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C00002 00002		An  intelligent  computer  program   that   understands   the
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	An  intelligent  computer  program   that   understands   the
physical, psychological and social world well enough to intelligently
solve problems in it must be able to represent facts about the  world
in  general,  particular  situations, the purposes of others, and the
laws that determine the effects of actions.  In our opinion, this  is
one  of  the  main  problems  that has to be solved before artificial
intelligence is a reality.  John McCarthy has  been  working  on  the
representation  problem  for a number of years and will continue this
work.  Present and proposed efforts are based on the use of sentences
in  first  order  logic  and  set  theory  as  the  primary  means of
representing facts.  The meaning of  other  data  structures  and  of
programs  is described by such sentences.  The work is facilitated by
the existence of a reasonably convenient proof checking  program  for
this  logic and substantial bases of axioms in machinable form.  From
various points of view, Luckham, Feldman,  Weyhrauch  and  Newey  are
also concerned with the representation problem.

	To make this concrete, consider the problem of travelling
to a foreign city.  The following kinds of information have to be
represented.  (1) The general facts about airplanes, cars, and
walking and the effects of actions using them. (2) The location
and format of information of various kinds, e.g. airline schedules
in the airline guide and in the knowledge of travel agents (3) The
facts about what other people must do or refrain from doing in order
to travel, e.g. the ticket agent must give you a ticket which he
will do in exchange for money in order that the gate agent will
refrain from preventing you from getting on the plane.  (4) There
is also information about what information does not have to be
known in advance because it will be available when needed such as
what gate a plane at the second stage of the journey will leave
from and how to get to the gate.  The test of whether this
information has been successfully put into the computer can be
made by having a proof checker check a proof that a given strategy
for making a journey will work barring accidents, strikes, and
other acts of God or government.  In our opinion, understanding
the kinds of information required to achieve a class of goals is
necessary before it is reasonable to have question answerers or
natural-language-understanders solve such problems or converse
in natural language about them.

	In the next contract period the Stanford Artificial 
Intelligence Laboratory proposes to increase our ability to
represent information in computers.  In particular, we plan to use
the above-mentioned travel problem as the basis for our work.