Appropriating Heuristic Evaluation for Mobile Computing - Human-Computer Interaction and Innovation in Handheld, Mobile and Wearable Technologies - page 23

tions and requests for attention can happen
at inappropriate moments and that some
tasks may be interrupted. This raises two
kinds of problem: appropriateness of noti-
fications and recovery from interruptions.
• Privacy and security: Privacy issues be-
come more prominent. While staying mo-
bile, users find themselves in a variety of
spaces (private and public), in a variety of
situations (formal and informal), and in
a variety of infrastructures (wireless and
cable connection). Moving through these
settings means having different needs for
privacy and security.
• Intimacy and availability: Because mo-
bile devices are mobile, they are person-
ally available in a way that fixed devices
are not. Moreover, they seem to engender a
sense of being “personal” in a deeper sense
than desktop PCs (e.g., not just my PC but
my PDA and definitely my phone).

al. (1990) Rolf Molich and Jakob Nielsen initially
proposed a set of usability heuristics for the de-
sign of user interfaces. Aiming to maximize the
explanatory power of the heuristics, Nielsen later
refined them (Nielsen, 1994b), thereby deriving
the following set:

1. Visibility of system status: The system
should always keep users informed about
what is going on, through appropriate feed-
back within reasonable time.
2. Match between system and the real world:
The system should speak the users' 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.
3. 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.
4. Consistency and standards: Users should
not have to wonder whether different words,
situations, or actions mean the same thing.
Follow platform conventions.
5. 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.
6. Recognition rather than recall: Make ob-
jects, 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.
7. Flexibility and efficiency of use:
Accelerators—unseen by the novice user—

HEURISTIC EVALUATION

Introduction to Heuristic Evaluation

Heuristic evaluation (Nielsen et al., 1990; Nielsen,
1994b) is an inspection usability evaluation
method. In heuristic evaluation, experts scrutinize
the interface and its elements against established
design rules. The experts should have some back-
ground knowledge or experience in HCI design
and usability evaluation. Three to five experts are
considered to be sufficient to detect most of the
usability problems. The enlisted experts individu-
ally evaluate the system/prototype under consid-
eration. They assess the user interface as a whole
and also the individual user interface elements.
The assessment is performed with reference to
some usability heuristics. When all the experts are
through with the assessment, they come together
and compare and appropriately aggregate their
findings. In Molich et al. (1990) and Nielsen et