Design Activities in Usability Engineering laura leventhal and julie barnes

Reading   Chapter 7 in Protobook

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

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

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.

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

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

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.

Overview - Interaction Styles   The choice of interface style depends on   the type of user   the task   We have already learned this from Eason

Interaction Styles - Visual   Windowed Interactions   Menu-base Interactions   Virtual Reality

Interaction Styles - Visual   Direct Manipulation   Video Games

Interaction Styles - Verbal   Command line   Programming language   Natural language

Interaction Styles - Manipulable, Non-visual (Advanced?)   Haptic   Multimodal   Multimedia

General Design Guidelines   During the design of any interaction, there are a few general design guidelines

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

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.

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”

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 metaphor’s suggested use and the ability of he computer to support and extend the metaphor.

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!

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.

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.

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 user’s 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 user’s mental model.

Let the user be in control   Allow the user to accomplish tasks quickly and reliably.   It is important to provide direct paths to user’s goals.   Allow users to recover from errors.   Encourage the user’s perception of stability.   Accommodate users with different levels of expertise and experience.