Page 148 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Principles of Software Engineering

Notes module may not be having function cohesion. The heuristics are not written as hard and fast
rules; they are meant to serve as warning mechanisms which allow the flexibility of ignoring
the heuristic as necessary.
The main goal of heuristic evaluations is to identify any problems associated with the design of
user interfaces. Heuristic evaluations are one of the most informal methods. of usability inspection
in the field of human-computer interaction. There are many sets of usability design heuristics;
they are not mutually exclusive and cover many of the same aspects of user interface design.
Quite often, usability problems that are discovered are categorized—often on a numeric scale
to their estimated impact on user performance or acceptance. Often the heuristic evaluation is
conducted in the context of use cases (typical user tasks), to provide feedback to the developers
on the extent to which the interface is likely to be compatible with the intended users’ needs
and preferences.
The simplicity of heuristic evaluation is beneficial at the early stages of design. This usability
inspection method does not require user testing which can be burdensome due to the need for
users, a place to test them and a payment for their time. Heuristic evaluation requires only one
expert, reducing the complexity and expended time for evaluation. Most heuristic evaluations
can be accomplished in a matter of days. The time required varies with the size of the artifact,
its complexity, the purpose of the review, the nature of the usability issues that arise in the
review, and the competence of the reviewers. Using heuristic evaluation prior to user testing
will reduce the number and severity of design errors discovered by users. Although heuristic
evaluation can uncover many major usability issues in a short period of time, a criticism that is
often levelled is that results are highly influenced by the knowledge of the expert reviewer(s).
This “one-sided” review repeatedly has different results than software performance testing,
each type of testing uncovering a different set of problems.
6.11.1 Most-used usability heuristics for user interface design

Visibility of system status: The system should always keep users informed about what is going
on, through appropriate feedback within reasonable time.
Match between system and the real world: The system should speak the user’s language, with
words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow
real-world conventions, making information appear in a natural and logical order.
User control and freedom: Users often choose system functions by mistake and will need a
clearly marked “emergency exit” to leave the unwanted state without having to go through an
extended dialogue. Support undo and redo.
Consistency and standards: Users should not have to wonder whether different words, situations,
or actions mean the same thing. Follow platform conventions.
Error prevention: Even better than good error messages is a careful design which prevents a
problem from occurring in the first place. Either eliminate error-prone conditions or check for
them and present users with a confirmation option before they commit to the action.

Recognition rather than recall: Minimize the user’s memory load by making objects, actions,
and options visible. The user should not have to remember information from one part of the
dialogue to another. Instructions for use of the system should be visible or easily retrievable
whenever appropriate.
Flexibility and efficiency of use: Accelerators—unseen by the novice user—may often speed
up the interaction for the expert user such that the system can cater to both inexperienced and
experienced users. Allow users to tailor frequent actions.
Help users recognize, diagnose, and recover from errors: Error messages should be expressed in
plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

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