peterr@utcsrgv.UUCP (Peter Rowley) (08/24/83)
Thanks to Bob Cunningham for his review of the direct manipulation paper
by Shneiderman in the August '83 IEEE Computer magazine. I looked it up
today and found it enjoyable reading. It contains a persuasive argument
for the more widespread use of direct (non-linguistic, essentially) user
interfaces. The problems with direct manipulation are covered (p.64), though
perhaps with not enough depth, as some concluding examples of direct
manipulation systems seem to be poorly suited to their tasks.
On page 67, Shneiderman states:
"...a basic system [for bibliographic searching] could be built by first
showing the user a wall of labeled catalog index drawers. A cursor in
the shape of a human hand might be moved over to the section labeled
``Author Index'' and to the drawer labeled ``F-L.'' Depressing the button
on the joystick or mouse would cause the drawer to open up and reveal an
array of index cards with tabs offering a finer index. Moving the cursor
finger and depressing the selection button would cause the actual index
cards to appear. Depressing the button while holding a card would cause
copying of the card into the user's notebook also represented on the screen.
..."
Compare this with the (much simpler to program) interface which asks for a
function (say, search by author) and a parameter (author's name). It might
be fun to watch the graphics of the former system for the first few inquiries,
but the novelty would quickly wear off and one would be left with the arduous
task of locating the correct drawers and cards virtually manually. This
appears to be a case of a concrete metaphor taken to an extreme. The latter
system has a convenient concrete metaphor also, that of a helpful and efficient
librarian. I think we should always be willing to consider the "intelligent
agent" metaphor as opposed to a metaphor which involves inanimate objects.
Admittedly, one could not ask such a librarian for an opinion on the book,
but there are restrictions to all metaphors.
Later on the same page,
"Why not make airline reservations by showing the user a map and prompting for
cursor motion to the departing and arriving cities? Then use a calendar to
select the date, a clock to indicate the time, and the plane's seating plan
(with diagonal lines across already reserved seats) to select a seat."
I would have a hard time locating some of the cities I want to fly to on a
map of the US, though I know their names. Often, I DON'T NEED to know their
geographic locations; just that I have a meeting there next Thursday. Consider
also the practical problem of differentiating between closely spaced cities
or, worse, the multiple airports in NYC. And flipping through a graphic
calendar to select a date? Moving hands on a clock to select the time? Again,
consider the intelligent agent metaphor, this time a travel agent. The
agent is given the names of the cities involved, possible dates, and possible
times, and comes up with possible flights. A linguistic interface (such as
one would use with a real travel agent) allows one to express this necessary
uncertainty.
But, again, the paper is well-worth reading and includes a lot of insight as
to why videogames are popular and how their interfaces can be adapted to more
mundane tasks. Thanks again to Mr. Cunningham.
peter rowley, University of Toronto Department of C.S., Ontario Canada M5S 1A4
{cornell,watmath,ihnp4,floyd,allegra,ubc-vision,uw-beaver}!utcsrgv!peterr
{cwruecmp,duke,linus,decvax,research}!utzoo!utcsrgv!peterr