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This draft is inconsistent in that my ideas changed as I wrote it, and
I have not yet altered the earlier sections to agree with the later
sections.  I also have not yet given examples of the application of
the general concepts advocated to the story of Mr. Hug.

AN EXAMPLE FOR NATURAL LANGUAGE UNDERSTANDING AND THE AI PROBLEMS IT RAISES


	The following story from  the New York Times is  my candidate
for  a target  for a  natural  language understander.   The  story is
about a real world event  and therefore the intentions of the  author
are less  relevant for answering  questions than  in the case  of the
story about Tad.

	"A  61-year old furniture salesman was  pushed down the shaft
of a  freight elevator yesterday  in his  downtown Brooklyn store  by
two robbers  while a third attempted  to crush him  with the elevator
car because they were  dissatisfied with the  $1,200 they had  forced
him to give them.

	The buffer springs at  the bottom of the shaft  prevented the
car from  crushing the salesman,   John J. Hug,   after he was pushed
from the  first floor  to the  basement.   The car  stopped about  12
inches above him as he flattened himself at the bottom of the pit..

	Mr. Hug wa  pinned in the shaft for about  half an hour until
his  cries attracted  the attention  of a  porter.   The stor  at 340
Livingston Street is part of the Seaman's Quality Furniture chain.

	Mr. Hug was removed by members of the  Police Emergency Squad
and taken to Long Island  College Hospital.  He was badly shaken, but
after being treated  for scrapes  of his left  arm and  for a  spinal
injury was  released and  went home.   He lives  at 62-01 69th  Lane,
Maspeth, Queens.

	He has worked  for seven years at the store, on the corner of
Nevins Street, and this  was the fourth time he  had been held up  in
the store.  The last time was  about one year ago, when his right arm
was slashed by a knife-wielding robber."

	An  intelligent person  or program  should be able  to answer
the following questions based on the information in the story.

	1. Who was in the store when the events  began?  Probably Mr.
Hug alone. although the robbers  might have been waiting for him, but
if so, this would have probably been stated.

	2. Who was in the store during the attempt to kill Mr.   Hug?
Mr. Hug  and the  robbers.  If  anyone else  were in  the store,   he
probably  would have interacted  with the situation  in some relevant
way.

	3. Who had the money at the end?  The robbers.

	4. Is Mr. Hug  alive today?   Yes, unless something else  has
happened to him.

	5.   How did  Mr. Hug  get hurt?   Probably  when he  hit the
bottom of the shaft.

	6.   Where  is Mr.   Hug's  home?   (A question  whose answer
requires  a  literal  understanding  of  only  one  sentence  of  the
stories.)

	7. What  are the  names and addresses  of the robbers?   This
informations was unknown to the reporter, to Mr. Hug, to the  police,
and, in fact, to any good citizens.

	8. Was  Mr. Hug conscious  after the robbers  left?   Yes, he
cried out and his cries were heard.

	9.   What would have  happened if Mr.   Hug had not flattened
himself at the bottom of the pit?  What would have happened  if there
were no buffer springs? Mr. Hug would have been crushed?

	10. Did Mr. Hug want to be crushed?  No.

	11. Did the robbers tell Mr. Hug their names?

	12. Were the robbers good people?  No.

	13. Did Mr. Hug like the robbers, and did they like him?

	14.   Why did  the robbers  leave without  killing Mr.   Hug?
Perhaps,   they thought they had killed  him, and perhaps their anger
was appeased by the actions they had performed, and  perhaps they had
taken  all  the  time  they  dared, and  perhaps  something  specific
happened to frighten them away.

	15. What would  have happened  if Mr.  Hug had  tried to  run
away? Perhaps  he would have  succeeded, but  more likely they  would
have shot him since probably they had guns.

	16. What  can Mr. Hug do  to avoid this in  the future?  What
can Seaman's Quality Furniture do?  What can the police do?

	The above list of questions  is rather random.  I doubt  that
it  covers all  facets  of  understanding the  story.    It would  be
worthwhile  to try  to make up  a list  of questions  that does cover
substantially all aspects  of the story in  order to get as  complete
as possible  an intuitive idea  of what capabilities  are involved in
understanding such a story.

	Note that the  story is  about a real  event so  that such  a
question as  what does the  "J" in "John  J.  Hug"  stand for  has an
answer.   In the  story about  Tad,  the  question of what  was Tad's
middle name or what year  the story occurred in does not  necessarily
have and answer unless,  for  example, the Tad referred to was really
the son of Abraham Lincoln whose name was Tad.

	I  think that  artificial intelligence  is not very  close to
being able to understand such  stories in a genuine way.   Therefore,
I  would like to  sneak up  on it gradually  by dividing  the problem
into parts which  can be attacked  separately. Here are  some of  the
components:

	1. A formalism capable of expressing the assertions of the
sentences free from dependence on the grammar of the English language.
A good test for such a formalism would be to produce a program for
translating from the formalism into any of several natural languages.
More weakly, it should be as easy for a human to translate from the
formalism into a natural language as to translate from one known
natural language to another.  

	The grammar of such a language would be trivial and mathematical
in character.  There would be an "English" version of the formalism in
which English words were used as identifiers, but there would still have
to be a glossary that gives the precise meaning of the identifiers.
There would also be a German and a Japanese version.  The translation from
the English version to the German or Japanese version would be a simple
substitution for identifiers, and a German or Japanese who had learned
the grammar could then translate into his language with the aid of the
German or Japanese glossary.

	This idea has some resemblance to the idea of "deep structure",
but I have some doubts about whether that idea is well enough defined
to say definitely whether it meets the above criteria.

	2.   A data structure  for expressing  the facts (apart  from
expressing  the sentences).  In such a data structure,   it would be
definite which robber pushed  Mr. Hug first,   and what the  robbers
said even though it is not stated in the story.  Clearly some compromise
is necessary here, since the data structure need not be able to express
positions and velocities of molecules.

	The basis of this data structure might be various networks of
nodes described by sentences in the predicate calculus.  Some of the
sentences would assert that certain programs applied to the data structures
would answer certain questions.  When such sentences existed, reasoning
would include the operation of the programs.  In this way, we would expect
to avoid the extreme prolixity that arises when we attempt to do even simple
calculations by pure predicate calculus deduction.

	The test of success for the "data structure" would be that a human could
readily formally deduce the answers to the above questions using a proof checker.
Most of the proof-checker would be straightforward, but there is a major problem
concerned with when it is possible to "jump to a conclusion".


	3. I see each of the following problems as a difficult AI problem:

		a. A "parser" that takes English into the "syntax free language".

		b. An "understander" that constructs the "facts" from a text
in the "syntax free language".

		c. Expression of the "general information" about the world that could
allow getting the answers to the questions by formal reasoning from the "facts"
and the "general information".
The "general information" would also contain non-sentence data structures and
procedures, but the sentences would tell what goals can be achieved by running
the procedures.  In this way, we would get the best of the sentential and
procedural representations of knowledge.

		d. A "problem solver" that could answer the above questions
on the basis of the "facts".  We imagine the questions to be expressed in the
"fact" language and expect the answers in the "fact" language, i.e. we avoid
grammar problems in both understanding the questions and in expressing the
answers.