User Interfaces

1
User Interfaces

• Introduction to Engineering Designs of
  Interfaces
• Part I.

2
Overview

• Usability-based design
• System Acceptance
• Product development lifecycle
• Model of user and task
• Usability testing

3
References

• Bruce Tog Tognazzini  
• Tog on Software Design
• http//www.asktog.com/basics/firstPrinciples.html
• Alan Cooper About Face The Essentials of User
  Interface Design
• http //www.uidesign.net/2000/interviews/cooper1.h
  tml
• http//www.uidesign.net/newpapers_index.html
• Don Norman Design of Everyday Things
• Jakob Nielsen
• Designing Web Usability
• Usability Engineering
• Edward Tufte Visual Explanations
• Vincent Flanders and Michael Wills Web Pages
  that Suck

4
Attributes of System Acceptability
Easy to learn
Utility
Social
System Acceptability
Efficient to use
Usability
Practical
Easy to remember
Cost
Compatibility
Few errors
Reliability
Fun to use
Other
Adapted from Nielsen, 1993
5
Learnability

• Measurement Task performance as a function of
  time/effort
• Practice Exploratory learning useful guidance

Focus on Expert
Performance
Focus on Novice
Time or Number of Attempts
6
Efficiency

• Measurement Task performance of expert users
• Practice Effects of system complexity

Focus on Expert
Performance
Focus on Novice
Time or Number of Attempts
7
Memorability

• Measurement Task performance of casual users
  Practice Exploratory learning useful reminders

Focus on Expert
Performance
Focus on Novice
Time or Number of Attempts
8
Errors and Recovery

• Definition Actions that fail to accomplish
  desired goals
• Measurement Recording of errors in realistic
  task environments
• Type of errors and recovery
• System error
• User errors designer errors?
• Fail operational
• Catastrophic errors

9
Technology vs Product Design
Technological Innovation
Solution Product
Businessman
Problem Definition
10
Users and Customers

• Different knowledge
• Different motivation
• Good idea User-centered design

11
Principles of a User Centered Design

• An early focus on uses and tasks
• Empirical measurement of product usage
• Iterative design whereby a product is designed,
  modified and tested repeatedly

12
Product Development Life Cycle

• User and usage needs analysis
• Specification of requirements
• Preliminary high-level, conceptual design
• Detailed design design review
• Product - prototype implementation
• Usability testing
• Iterative design modifications
• Alpha / Beta Testing
• Product Release

13
Needs Assessment

• Identify and characterize target user population.
  
• Identify and analyze user tasks
• Identify users' physical, organizational, and
  cultural environment.
• Identify usability problems on similar or
  existing product.
• Identify initial users' product feature list.