Information Technology Reference
In-Depth Information
maintain, and minimally reliant on system resources. Design metrics, which
measure can be used to evaluate aspects such as the interface, architecture, indi-
vidual, and even individual components, aid the developers in achieving such
software goals. Constant re-evaluation and revision throughout the design process
using design metrics will prevent the need for major revisions down the road.
12.3.1 Interface
While important to the success of a piece of software, the user interface is often
times very difficult to measure in terms of usability. Evaluation of the user
interface is important, though, and should be included in the assessment of
software.
Design metrics can be devised to assess software's usability as it pertains to
specific quality factors like those defined by ISO 9126, such as learnability or
operability. You may, for example, set a specification for the exact amount of time
it should take a user to complete a task or operation in the software. Once these
standards are specified, users can be observed and surveyed during and after use of
the software to gather numerical data to compare to specified metrics. Sommerville
describes some common methods for evaluating the user interface (Sommerville
2004
):
• Questionnaires to collect information regarding the users' opinion of the user
interface.
• Recording user interaction with the software via video equipment.
• Observing the users as they interact with the software and ''think aloud.''
• Implementing code to collect data regarding feature use and error commonality.
While metrics exist to measure usability without direct interaction with users,
Pressman suggests that user preferences and opinions are most important. He
quotes Nielson and Levy as reporting that ''one has a reasonably large change of
success if one chooses between interface [designs] based solely on users' opin-
ions'' (Pressman
2005
).
12.3.2 Web Design Evaluation
Still a relatively new topic, design metrics for the Web are much more qualitative.
To
be
useful,
metrics
for
Web
design
should
answer
questions
such
as
(Sommerville
2004
):
• Is usability promoted by the interface?
• Is the application pleasing to the user?
• Does the design provide the most information with the least effort?
