Chapter 9 Design guidance and design rationale

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Chapter 9Design guidance anddesign rationale
Adhering to principles and guidelines for good
UI design
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Sources of Design Guidance

• Standards
• User interface standard
• Design Guidelines
• Style Guide

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User Interface Standards

• Official, publicly available documents that
  define standards for user interface design
• ISO 9241 Ergonomic requirements for office work
  with visual display terminals
• ISO 14914 Software ergonomics for multimedia
  user interfaces
• ISO 13407 Human-centered design processes for
  interactive systems
• ISO 20282 Ease of operation of everyday
  products
• ISO International Organization for
  Standardization

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ISO 13407Human-Centered Design Processes for
Interactive Systems

• The human-centered approach
• Benefits
• Systems are easier to understand and use
• Discomfort and stress are reduced
• User satisfaction is improved
• Productivity and efficiency is improved
• Quality, aesthetics and impact are improved
• Also benefits developer, as this results in
  potential competitive advantage

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ISO 13407Human-Centered Design Processes for
Interactive Systems

• 4 Essential Elements of Human-Centered Design
• Active involvement of and clear understanding of
  users
• Appropriate allocation of functions between users
  and technology
• Specify functions users can perform
• Iteration of design solutions
• User feedback is critical
• Multidisciplinary design perspective
• Requires a variety of skills teams should have
  members with required skills, e.g.end users,
  purchasers, analysts,
• Next Style Guides

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Style Guides

• A typical guide includes
• Description of required interaction styles and
  user interface controls
• Covers both look (appearance) and feel (behavior)
• Guidance on when and how to use the various
  styles or controls
• Illustrations of styles and controls
• Screen templates
• Show how screens should (will?) look

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Commercial Style Guides

• Apple Interface Guidelines
• Microsoft Windows XP UI Guidelines
• IBMs Common User Access
• Motif Style Guide
• Sun Microsystems Java Look and Feel
• K Desktop Environment (Unix, Linux)

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Customized Style Guides

• Developed with the project in mind, culled from
  relevant portions of existing style guides.
• Helps focus on design issues early
• Enables use of principles and guidelines
• Steer decision making and serve as record
• Ensures consistency

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• Design Principles Simplicity, Structure,
  Consistency, and Tolerance
• Simplicity
• Structure
• Consistency
• Tolerance

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Simplicity
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Structure

• Organization of the UI in a meaningful way

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Structure

• Poor structure. Disjoint information that should
  be grouped together

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Consistency

• Uniformity in appearance, placement, and behavior

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Inconsistency

• Note button placement

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Tolerance

• Prevent user from making mistakes
• Prevention
• Recoverability
• Forward error recovery - system accepts the error
  and helps the user to accomplish their goal
• Backward error recovery undo the effects of the
  previous interaction
• Error messages should make clear to the user
• What has happened
• What the user should do
• Error messages should be clear, concise,
  positive, and constructive

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• Accessibility
• The Principles of Universal Design
• W3C Web Content Accessibility Guidelines
• Section 508
• The Limitations of Guidelines

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7 Principles of Universal Design

• Equitable use useful to diverse abilities
• Flexibility in use accommodates a wide range
• Simple and intuitive use easy to use learn
• Perceptible information communicates
  effectively
• Tolerance for error - minimizes
• Low physical effort minimum fatigue
• Size and space for approach and use

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W3c Web Content Guidelines

• W3c Web Content Accessibility Guidelines
• 14 general principles of accessible design
• Provide alternatives to auditory and visual
  content
• Dont rely on color alone
• Use markup and style sheets properly
• Clarify natural language usage
• Create tables that transform gracefully
• New technology pages transform gracefully

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W3c Web Content Guidelines

• Ensure user control of time-sensitive content
  changes
• Ensure direct accessibility of embedded user
  interfaces
• Design for device independence
• Use interim solutions (for older browsers to
  function)
• Use W3C technologies and guidelines
• Provide context and or entation information
• Provide clear navigation mechanisms
• Ensure that documents are clear and simple

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Section 508

• Federal Guidelines
• S/W must be accessible and usable by all federal
  employees, and members of the public with
  disabilities.

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• Design Rationale
• The Benefits of Recording Design Decisions
• Maintains decision process
• Valuable to justify design decisions
• How to Record Design Decisions
• Document only key decisions
• If in doubt, document!
• Tabular design is easiest to comprehend
• Yes, this is itself a UI
• Categorized by date