Models of the User

1
Models of the User

• CptS 443
• Human-Computer Interaction

2
Models of the User

• How do we account for the user in designing a
  user interface?
• User requirements models
• Determines user needs
• Human tech. requirements, organization
• Cognitive models
• Representations of the user
• Goal, linguistic, physical/device level

3
User Requirements Modelling

• How do we design usability, acceptability?
• Socio-technical methods
• CUSTOM
• OSTA
• ETHICS
• Soft systems methodology

4
CUSTOM

• User Skills and Task Match
• Stakeholder - affected by system
• Primary - users
• Secondary - receive output/provide input
• Tertiary - others affected
• Facilitating - developers, admins
• Examples
• Airline booking
• WSU payroll

5
CUSTOM Process

• How does CUSTOM model requirements?
• Describe organizational context
• Identify stakeholders
• Identify workgroups
• Identify task-object pairs
• Identify stakeholder needs
• Consolodate and check

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CUSTOM Analysis

• How do I find this info?
• What must the stakeholder achieve?
• Measures of success
• Sources of job (dis)satisfaction
• Knowledge/skills
• Attitude
• work
• computer technology

• Workgroup attributes
• Task characteristics
• frequency
• fragmentation
• choice of actions
• Issues
• responsibility
• security
• privacy
• Physical conditions

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OSTA

• Open Systems Task Analysis
• Specification of...
• ...technical aspects
• system functionality
• ...social aspects
• usability
• acceptibility

• Steps
• primary task
• In terms of user goals
• Input sources, forms
• External aspects
• Actions on objects
• Social system
• Technical system
• Satisfaction criteria

8
ETHICS

• Effective Technical and Human Implementation of
  Computer Systems
• Separate design teams
• technical
• social
• Merge results
• Steps...

• Problem identified
• objectives, tasks
• information needs
• satisfaction req.
• constraints
• Teams established
• needs prioritized
• Alternatives proposed
• Check compatibility
• Pairs ranked
• Detailed design

9
Soft System Methodology

• Organization
• Technology
• Human

• Stages
• Rich picture
• Root definitions
• Conceptual model
• Real world

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Rich Picture

• Detailed description of problem situation
• Contents
• Stakeholders
• Tasks
• Groups
• Organization and its processes
• Issues

• Building techniques
• Observation
• video recording
• audio recording
• Interviews
• Questionnaires
• Workshops
• role playing
• simulation
• critical incident analysis

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Root Definitions

• CATWOE
• Clients - output getters, beneficiaries
• Actors - users
• Transformations - changes in data
• How does input turn into output?
• Weltanschauung - world view, perception
• Owner - developers, admins
• Environment - systems world, influence

12
Participatory Design

• How can we involve the user in design?
• Improves work environment
• design work oriented, not system oriented
• Collaborative
• User is a member of design team
• Iterative
• User evaluates each stage of design

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Methods

• How do we communicate with the user?
• Brainstorming
• Withhold judgement
• Storyboarding
• Day-to-day activities, potential designs
• Workshops
• Designer queries user about work
• User queries designer about capabilities
• Pencil and paper exercises

14
Cognitive Models

• How do we represent the user when designing a
  user interface
• Goal/task hierarchies
• How we strategize to complete a task
• Linguistic models
• How we talk to the computer
• Physical/device models
• How we operate the computer

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Goal/Task Hierarchies

• How do users divide-and-conquer to solve
  problems?
• Granularity - scale of analysis
• unit task - no problem solving
• Models
• GOMS
• CCT
• Problems

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GOMS

• Goals, Operators, Methods, Selection
• Goals - what user wants to achieve
• memory point, evaluation
• Operators - primitive user actions
• Methods - how goal split into subgoals
• Not unique
• Select - Heuristic to choose method

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GOMS Example

• Goal Open-Help-System
• Select Goal Key-Method
• Press F1
• Goal Menu-Method
• Move-Mouse-To-Menubar
• Click-Mouse (on Help)
• Move-Mouse-To-Contents
• Click-Mouse
• Rule 1 Key-Method if Menu-Method fails

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GOMS Granularity

• Where do we start? When do we stop?
• Procedure
• Start single high level goal
• Decompose into sequence of unit tasks
• Decompose into primitive operators
• Focus on user
• Model user problem solving strategies
• Task analysis focuses on task

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CCT

• Cognitive Complexity Theory
• Expands GOMS with better prediction
• Parallel descriptions
• Users goals
• GOMS hierarchy
• Productions if condition then action, A?B
• Condition - working memory
• Action - motor response
• Device - transition network

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Problems

• Why doesnt this work?
• Post hoc
• Defined by the computer dialog
• Solution use manual from existing system
• Too rigid
• Missing necessary components like closure
• Solution flexibility

21
Linguistic Models

• How do users tell computers to perform tasks?
• BNF Backus-Naur Form
• task A B c d
• A,B - subtasks c,d - actions
• Task-action grammar
• Parameterized BNF
• Captures consistency
• fileop cmdop filename filename
  cmdop filename directory

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Linguistic Example

• Getting help
• get-help
• via-help-menu
• via-help-button
• via-help-func-key
• via-help-menu
• move-to-help click move-to-item click
• via-help-button
• move-to-button click
• via-help-func-key press-F1

23
Physical/Device Model

• What effort is required of the user to perform a
  task?
• Models
• MHP Model Human Processor
• KLM Keystroke Level Model
• Three-State Model

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KLM Operators

• K Keystroking (including shift, ctrl, alt)
• B Button pressing on mouse
• P Pointing a mouse
• H Hand moving between devices
• D Drawing
• M Mentally prep for physical action
• R System response (if significant)

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KLM Example

• Getting Help
• Operators
• H(mouse) - move hand to mouse (touchpad)
• PB - move pointer to Help and click
• M - read menu and find Contents and Index
• PB - move to Contents and Index and click
• Time
• .4 1.1 .2 1.35 1.1 .2
• equals 4.35 seconds