Design Activities in Usability Engineering

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Design Activities in Usability Engineering

• laura leventhal and julie barnes

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Reading

• Chapter 7 in Protobook

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Overview

• Topics
• Design Process
• Interaction Styles Overview
• Design Issues for Individual Interaction Styles
• Using Standards and Guidelines
• Design of Interface
• Predictive assessment of Interface Design
• Prototyping as a Design Strategy and Prototyping
  tools
• Reading Reference
• Chapters 7 - 12

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Design Process in Usability Engineering

• Design of Interaction
• Design of Interface
• Both design activities
• are driven by the specification
• occur at a high and low level

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Design of Interaction

• Design of the interaction is concerned with
• the design of the overall "look and feel" of the
  UI
• the design of individual interactions
• High level design activities
• focus on the selection of an interaction style
• selection of the general pattern of interaction
• Low level design activities
• design of individual interactions
• design decisions include
• choice of content and arrangement of menu
  options, selection of button types, selection of
  background colors and so on.

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Design of the Interface

• Design of the interface is concerned with
• design of the actual software that will drive the
  UI
• Designing the interface is really just a software
  design problem.
• High level design activities
• select overall architecture for the software
  (overall pattern of procedure calls, assignment
  of workload and distribution of communication)
• Low level design activities
• design of classes, member functions, data
  structures and data members, and other

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Interaction Styles

• A central issue in User Interface Design
• For many, interaction styles and designing an
  interaction style is the issue of HCI

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Basic Definitions

• Interaction or Dialogue Style
• How a user interacts with a computer system.
• The concept of style is central to our ability to
  characterize and understand the diversity of
  interactive systems.
• The categorization of a particular interface into
  a particular style is often fuzzy however.

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Overview - Interaction Styles

• The choice of interface style depends on
• the type of user
• the task
• We have already learned this from Eason

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Interaction Styles - Visual

• Windowed Interactions
• Menu-base Interactions
• Virtual Reality

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Interaction Styles - Visual

• Direct Manipulation
• Video Games

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Interaction Styles - Verbal

• Command line
• Programming language
• Natural language

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Interaction Styles - Manipulable, Non-visual
(Advanced?)

• Haptic
• Multimodal
• Multimedia

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General Design Guidelines

• During the design of any interaction, there are a
  few general design guidelines

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Here are Some General Guidelines

• Facilitate the development and use of workable
  mental models
• Use meaningful analogies and metaphors
• Avoid anthropomorphism
• Minimize modal interactions
• Reducing the cognitive (mental) workload on the
  user
• Let the user be in control

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Facilitate the development and use of workable
mental models

• Present the interaction consistently across
  actions and terminology.
• Allow the user to build a mental model of the
  system based on the tasks that they actually
  perform with it rather than what the system
  actually does.

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Facilitate the development and use of workable
mental models(2)

• The interface should guide new users through
  normal and reasonable patterns of usage.
• Experts often times have good models and do not
  need the sophisticated protection mechanisms that
  novices do.
• Congruence. Words and objects should be used in
  the same ways throughout the interface.
• Clear landmarks and directions enhance
  wayfinding

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Use Meaningful Analogies and Metaphors

• Choose a concrete metaphor with limited
  interpretation.
• Choose a metaphor that is appropriate to the task
  and the user. For example, choose a familiar
  metaphor for novice or first-time users.
• From Apple Computer, Inc. (1992, p. 5)
• Try to strike a balance between the metaphors
  suggested use and the ability of he computer to
  support and extend the metaphor.

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Avoid Anthropomorphism

• The word anthropomorphism means to assign human
  characteristics to an inanimate or non-human
  entity.
• If you build an anthropomorphic interface, a
  reasonable interpretation by the user may be that
  the interface is saying,
• I am a salient being, I am like you.
• The user may then expect the interface to respond
  in a number of human ways that are not supported.
• Anthropomorphism is bad and should be avoided!

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Minimize Modal Interactions

• Modality is defined as a set of user actions that
  has a different outcome in one context than in
  another.
• Avoid modal interactions whenever possible.

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Reducing the cognitive (mental) workload on the
user

• When users develop mental models of systems, the
  characteristics of the interface can influence
  their "cognitive" or mental workload in
  constructing the model.

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Reducing Cognitive Workload (2)

• Present options clearly and explicitly and avoid
  presentations that include multiple reasonable
  interpretations.
• It is possible to mask the meaning or importance
  of interface elements by drawing the users
  attention to superfluous interface elements. .
• Allow users to use semantic (as opposed to
  syntactic) knowledge as much as possible.
• Reduce the number of cognitive transformations or
  translations from the interface to the users
  mental model.

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Let the user be in control

• Allow the user to accomplish tasks quickly and
  reliably.
• It is important to provide direct paths to users
  goals.
• Allow users to recover from errors.
• Encourage the users perception of stability.
• Accommodate users with different levels of
  expertise and experience.

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