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IMS417 UID
Chapter 1. Usability of Interactive Systems
1.
Introduction
 experimental psychology, computer science, graphic designers, human factors or ergonomics,
anthropologist, sociologists, technical writers
 HCI – User Interface
 ACM – SIGCHI
2.
Usability Requirements
 high-quality interfaces – usability, universality, and usefulness -- thoughtful planning, sensitivity to
user needs, diligent testing
 goals for requirements analysis
1. Proper functionality
2. Reliability, availability, security, and data integrity
3. Standardization, integration, consistency, and portability
4. Schedules and budgets
3.
Usability Measures
1.
2.
3.
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5.
time to learn
speed of performance
rate of errors by users
retention over time
subjective satisfaction
고려대학교 정보경영공학부
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4.
Usability Motivations
1. Life-critical systems – high reliability & effectiveness, lengthy training
2. Industrial and commercial uses – ease of learning, adaptation to local cultures, speed
of performance
3. Office, home, and entertainment applications – ease of learning, low error rate,
subjective satisfaction
4. Exploratory, creative, and collaborative interfaces
5. Sociotechnical systems
5.
Universal Usability
1. Variations in physical ability and physical workplaces
2. Diverse cognitive and perceptual abilities
3. Personality differences
 Carl Jung’s theories of personality types
 extroversion vs. introversion
 sensing vs. intuition
 perceptive vs. judging
 feeling vs. thinking
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5.
6.
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Cultural and international diversity
Users with disabilities
Older adults users
Designing for and with children
Accommodating hardware and software diversity
고려대학교 정보경영공학부
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2. Guidelines, Principles, and Theories
2.
Guidelines
 Shared language, terminology, appearance, action sequences
 Best practices
 Critics
 Too specific, incomplete, hard to apply, and sometimes wrong
 Proponents
 Encapsulate experience
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Navigating the interface
Organizing the display
Getting the user’s attention
Facilitating data entry
Principles
 More fundamental, widely applicable, and enduring than guidelines
 Need more clarification
1. Determine user’s skill levels
 “Know thy user” Hansen (1971)
 Age, gender, physical and cognitive abilities, education, cultural or ethnic background,
training, motivation, goals and personality
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 Design goals based on skill level
 Novice or first-time users / Knowledgeable intermittent users / Expert frequent users
 Multi-layer designs for learning
2. Identity the tasks
 Task Analysis usually involve long hours observing and interviewing users
 Decomposition of high level tasks
 Relative task frequencies
3. Choose and interaction style
Direct manipulation / Menu selection / Form fillin / Command language /
Natural language
4. Use the eight golden rules of interface design
5. Prevent errors
 better error messages – more specific, positive in tone, constructive
Correct actions
 graying out inappropriate menu items, selection rather than freestyle typing,
automatic completion
Complete sequences
 Single abstract commands
 Macros and subroutines
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6. Integrating automation while preserving human control
4.
Theories
 descriptive and explanatory – developing consistent terminology for objects and actions,
collaboration and training – information scent, taxonomy
 predictive – compare proposed designs for execution time or error rates
 motor-task performance predictions – predicting keystroking or pointing times (Fitts’ Law)
 perceptual -- predicting reading times
 cognitive – problem solving and understanding productivity (RT)
1. Levels of analysis theories (Foley et al., 1995)
 conceptual level; semantic level; syntactic level; lexical level
2. Seven stages of action (Norman, 1988)
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contribution by placing his stages in the context of cycles of action and evaluation
gulf of execution / gulf of evaluation
four principle of good design
the state and the action alternatives should be visible
there should be a good conceptual model with a consistent system image
good mappings that reveal the relationship between stages
continuous feedback
3. GOMS and KLM (Card et al., 1983)
 concentrate on expert users and error-free performance
 insufficient emphasis on learning, problem solving, error handling, subjective
satisfaction and retention
고려대학교 정보경영공학부
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Gulf of Execution – the mismatch between
the user’s intention and the allowable action
Gulf of Evaluation – the mismatch between the
system’s representation and the user’s expectations
고려대학교 정보경영공학부
IMS417 UID
고려대학교 정보경영공학부
IMS417 UID
고려대학교 정보경영공학부
IMS417 UID
3. Managing Design Process
2.
Organizational Design to Support Usability
 usability engineers, user-interface architects
 design (Carroll and Rosson, 1995)
 design is a process
 design process is nonhierarchical
 the process is radically transformational
 design intrinsically involves the discovery of new goals
3.
Three Pillars of Design
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3.
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Guidelines documents and processes
User-interface software tools
Expert reviews and usability testing
Development Methodologies
 user-centered design
 Logical User-Centered Interactive Design (LUCID) Methodology
envision  discovery  design foundation  design detail  build  release
5.
Ethnographic Observation
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Preparation
Field Study
Analysis
Reporting
고려대학교 정보경영공학부
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6.
7.
9.
Participatory Design
Scenario Development
Legal Issues
1.
2.
3.
4.
5.
privacy
safety and reliability
copyright or patent protection for S/W
copyright protection for online information, images, or music
freedom of speech in electronic environments
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4. Expert Reviews, Usability Testing
1.
Introduction
 the determinants of the evaluation plan
 stage of design (early, middle, late) □ novelty of project (well defined vs. exploratory)
 number of expected users
□ criticality of the interface
 costs of product
□ time available
 experience of the design and evaluation team
2.
Expert Reviews
 early or late in the design phase – formal report with problems or recommendations for changes
 half day to one week, lengthy training period required
 Heuristic evaluation / Guidelines review / Consistency inspection / Cognitive walkthrough / Formal
usability inspection
 3 to 5 expert reviewers
 bird’s-eye view approach
3.
Usability Testing and Laboratories
 speed up projects and cost savings
 controlled experiments vs. usability tests
 find flaws in user interfaces, fewer subjects, output report with recommendations
 task analysis  detailed test plan  pilot study
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 participants -- instructions, informed consent
 effective techniques -- think aloud / videotaping / discount usability engineering / field tests
 two limitations
 emphasizes first-time usage, limited coverage of the interface features
4.
Surveys
 clear goals in advance and development of focused items
 5-7 Likert scale / bipolar semantic differential
5.
Acceptance Tests
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Evaluation During Active Use
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Time for users to learn specific functions
Speed of task performance
Rate of errors by users
User retention of commands over time
Subjective user satisfaction
Interviews and focus-group discussions
Continuous user-performance data logging
Online or telephone consultants
Online suggestion box or trouble reporting
Online bulletin board or newsgroup
User newsletters and conferences
Controlled Psychologically Oriented Experiments
고려대학교 정보경영공학부
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6. Direct Manipulation and VE
2.
Examples of Direct-Manipulation Systems
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3.
Command-line vs. display editors vs. word processors
1. WYSIWYG
The VisiCalc spreadsheet and its descendants
Video games
Computer-aided design
Office automation
Discussion of Direct Manipulation
 principle of virtuality
 principle of transparency
 in harmony with the popular notions of logical symbolic sequential left-brain and the visual
artistic all-at-once right-brain problem-solving
 breaches the gulf of execution and the gulf of evaluation
1. Problems of direct manipulation
1. not an improvement over text for blind or vision-impaired users
2. spatial or visual representations can be too spread out
3. users must learn the graphical representations – icons
4. visual representation may be misleading
5. typing commands with the keyboard may be faster
6. choosing the right objects and actions may be difficult
고려대학교 정보경영공학부
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3.
4.
Visual Thinking and Icons
 an icon is an image, picture, or symbol representing a concept
 small representations of an object or action
 how to decide between icons and text, and how to design icons
 four levels of icon design (Marcus, 1992)
1. Lexical qualities
2. Syntactics
3. Semantics
4. Pragmatics
5. Dynamics
3D Interfaces
 the closer the interfaces are to the real world, the easier usage will be
 enhanced interfaces may be better than 3D reality
 a modest use of 3D technique (add highlights to 2D interfaces)  enjoyable, recognizable, and
memorable with improved use of spatial memory but visually distracting and confusing with additional
visual complexity
6.
Virtual and Augmented Reality
 immersive experiences, “looking at” to “being in”, telepresence aspect of virtual reality
 augmented reality
 multiple technologies for successful VE
 visual display / head-position sensing / hand-position sensing / hand-held manipulatives
 force feedback and haptics / sound input and output / other sensations / collaborative and
competitive virtual environments
고려대학교 정보경영공학부
IMS417 UID
고려대학교 정보경영공학부
IMS417 UID
7. Menu Selection, Form Fillin, and Dialog Boxes
2.
Task-Related Menu Organization
 hierarchical decomposition
 comprehensible and distinctive category
 categorical menu superior to alphabetical menu with the uncertainty about the terms
3.
Single menus
 binary menus, radio buttons
1. Pull-down, pop-up, and toolbar menus
 position constancy, keyboard shortcuts
 toolbars, iconic menus, and palettes
 pie menu (marking menu), flow menu
2. Menus for long lists
Scrolling menus, combo boxes, and fisheye menus
Sliders and alphasliders
Two dimensional menus
3. Embedded menus and hotlinks
4.
Combinations of Multiple Menus
1.
Linear menu sequences and simultaneous menus
고려대학교 정보경영공학부
IMS417 UID
2.
4.
5.
Tree-structured menus
 Depth versus breadth
 4 to 8 items per menu, but, at the same time no more than 3 to 4 levels
 breadth preferred over depth
Acyclic and cyclic menu networks
□ Getting lost – tree < acyclic < cyclic
□ Difficult to have mental model of the structure; backward traversal
Content Organization
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Task-related grouping in tree structures
 create groups of logically similar items
 form groups that cover all possibilities
 make sure that items are nonoverlapping
 use familiar terminology, but ensure that items are distinct from one another
Item Presentation Sequence
 time, numeric ordering, physical properties
 alphabetical sequence of terms; grouping of related items; most frequently used items first;
most important items first
 split-menu strategy
 adaptive menu (MS), adaptable (user-controlled) menu
Menu Layout
Titles
 single menus – simple descriptive title that identifies the situation
고려대학교 정보경영공학부
IMS417 UID
 linear sequence of menus – consistent grammatical style, brief but unambiguous noun phrases
 tree-structured menus
Phrasing of menu items
Graphic layout and design
 titles, item placement, instructions, error messages, status reports
 different fonts and typefaces
 linear sequence menus -- position marker
 GUI – tree structured or linear sequence menus -- cascading or walking menus
6.
Fast Movement Through Menus
 keyboard shortcuts, bookmarks, menu macros
7.
Data Entry with Menus: Form Fillin, Dialog Boxes, and Alternatives
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Form-fillin
2. Format-specific fields
3. Dialog boxes
Novel designs combining menus and direct manipulation
 control menus, marking menus, FlowMenu, toolglass
Audio Menus and Menus for Small Displays
1.
2.
Audio menus
 memorized, confirmation dialogs, repeat and exit the list, voice recognition (natural language)
Menus for small displays
 entertainment and information and communication services
 learnability – limit the number of functions – activated by hardware buttons
 soft keys, automatic Save function, concise writing and careful editing
고려대학교 정보경영공학부
IMS417 UID
고려대학교 정보경영공학부
IMS417 UID
고려대학교 정보경영공학부