OPINION THE WAY I SEE IT

ent computer, should a flicked object move from one computer to the other? And if so, how can the sender also retain a copy? (Note that systems that have faced—and created answers to—these issues have existed for quite some time.)

The problems faced by gesture developers remind me of similar issues that arose during the early days of development of the GUI. Thus, in the development of the early Xerox PARC systems, when one moved the icon of a file across the screen to a file folder, it was natural that the icon would disappear into the folder. Similarly, when a file was moved to the trash, it was natural that the icon— and the file—disappeared from sight. But this movement principle got into trouble with the printer: Moving the file to the image of the printer caused the item to be printed, but it also caused it to disappear from the screen. Much rethinking took place then. Much rethinking is required now.

The proper behavior for mov-
ing something to a printer is
obvious: The object should
remain in view. What if the
movement is to an external
storage device or a different
computer? Today, the file stays
on the home computer as well.
This difference in end result
depending upon the nature of
the destination is the source of
continual confusion for some.
What gesture signifies copy
rather than move?
Some systems are trying to
develop a gestural language,
sometimes with the number of
touch points as a meta-signal
about the scope of the move-
ment. A single finger gesture
means one thing, the same
gesture with two fingers means
another, yet another with three
or four. But note the existing
failure of attempts to use mul-
tiple mouse clicks in this way. A
single mouse click points, a dou-
ble mouse click selects a word,
a triple mouse click selects a
paragraph. But if each addi-
tional click moves up one level
in the hierarchy, shouldn’t three
clicks select the sentence? How
well known and followed is that
triple mouse click? Note that the
early developers of the Xerox
Star computer spent consider-
able effort and time to develop
a systematic clicking language;
although some of their efforts
survived, much was lost.

Ballmer, S. “CES 2010: A Transforming Trend—The Natural User Interface.” The Huffington Post, Jan. 12, 2010, from http:// www.huffingtonpost. com/steve-ballmer/ces- 2010-a-transforming- t_b_416598.html/ Buxton, B. “Multi-Touch Systems that I Have Known and Loved,” available from http:// www.billbuxton.com/ multitouchOverview. html/ Krueger, M. W. Artificial Reality. Reading, Mass.: Addison-Wesley, 1983.

Myers, B. A. “A Brief
History of Human
Computer Interaction
Technology.” interac-
tions 5, 2 (1998): 44–54.
http://www.cs.cmu.
edu/~amulet/papers/
uihistory.tr.html/
May + June 2010