Scenarios of use
(Use cases)
Summary
Scenarios specify how users carry out their tasks in a specified
context. They provide examples of usage as an input to design,
and provide a basis for subsequent usability testing. They
are user- and task-oriented use cases.
Benefits
- It encourages designers to consider the characteristics
of the intended users, their tasks and their environment.
- Usability issues can be explored at a very early stage
in the design process (before a commitment to code has been
made).
- Scenarios can help identify usability targets and likely
task completion times.
- The method promotes developer buy-in and encourages a
user-centred design approach.
- Scenarios can also be used to generate contexts for evaluation
studies.
- Only minimal resources are required to generate scenarios.
- The technique can be used by developers with little or
no human factors expertise.
Method
An experienced moderator is recommended for the sessions
in which the scenario is explored.
- Gather together the development team and other relevant
stakeholders under the direction of an experienced facilitator.
- Identify intended users, their tasks and the general context.
This information will provide the basis for the scenarios
to be created by the development team.
- Functionally decompose user goals into the operations
needed to achieve them.
- Consider which activities should be performed by the user
and which by the computer.
- Create an outline of the users' activities, goals and
motivations for using the system being designed, and the
tasks they will perform.
- To maintain design flexibility, scenarios should not specify
what product features are used.
- Assign task time estimates and completion criteria as
usability targets.
- The session can be videotaped for later review or transcribed
for wider distribution.
- The results from scenario building sessions can be used
to plan user-based evaluations.
Practical guidelines
Try to generate scenarios to cover a wide range of situations,
not just the most common ones or those of most interest to
the design team.
Try to include problem situations that will test the system
concept, not just straightforward scenarios.
Work through the scenarios fully and judge the system on
that basis rather than trying to change the system half way
through.
More information
Scenarios are most useful when produced early in development
as specific realistic and detailed examples of what a user
would do, but without making any reference what user interface
features that would be used. See the examples.
Scenarios can also be used later to explore how the interface
would be operated.
Next steps
Use the scenarios as a basis for developing more specific
usability requirements.
Case studies
Background reading
The following books and web sites provide more information: |
