🚀 go-pugleaf

I would like to comment on one part of Randy Ivanciw's letter about
the need for an integrated environment for workstations. (Which I
believe much of the world is coming around to endorsing even if they
do not know how to do).

Randy gives the example where one is reading a mail inbox and gets a call
on the phone. It would be very useful to be able to drop the mail, pick
up the phone, answer the call, and then return to one's mail.

With iconographic systems (such as STAR or SMALLTALK-80) this would be
quite simple. One would use the mouse to drag the cursor away from
the current icon (be it editor window, mail inbox, virtual terminal)
and position the cursor to the telephone icon. There one would
expand the telephone icon and answer the phone. Later one could return
to the old mail inbox icon.

However, there is a problem here that several Human Factor's people
have pointed out. That is, one could easily have quite a few "pushed"
windows, each one deep in some command dialog. The Human Factor's
people have pointed out that humans have a real scarcity of short
term memory (about 4-7 chunks). Clearly, we humans are going
to have a real problem understanding what was going on in our
workstations after a couple of interruptions.

Therefore, I would like to propogate, to designers of workstations,
a user interface folk theorem that I heard recently: NEVER HAVE
MULTIPLE LEVELS OF STATE ENCODED INTO A DISPLAY.

Naturally, I am curious as to what others feel this restriction will
do to programming a user interface. I would also be interested in
collecting other folk theorems.

					- Steven Gutfreund