CS 407 Human Computer Interface

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CS 407 Human Computer Interface

• Class 27
• Wednesday, October 27, 1999

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Thought for the Day

• Any sufficiently advanced technology is
  indistinguishable from magic. Arthur C. Clarke

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A Modern Interface

• The cartoon that was on this page in class was
  found at Todays Cartoon by Randy Bergen.

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Todays Topics

• Finish Chapter 6
• Chapter 7
• 7.1, 7.2, 7.3
• Friday Chapter 8
• 8.1, 8.2, 8.3
• Skip almost all of chapter 9 10

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GOMS Notes

• Website
• http//www.usabilityfirst.com/goms/
• Critique GOMS is based on the human as an
  information processor responder
  Behavioralist psychology.

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Keystroke Level Model

• Six basic execution phase operators
• Physical motor
• K keystroking (also B button click)
• P pointing
• H homing
• D drawing
• Mental
• M mental preparation
• System
• R System response time

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KLM

• Times are empirically determined.
• Texecute TK TP TH TD TM TR

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KLM Example

• GOAL ICONISEWINDOW
• select
• GOAL USECLOSEMETHOD
• MOVEMOUSETOWINDOWHEADER
• POPUPMENU
• CLICKOVERCLOSEOPTION
• GOAL USEL7METHOD
• PRESSL7KEY

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KLM Example (2)

• Assuming hand starts on mouse
• USE-L7-Method

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KLM Example (3)

• USE-CLOSE-Method

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KLM Examples

• See text, page 250, 251.
• Compares Mouse and two differently mounted
  Trackballs.

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Three State Model

• Page 251-253
• Consider the states a mouse may be in
• Moving across the desktop, cursor moves on
  screen.
• Button pressed while moving, drags objects.
• State changes when button is pressed or released.

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Three State Model (2)

• Consider the states a light pen may be in
• Behaves like a mouse when touching the screen.
• Button pressed while moving, drags objects.
• State changes when button is pressed or released.
• 0. When pen is not on screen (3rd state!)

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Three State Model (3)
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Three State Model (4)
Touch screen
Button down
Button up
Remove pen
State 0
State 1
State 2
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Three State Model Implications

• Can calculate differences between mouse and light
  pen, or mouse and trackball.
• Fitts law coefficients are different for
  different tools.
• Why?
• Result table on page 253

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Chapter 7 Task Analysis

• Task decomposition
• Identify the subtasks, and the relationship
  between them.
• Knowledge-based techniques
• Look at what users need to know about the objects
  and actions for a task.
• Entity-Relation based analysis
• Identify actors objects and relationships
  between them and the actions they perform.

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Task Decomposition

• 0. Clean house
• Get vacuum out
• Get right attachment
• Clean rooms
• 3.1 Clean hall
• 3.2 Clean living room
• 3.3 Clean bedrooms
• Empty dust bag
• Put vacuum away

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Task Decomposition (2)

• Plan 0 do 1-2-3-5 in that order.
• do 4 when dust bag is full.
• Plan 3 do any of 3.1, 3.2, 3.3 in any order
• depending on which rooms need it.

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Alternative Plan 3

• Plan 3 do 3.1 every day
• do 3.2 once a week
• do 3.3 when company is coming

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Hierarchical Task Analysis

• Making a cup of tea (page 265)
• Exercise Using Figure 7.2 as a model, do a
  hierarchical task analysis for making a cup of
  coffee.
• You have 10 minutes.