Ch15: User Interface Design

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Ch15 User Interface Design

• Users often judge a system by its interface
  rather than its functionality
• A poorly designed interface can cause a user to
  make catastrophic errors
• Poor user interface design is one reason why many
  software systems are never used
• Graphics versus text
• Most business users interact with systems through
  GUIs
• Some legacy systems still use text-based
  interfaces
• This chapter
• key issues underlying user interface design, not
  implementation
• What makes a good UI? Examples of good and bad?

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GUI characteristics
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GUI advantages

• Easy to learn and use.
• Users without experience can learn to use the
  system quickly.
• The user may switch quickly from one task to
  another and can interact with several different
  applications.
• Information remains visible in its own window
  when attention is switched.
• Fast, full-screen interaction is possible with
  immediate access to anywhere on the screen

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15.1 UI design principles

• Familiarity
• Base the interface on user-oriented terms and
  concepts rather than computer concepts. For
  example, an office system should use concepts
  such as letters, documents, folders etc. rather
  than directories, file identifiers, etc.
• Consistency
• Display an appropriate level of consistency.
  Commands and menus should have the same format,
  command punctuation should be similar, etc.
• Minimal surprise
• If a command operates in a known way, the user
  should be able to predict the operation of
  comparable commands

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UI design principles

• Recoverability
• Provide some resilience to user errors and allow
  the user to recover from errors. E.g. undo,
  confirmation of destructive actions, 'soft'
  deletes, etc.
• User guidance
• Some user guidance such as help systems, on-line
  manuals, etc.
• User diversity
• Support interaction facilities for different
  types of user.
• For example, larger text for users who have
  seeing difficulties

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15.2 User-system interaction

• Two issues in interactive systems design
• Providing information from the user to the
  computer system
• Providing information from the computer system to
  the user
• Interaction styles
• Direct manipulation
• Menu selection
• Form fill-in
• Command language
• Natural language
• Give an example of each, strengths, weaknesses

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Multiple user interfaces
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15.3 Information presentation
Note separation of information from presentation
sw.
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Information display factors

• Is the user interested in precise information or
  data relationships?
• How quickly do information values change? Must
  the change be indicated immediately?
• Must the user respond to a change?
• Is there a direct manipulation interface?
• Is the information textual or numeric? Are
  relative values important?

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Analogue versus digital
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Dynamic information
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15.3.1 Color

• Color can
• help the user understand complex information
• highlight exceptional events
• Guidelines
• Design for monochrome then add color
• Don't use too many colors
• Use color consistently
• Avoid color pairings which clash
• Change color to show status change
• Be aware that color displays are usually lower
  resolution

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15.4 User support
E.g. on-line help, error messages, manuals
etc. Integrated with the user interface to help
users when they need information or make an error
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15.4.1 Error messages

• Poor error messages can mean that a user rejects
  a system
• Messages should be polite, concise, consistent
  and constructive
• The background and experience of users should
  determine message design

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Design factors in message wording
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Nurse input of a patients name
Please type the patient name in the box then
click ok
Bates
, J
.
OK
Cancel
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System and user-oriented error messages
User-oriented error message
System-oriented error message
?
Err
or 27
P
atient J
.
Bates is not registered
Clic
k on P
atients f
or a list of registered patients
In
v
alid patient id entered
Clic
k on Retr
y to re-input a patient name
mation
Clic
k on Help f
or more inf
or
OK
Cancel
P
atients
Help
Retr
y
Cancel
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15.4.2 Help system design

• Help? means help I want information
• Help! means HELP. I'm in trouble
• Both requirements have to be taken into account
• Guidelines
• Provide multiple entry points so that the user
  can get into the help system from different
  places.
• Indicate where the user is positioned in the help
  system.
• Allow the user to navigate and traverse the help
  system.

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Multiple entry points
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Help system windows
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15.4.3 User documentation

• Supply paper documentation as well as on-line
  information with a system
• Design documentation for inexperienced and
  experienced users
• Provide other easy-to-use documentation such as a
  quick reference card

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User document types
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15.5 User interface evaluation
The user interface design needs some evaluation,
but full scale evaluation is expensive. Ideally,
an interface should be evaluated against a
usability specification.
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Simple evaluation techniques

• Questionnaires
• Video recording of system use and subsequent
  tape evaluation
• Instrumentation of code to collect information
  about facility use and user errors.
• A button for on-line user feedback.
• Assignment wrt library
• Add user interface requirements to your spec
• Design the user interface. Include in a separate
  chapter
• Add help requirements to your spec
• Describe the library system help facilities.
  Include in a separate chapter