MAS.632 Conversational Computer Systems - MIT OpenCourseWare

BdcSod hDiver
Inmeroclive Voie Rponse 121
The output of the Describer is the text description of a "tour," an example of
which follows.
"Ifyour car is parked on the same side of the street as 20 Ames Street, turn around and
start driving. Drive all the way to the end and take a left onto Memorial Drive. After
about one quarter of a mile, take the easy left and merge onto Main Street. It becomes
the Longfellow Bridge. After you cross the bridge you will come to a rotary. Go about
three quarters of the way around it, and turn onto Charles Street. Merge with Storrow
Drive."
The text ofthe tour must be recited by a speech synthesizer; this is done by the
Narrator. It is the Narrator's responsibility to recite the tour at a rate that allows
the user to write down the directions. Unfortunately people write directions at
greatly varying rates; some have elaborate shorthand notations and can record
the directions quickly, while others write them word-by-word. The Narrator's
only recourse is to pause between each part of the route and wait for touch tone
input from the user as a flow-control mechanism, but this does not make for a
very comfortable interface. More graceful flow control requires spoken feedback
from the direction recipient; an attempt at this is described in Chapter 9.
Back Seat Driver is a subsequent Media Lab project that also employs speech
synthesis for direction giving but in the very different context of operating in a
car in real time while the user is driving. Although much of the software from
Direction Assistance proved useful to this project, Back Seat Driver is different in
two respects. First is the motivation to use voice because a driver's eyes are busy
watching the road, whereas Direction Assistance focused on remote telephone
access. This raises the issue of how to instill user confidence in a system that cannot
be seen and speaks only when necessary. Second is the real-time nature of
Back Seat Driver; it must know when to speak, how long it will take to say an
utterance, and detect when the driver has made a mistake.
Back Seat Driver utilizes a vehicle navigation system to report the automobile's
position, speed, and, direction to the route planner.' This navigation system uses
an inertial guidance system in combination with the constraints provided by the
map database (which is stored on CD-ROM) to determine position; for more discussion
of the various location determining technologies, see [Davis 1989]. Route
planning and discourse generation are done by software running on a computer
in the trunk speaking via a speech synthesizer connected to one of the serial ports
of the computer (see Figure 6.7).
The initial task of the Back Seat Driver is identical to that of Direction Assistance,
namely, to elicit the destination from the driver (the current position of the
'The vehicle navigation system was built by the project's sponsor, Nippon Electric
Company.