Variety of Application Areas
User-interfaces, and the underlying applications, may need to be very
different for very specific application areas:
- Life-critical systems
The absolute priority is error-avoidance.
Lengthy training periods and high cost are acceptable.
User-friendliness is less important than safety.
This may for instance imply that confirmations for dangerous actions
are needed to avoid starting these actions by mistake.
Typical examples are: air-traffic control, medical systems, nuclear power plants.
An extreme example is the user-interface for launching nuclear missiles,
which includes two people having to perform the same action (like turning a
key) simultaneously, just to avoid any one person from accidentally
launching a missile by mistake.
Note: although highly placed officials often claim that human
life has no price tag (or an infinite price) reality is that budget cuts
are made at the expense of human lives. The FAA reactions to the
AA flight 800 disaster have recently proven this point.
- Industrial and commercial systems
These systems include banking, insurance, order entry, airline, hotel
and car rental reservations, etc.
Lower cost may be preferred over high reliability, user-training
should be minimal, and speed is important.
The tradeoffs for speed of performance, error rates (and the involved
potential damage) and development cost are governed by the total cost
over the system's lifetime.
- Office, home and entertainment applications
Applications like word processing, automated transaction machines,
information retrieval, video games, email, etc. are available from
a variety of vendors, in different flavors.
Subjective satisfaction, low cost, and ease of learning are most important.
Until some time ago low error rates were also important,
but the reality is that people are getting used to error-prone software.
Another complicating factor is that people often make very simple use
of software and would be helped by a rather restrictive user-interface,
but when buying software they look for long lists of features they will
never use.
- Exploratory, creative and cooperative systems
World Wide Web, groupware, workflow management and other systems have
entered the marketplace, and support the user's desire for more and more
information, for communication and for collaboration with others.
Users are knowledgeable in their task domain, but novices in these
novel computer concepts.
These systems are difficult to design.