Chapter 15 User Interface Design

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Chapter 15User Interface Design
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Interface Design
Easy to learn?
Easy to use?
Easy to understand?
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Interface Design
Typical Design Errors
lack of consistency too much memorization no
guidance / help no context sensitivity poor
response Arcane/unfriendly
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Types of Users(user may not be client)

• Novice
• Intermittent, experienced user
• Frequent Power user

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Interaction Modes

• Menu (icons?)
• Command Language
• Forms Fill-in
• Natural Language
• Voice recognition
• Dictionary of possible Fuzzy methods

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Natural Language(simple method)

• Obtain possible verb meanings from dictionary.
  Throw away those that are inconsistent with the
  verbs particle. (throw up, throw out, throw
  away)
• Find the thematic object among the
  preposition-free noun phrases. (before passive,
  after active verb)
• Throw away verb meanings inconsistent with
  thematic object. (shot rabbit, shot picture)
• For each remaining noun phrase determine thematic
  role (agent, instrument, etc.)
• Throw away verb meanings dictionary says are
  inconsistent with the thematic roles.

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Fuzzy Terms for Natural Language

• Fuzzy set has membership function with values
  from 0 to 1. Intermediate values allowed.
• Construct base sets over normal variable.
• Construct complex terms using and, or, not and
  qualifiers.

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Golden Rules

• Strive for consistency.
• Enable frequent users to use shortcuts.
• Offer informative feedback.
• Design dialogs to yield closure.
• Offer simple error handling.
• Permit easy reversal of actions.
• Support user-centered interaction
• Reduce short term memory load.

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Place the User in Control
Define interaction modes in a way that does not
force a user into unnecessary or undesired
actions. Provide for flexible interaction.
Allow user interaction to be interruptible and
undoable. Streamline interaction as skill levels
advance and allow the interaction to be
customized. Hide technical internals from the
casual user. Design for direct interaction with
objects that appear on the screen.
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Reduce the Users Memory Load
Reduce demand on short-term memory. Establish
meaningful defaults. Define shortcuts that are
intuitive. The visual layout of the interface
should be based on a real world metaphor.
Disclose information in a progressive fashion.
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Make the Interface Consistent
Allow the user to put the current task into a
meaningful context. Maintain consistency across
a family of applications. If past interactive
models have created user expectations, do not
make changes unless there is a compelling reason
to do so.
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Interface Design Activities
1. Establish the goals and intentions for each
task. 2. Map each goal/intention to a sequence
of specific actions. 3. Specify the action
sequence of tasks and subtasks, also called a
user scenario, as it will be executed at the
interface level. 4. Indicate the state of the
system, i.e., what does the interface look like
at the time that a user scenario is performed? 5.
Define control mechanisms, i.e., the objects and
actions available to the user to alter the system
state. 6. Show how control mechanisms affect the
state of the system. 7. Indicate how the user
interprets the state of the system from
information provided through the interface.
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On-line User Aid

• On-line help not as effective as paper manuals.
• All users have access
• Easily updated
• Experienced users find most useful
• Hypertext possible

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User Manuals

• Training manual shows how to accomplish tasks
• Basic reference manual simple descriptions of
  commands and features.
• Technical reference manual as much detail as
  possible.