Information Technology Reference
In-Depth Information
these change and be in a better position to add to
or modify this set in the future.
We will examine the differing assumptions
that underlie desktop and mobile use under four
headings: the nature of mobile devices, the envi-
ronment of mobile infrastructure, the context of
mobile use and the purpose of mobile tasks. For
each we will examine the extent to which they are
reflected in the heuristics and, where appropriate,
how they may develop in the medium term.
'intelligent' system features can often get in the
way and it is often better to have simple consistent
interfaces. Of course this consistency is itself also
more important when descriptions of actions are
by their nature more parsimonious and Heuristic
3 focuses on this “consistent mapping between
user actions/interactions”. The balance between
consistency and intelligence changes as the input/
output bandwidth diminishes and the potential
annoyance of wrong adaptations may be less
problematic than the cost of doing everything by
hand. Note too that Heuristic 3 is as much about
external
consistency with the environment as
internal
consistency over time.
The overall small physical size is also central
to Heuristic 1's focus on losability/findability. A
small device can easily get lost both in public places
and in the home. However, its size means that it is
often kept close at hand, both allowing it to be used
as a proxy for the user in location services and also
meaning that it becomes a very personal device,
often used for private purposes. The importance of
privacy is picked up in Heuristic 1: “Since mobile
devices often get lost, adequate measures such as
encryption of data should be taken to minimize
loss” and Heuristic 7: “Make sure that users' data
is kept private and safe”. The personal nature is
also picked up in Heuristic 7: “Take aesthetic
and emotional aspects of the mobile device and
system use into account”. One of the unexpected
lessons that mobile phone manufacturers had to
learn quickly was that mobile phones are fashion
items as well as functional devices. In addition,
the content of mobile communications is often
very rich and personal.
The Nature of Mobile Devices
One of the most obvious differences between
mobile devices and fixed ones is size.
It has been pointed out that desktop screen
design is often lazy design—putting everything
on screen and letting the user worry about what is
important (Dix, 1999). In contrast, for the small
screen of a mobile device it is crucial that just the
right information and input options are available
at the right time—mobile device designers have
to think far more carefully about the user's task
than desktop designers. This is emphasized in
Heuristic 4 “since screen real estate is a scarce
resource, use it with parsimony. Dialogues
should not contain information that is irrelevant
or rarely needed.”; on a desktop application we
would (lazily) just show everything. This is also
reflected in Heuristic 2: “Enable the mobile user
to interpret the information provided correctly, by
making it appear in a natural and logical order”,
and in Heuristic 6: “Allow mobile users to tailor/
personalize frequent actions…”. While these are
both good advice for any interface it is particularly
important on a small screen to help deliver the
right information at the right time.
Several heuristics pick out issues of system
adaptation. The system should (Heuristic 1) “pri-
oritize messages”, (Heuristic 2) “… sense its envi-
ronment and adapt the presentation of information
accordingly”, (Heuristic 6) “suggest system-based
customization” and Heuristic 8 “Constructively
suggest a solution” for errors. In desktop systems
THE ENVIRONMENT OF MOBILE
Infrastructure
A key difference between driving across Africa
and driving across Europe is the different trans-
port infrastructure. The road system, signage,
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