for newcomers Guide designers Indicate opportunities for novel products. 2.2.1 Conceptual, semantic, syntactic, and lexical model Foley and van Dam four-level approach Conceptual level: User's mental model of the interactive system Semantic level: Describes the meanings conveyed by the user's command input and by the computer's output display Syntactic level: Defines how the units (words) that convey semantics are assembled into a complete sentence that instructs the computer to perform a certain task
Lexical level: Deals with device dependencies and with the precise mechanisms by which a user specifies the syntax Approach is convenient for designers Top-down nature is easy to explain Matches the software architecture Allows for useful modularity during design
Goals, operators, methods, and selection rules (GOMS) model Keystroke-level model: Predict performance times for error-free expert performance of tasks Transition diagrams Natural GOMS Language (NGOMSL) Several alternative methods to delete fields, e.g. o Method 1 to accomplish the goal of deleting the field:
Norman's seven stages of action
Example: TAG definition of cursor control Dictionary of tasks: move-cursor-one-character-forward [Direction=forward,Unit=char] move-cursor-one-character-backward [Direction=backward,Unit=char] move-cursor-one-word-forward [Direction=forward,Unit=word] move-cursor-one-word-backward [Direction=backward,Unit=word] High-level rule schemas describing command syntax:
Follow simplifications made in higher-level, user-interface building tools. Potential benefits: Possible automatic generation of performance prediction A measure of layout appropriateness available as development guide Estimates generated automatically and amortized over many designers and projects o perceptual complexity o cognitive complexity o motor load Higher-level patterns of usage appear
Syntactic-semantic model of human behavior used to describe o programming o database-manipulation facilities
o direct manipulation Distinction made between meaningfully-acquired semantic concepts and rote- memorized syntactic details Semantic concepts of user's tasks well-organized and stable in memory Syntactic details of command languages arbitrary and required frequent rehearsal With introduction of GUIs, emphasis shifted to simple direct manipulations applied to visual representations of objects and actions. Syntactic aspects not eliminated, but minimized. Object-action design:
Decomposition of real-world complex systems natural human body buildings cities symphonies baseball game Computer system designers must generate a hierarchy of objects and actions to model users' tasks: Representations in pixels on a screen Representations in physical devices Representations in voice or other audio cue
E.g. A computer system: Interface Objects o directory
o Modern direct-manipulation systems o Familiar objects and actions representing their task objects and actions. o Modern user interface building tools o Standard widgets
Usage profiles Novice or first-time users Knowledgeable intermittent users Expert frequent users User characteristics Age Gender Physical abilities Education Cultural or ethnic background Training Motivation Goals Personality Task profiles Decomposition into multiple middle-level task actions, which are refined into atomic actions task frequencies of use matrix of users and tasks helpful Interaction styles Direct manipulation Menu selection Form fillin Command language Natural language
o Help screens o Color o Layout o Capitalization o Fonts o Most frequently violated
To reduce errors by ensuring complete and correct actions: Correct matching pairs Complete sequences Correct commands.
Organizing the display
computers constitute closed system human judgment necessary for unpredictable events o unanticipated situations o equipment failure o improper human performance o incomplete or erroneous data Knowbots or softbots: autonomous "agent" knows user's likes and dislikes makes proper inferences responds to novel situations performs competently with little guidance User modeling: keeps track of user performance adapts behavior to suit user's needs allows for automatically adapting system o response time o length of messages o density of feedback o content of menus o order of menu items o type of feedback o content of help screens can be problematic o system may make surprising changes o user must pause to see what has happened o user may not be able to predict next change interpret what has happened restore system to previous state Alternative to agents: user control, responsibility, accomplishment expand use of control panels o style sheets for word processors o specification boxes of query facilities o information-visualization tools
Design is inherently creative and unpredictable. Interactive system designers must blend knowledge of technical feasibility with a mystical esthetic sense of what attracts users. Carroll and Rosson design characterization: Design is a process, not a state. The design process is nonhierarchical. The process is radically transformational. Design intrinsically involves the discovery of new goals.
Guidelines documents and processes Each project has different needs, but guidelines should be considered for: Words and icons Terminology (objects and actions), abbreviations, and capitalization Character set, fonts, font sizes, and styles (bold, italic, underline) Icons, graphics, line thickness, and Use of color, backgrounds, highlighting, and blinking Screen-layout issues Menu selection, form fill-in, and dialog-box formats Wording of prompts, feedback, and error messages Justification, white space, and margins Data entry and display formats for items and lists Use and contents of headers and footers
Input and output devices Keyboard, display, cursor control, and pointing devices Audible sounds, voice feedback, touch input, and other special devices Response time for a variety of tasks Action sequences
Preparation o Understand organization policies and work culture. o Familiarize yourself with the system and its history. o Set initial goals and prepare questions. o Gain access and permission to observe/interview. Field Study o Establish rapport with managers and users. o Observe/interview users in their workplace and collect subjective/objective quantitative/qualitative data. o Follow any leads that emerge from the visits. Analysis o Compile the collected data in numerical, textual, and multimedia databases. o Quantify data and compile statistics. o Reduce and interpret the data. o Refine the goals and the process used. Reporting o Consider multiple audiences and goals. o Prepare a report and present the findings.
Controversial more user involvement brings o more accurate information about tasks o more opportunity for users to influence design decisions o a sense of participation that builds users' ego investment in successful implementation o potential for increased user acceptance of final system on negative side, extensive user involvement may o be more costly o lengthen the implementation period o build antagonism with people not involved or whose suggestions rejected o force designers to compromise their design to satisfy incompetent participants o build opposition to implementation o exacerbate personality conflicts between design-team members and users o show that organizational politics and preferences of certain individuals are more important than technical issues
Day-in-the-life scenarios: characterize what happens when users perform typical tasks can be acted out as a form of walkthrough may be used as basis for videotape useful tools o table of user communities across top, tasks listed down the side o table of task sequences o flowchart or transition diagram
Describe the new system and its benefits. Convey the high level goals of the new system. Identify the stakeholders. Identify specific benefits Address concerns and potential barriers. Anticipate changes in job functions and potential layoffs. Address security and privacy issues. Discuss accountability and responsibility for system misuse and failure. Avoid potential biases. Weigh individual rights vs. societal benefits. Assess trade-offs between centralization and decentralization. Preserve democratic principles. Ensure diverse access. promote simplicity and preserve what works. Outline the development process. Present and estimated project schedule. Propose process for making decisions. Discuss expectations of how stakeholders will be involved. Recognize needs for more staff, training, and hardware. Propose plan for backups of data and equipment. Outline plan for migrating to the new system.
Potential Controversies What material is eligible for copyright? Are copyrights or patents more appropriate for user interfaces?