he ability to access information
on demand at any location confers competitive advantage on
individuals in an increasingly mobile world. As users become
more dependent on this ability, the span of access of data
repositories will have to grow. The increasing social accep-
tance of the home or any other location as a place of work is
a further impetus to the development of mechanisms for
mobile information access.
These considerations imply that data from shared file sys-
tems, relational databases, object-oriented databases, and
other repositories must be accessible to programs running on
mobile computers. For example, a technician servicing a jet
engine on a parked aircraft needs access to engineering
details of that model of engine as well as past repair records
of that specific engine. Similarly, a businessman who is contin-
uing his work on the train home from Manhattan needs access to
his business records. Yet another example involves emergency
medical response to a case of poisoning: the responding per-
sonnel will need rapid access to medical databases describing
poison symptoms and antidotes, as well as access to the spe-
cific patient’s medical records to determine drug sensitivity.
This article is a status report on the work being done by
my colleagues and myself toward meeting such challenges. It
begins by describing a scenario that offers a tantalizing
glimpse of the power of mobile information access. The major
obstacles on the path toward this vision are then examined.
The rest of the article is a summary of research on overcom-
ing these obstacles in the context of the Coda and Odyssey
systems.
A Vision of Tomorrow
Imagine this hypothetical scenario of a business trip in the
year 2000:
You are sitting at your office desk, editing a report stored
in a shared file system. The machine you are using is a small
notebook computer, but it lets you use the larger and more
comfortable display and keyboard on your desk via a tabletop
infrared link. Soon it is time to leave for the airport.
When the limousine arrives, you pick up your notebook
and leave. On the ride to the airport you continue your work.
Your notebook recognizes that it is no longer on a local area
network (LAN), but continues communication with the
servers via a cellular modem. You finish your editing, save the
file, and send mail to your coauthor letting him know that he
can now review your edits. You then begin working on the
slides for your talk in Paris. Upon arrival at the airport, you
board your transatlantic flight and continue working.
Although each seat is provided with an outlet for air-to-
ground telephone service, your notebook inquires and discov-
ers that telephone charges are very high. It therefore wisely
decides to let you operate disconnected and to defer all com-
munication until you have landed.
When you arrive in your Paris hotel room, your notebook
discovers that the hotel’s late-night telephone charges are low,
and that there is a high-definition television (HDTV) set in
your room. It therefore propagates the changes you have
made so far, fetches new versions of some of the files you had
cached, picks up your mail, and uses the HDTV set as your
display. You work late into the night, putting the finishing
touches on your slides. The next morning, you present your talk.
Your notebook senses the presence of a large wall-sized dis-
play in the conference room, and shows your slides on it.
Since your talk is about a new piece of user-interface soft-
ware, you are able to give a live demo of it using the notebook.
Once your business is complete, you decide to play tourist
for a day before returning home. The concierge at your hotel
subscribes you to an excellent guided walking tour, and rents
you a heads-up display and headphones. Setting out with your
notebook in your backpack, you pick a route from the map
displayed. As you walk, you indicate items of interest on the
map. A short video describing the unique historical and archi-
tectural features of the site is seen, and the accompanying
audio commentary is heard. As you pass through a major
shopping district, advertisements of sales (translated by your
notebook into English) pop up on your display.
One of these interests you, and you walk into the store and
purchase a gift. The store clerk obtains your travel itinerary
IEEE Personal Communications • February 199626 1070-9916/96/$05.00 © 1996 IEEE
T
This research was supported by the Air Force Materiel Command (AFMC)
and ARPA under contract number F196828-93-C-0193. Additional sup-
port was provided by the IBM Corp., Digital Equipment Corp., Intel Corp.,
Xerox Corp., and AT&T Corp. The views and conclusions contained here
are those of the authors and should not be interpreted as necessarily repre-
senting the official policies or endorsements, either express or implied, of
AFMC, ARPA, IBM, DEC, Intel, Xerox, AT&T, CMU, or the U.S. Gov-
ernment.
Mobile Information Access
Accessing information on demand at any location
Mahadev Satyanarayanan