Why Human-Computer Interaction?
To frame our discussion, consider:
What role does the user interface have in system development?
Should there be a prominent role for HCI in system development and what would justify that role?
The high-end Xerox copier contains 30+ microprocessors linked together in a local
area network. They monitor the operations of the machine allowing modifications of operational parameters.
Operators are provided information during work to facilitate task performance. This monitoring
includes the ability to "reason" about machine functioning and predict breakdowns. Once a breakdown is
predicted the system notifies the local service provider.
Reported in RISKS Digest,
Capt. Zdravko Beran told Coast Guard investigators on the first day
of testimony before a board of inquiry. ``He told me that
(navigational) light was dead ahead and then he wanted to turn
a few degrees to the port (left).''
Instead, the officer, Zvonko Baric, turned the ship to the
right, or starboard, causing it to run aground on sensitive
coral in the Fort Jefferson National Monument, Beran said.
The steering mechanism must be turned in the opposite
direction of the intended course -- the reverse of how most
such devices operate, Beran said.
Reported in RISKS Digest, 13(7)
During the development of aircraft in WWII certain planes experienced a number of accidents. The control mechanism for the landing gear had a lever in the cockpit which up, the landing gear was down. The manufacturer switched this mechanism so that lever down=landing gear down.
Reported in RISKS Digest, 18(68)
From the San Francisco Chronicle (Dec 14, 1996).
According to [Deputy Chief]
Gamble, a dispatcher -- alerted to the waterfront fire at 2:48 p.m. --
initially sent only four pieces of equipment by computerized message when he
should have sent seven. Gamble said the dispatcher mistakenly entered into
the computer that the alarm had come from a street box, triggering a
relatively minimal first response. The second error occurred when the first
units at the scene immediately called for help. At that point, Gamble said,
the dispatcher told the computer to send the next wave -- only to discover
six minutes later that the units never got the message. Gamble explained
that because the dispatcher gave the computer the wrong message on the first
alarm, the computer wouldn't accept the second." [...]
The RISK seems to be a user interface that makes it too easy to make
mistakes entering data, and "business rules" that assume that whatever was
previously entered into the computer is correct.
Reported in RISKS Digest, 16(49)
The bank that I used switched over from one version of ATM software to
another. In the old version you had to enter your PIN, then press a
special key to get the ATM to accept it.
Somebody decided that this was a waste of effort, since all the PINs were
the same length, so the machine could tell when you were done. Therefore,
they removed the extra keystroke.
This might have been fine except for what they did with that key. It became
a selection of what you wanted to do. Unfortunately, it became the Fast
Withdrawal button, which takes a fixed amount of money out of checking,
without any more chances to stop it.
Reported in RISKS Digest, 17(37)
A SpaceCom technician at their uplink facility in Tulsa, Oklahoma accidentally send out a spacey command shutting down
the satellite receivers used by pager systems throughout the country, affecting millions of pagers. SpaceCom supports 5 of
the largest 10 paging outfits. This happened at 1 a.m. yesterday, and each receiver had to be manually reprogrammed --
which took all day until most of the service could be restored. Al Stem, VP and GM of SC said, "This hasn't ever
happened before. And we're putting additional systems in place to make sure it never happens again." [Source: AP report,
seen in the San Francisco Chronicle, 27 Sep 1995]
A new maths related bug has now surfaced in another Microsoft product. Type or paste 1.40737488355328 into a cell in a
copy of Microsoft's Excel spreadsheet and you will be rewarded, not with the number you expect but with 0.64 ( unless you are on a Macintosh where 1.40737488355328=1.28). If you perform arithmetic with this it will act as if 0.64 had been entered so it is not simply a display error. When the number is
used as part of a formula the error is not apparent. Portability?
NOTE: If you type =2*1.40737488355328 you get 2.814749767. If you then copy that cell and paste it as a value you get 2.56.
This error is apparently fixed in the version of Excel appearing with Office 97 for PC.
In the late 1980s NYNEX
proposed replacing current workstations with new, ergonomically
designed stations for certain operators (the ones that answer
when 0 is pressed). The older stations were character oriented
displays. The proposed stations were graphical, high-speed, high
resolution units. The workstation manufacturer claimed a 2
second speed advantage per transaction over the older workstations. A field
trial comparing the two workstations showed that the proposed
workstation was slower by .8 of a second on the average (this
translates in to $2.4 million a year in additional operating
costs).(Gray, CHI'92)
Reported in RISKS Digest, April 1993
A Dutch chemical factory was heavily damaged and three people
killed from an explosion. The damage was estimated at millions
of guilders. The accident was the result of an operator typing
the incorrect tank number. The operator, employed for three
months and still in training, forgot to check if the contents of
the tank were consistent with the recipe.
Myers and Rosson (CHI'92) present data on percentage of code
that goes into development of the interface. The survey incorporated data
from 74 projects ranging from 400 to 5,000,000 lines of code over a variety
of languages and application types.
- average - around 48% of the code is interface
- 44.8% of design time
- 50.1% of implementation time
- 37% of maintenance time devoted to UI
Competition, advertising, users groups, word-of-mouth!!
Reported in RISKS Digest, 13(7)
There's a great tendency to fix poor interfaces by training, in the industry. The majority of a transition program, for example, is devoted to keyboarding on the flight management system, at the expense of basic skills. Indeed, there's a trend
to shorten training programs, not expand them. In highly automated
cockpits, there is also a well-recognized problem of the pilot being too
far out of the loop; however, manufacturers do not seem inclined to change
current design practices.
- HCI is not part of the traditional(?) education program for software developers.
Sommerville (4th ed., p. 4) Well engineered software has the
following characteristics:
- functional
- maintainable
- reliable
- efficient
- offer an appropriate user interface
The terminal and the end-user what's the difference.
Much is left for programmer's intuition.
User expectations have changed in the last few years!!!
Competition, advertising, no longer can we follow the guru path!!
"Having trained, qualified HI people involved in a software
effort produces major benefits at a most reasonable cost."
(Tognazzini)
Bailey (CHI'93) shows that HCI specialists create
interfaces that have fewer errors and supported faster user execution than interfaces designed by programmers.
Jefferies (CHI'91) compared four strategies
for evaluating the interface for a product. HCI professionals
using heuristic evaluation, usability testing (HF), guidelines (SE),
cognitive walkthrough (SE).
Errors Found by Technique
| Heuristic | usability | Guidelines | Cognitive Walkthrough |
| 100% | 97% | 37% | 86% |
Time spent on analysis (person-hours)
| Heuristic | usability | Guidelines | Cognitive Walkthrough |
| 20 | 199 | 17 | 27 |
