00100	PROBLEMS OF NATURAL LANGUAGE UNDERSTANDING IN TELETYPED INTERVIEW DIALOGUES.
00150	
00200	
00300	     By `natural language` I shall mean everyday American English
00400	such as is used by readers of this book in ordinary conversations.
00500	It is still difficult to be explicit about the processes which
00600	enable hummans to interpret and respond to natural language.
00700	Philosophers, linguists and psychologists have speculated about
00800	and investigated natural language with various purposes and few
00900	useful results.  Now attempts are being made in artificial intelligence to write        
01000	algorithims which `understand' what is being expressed in natural
01100	language utterances.
01200	     During the 1960's when machine processing of natural language
01300	was dominated by syntactic considerations, it became clear that
01400	this approach was insufficient.  The current view is that to unDerstand
01600	what utterances say, knowledGe about linguistic syntax and semantics
01700	must be combined with knowledge about an underlying conceptual
01800	structure containing a world-model and an ability to draw inferences.
01900	How to achieve this combination efficiently represents a huge task for
02000	both theory and implementation.
02100	     Since the behavior  being simulated by  our paranoid model is the
02200	linguistic-conceptual behavior of paranoid patients in a psychiatric
02300	interview, the model must have some  ability to process and respond to
02400	natural language input in a manner indicating the underlying pathological
02500	
02600	to develop a method for understanding everyday Englisg sufficient
02700	for the model to behave conversationally in a paranoid way in a
02800	circumscribed situation.  What is said in this situation is far
02900	icher than what is said in conversations with a block-stacking
02950	i2900
03000	robot but its requirements for constructing an interpretation
03100	of an input are not as complex as trying to understand anything
03200	said in English BY anybody in any dialogue situation.
03300	WE TOOK A PRAGMATIC APPROACH WHICH CONSIDERED "UNDERSTANDING"
03400	TO REPRESENT "GETTING THE MESSAGE" OF  AN UTTERANCE BY
03500	GLEANING SOME {NOT ALL} OF THE RELATIONS BETWEEN THEM.
03600	THIS STRAIGHTFORWARD APPROACH TO A COMPLEX PROBLEM HAS ITS
03700	DRAWBACKS, AS WILL BE SHOWN, BUT WE WERE STRIVING FOR A
03800	SUFFICIENCY TO DEMONSTRATE PARANOIA RATHER THAN COMPLETE
03900	COMPREHENSION OF ENGLISH.
04000	     LINGUISTIC APPROACHES  CITE TRADTIONAL PROBLEMS WITH
04100	AMBIGUITY, AS ILLUSTRATED IN THE FOLLOWING EXAMPLE FROM
04200	WILKS {  }.  SUPPOSE I WALKED UP TO YOU, A STRANGER, ON
04300	THE STREET ON SUNDAY MORNING AND SAID
04400	     {1} `HE FELL WHILE GETTING TO THE BALL'.
04500	ADMITTEDLY THIS IS A STRANGE SCENE AND IN THIS SITUATION
04600	YOU WOULD THINK ME TO BE CRAZY, HUNGOVER AND MAYBE STILL
04700	DRUNK.  BUT THE EXAMPLE IS NO MORE WEIRD THAN THE ISOLATED
04800	EXAMPLES DISCUSSED IN THE LINGUISTICS LITERATURE.  SUPPOSE
04900	FURTHER THAT IN YOUR PERSONAL `DICTIONARY' THE WORD  `BALL'
05000	HAS AT LEAST TWO SENSES, {A} A SPHERICAL PHYSICAL OBJECT
05100	USED IN A GAME, AND {B} A FORMAL DANCE.  {IT PROBABLY HAS
05200	ALSO A THIRD SENSE AS A VERB BUT WE WILL IGNORE THIS MORE 
05300	OR LESS RECENT EXAMPLE OF SEMANTIC SHIFT}.  HAVING NO
05400	FURTHER INFORMATION IN THIS SITUATION AND ATTEMPTING TO
05500	CONSTRUCT AN INTERPRETATION OF MY UTTERANCE, YOU WOULD BE
05600	PUZZLED AS TO WHETHER I WAS REFERRING TO A BALL GAME OR A
05700	DANCE.  IF WE THEN CONTINUED ON OUR RESPECTIVE WAYS, SAYING
05800	NOTHING ELSE, YOUR PUZZLEMENT WOULD CONTINUE AND EVEN INCREASE
05900	--I DON'T KNOW WHAT HE WAS REFERRING TO NOR WHY HE EVEN SAID
06000	THAT TO ME.
06100	
06200	     THE AMBIGUITY ARISES BECAUSE OF THE TWO WORD SENSES FOR
06300	BALL EACH OF WHICH WOULD GIVE THE UTTERANCE A MEANINGFUL
06400	INTERPRETATION.  BUT THE EXAMPLE IS EXTREMELY FORCED AND
06500	ARTIFICIAL.  SUCH ISOLATED UTTERANCES CANNOT BE DISAMBIGUATED
06600	{UNIQUEATED IS A BETTER TERM} BUT THIS IS NO HANDICAP FOR
06700	ORDINARY HUMAN CONVERSATIONS IN WHICH AMBIGUITIES HARDLY ARISE
06800	AT ALL.  BBESIDES THE UTTERANCE ITSELF, EXTRA INFORMATION IS
06900	USUALLY AVAILABLE IN THE FORM OF CONTEXTUAL AND SITUATIONAL
07000	KNOWLEDGE.  EVEN BETTER, ONE CAN ALWAYS ASK.  IF I HAD SAID
07100	ONLY UTTERANCE {1} TO YOU, YOU COULD SIMPLY ASK:
07200	
07300	               {2} `WHAT DO YOU MEAN?'
07400	
07500	AND MY REPLY WOULD INDICATE SOMETHING ABOUT A GAME OR A
07600	DANCE OR WHO 'HE' WAS.
07700	    UTTERANCES OCCUR IN CONVERSATIONS WHICH TAKE PLACE IN
07800	SOCIOPSYCHOLOGICAL SITUATIONS.  THE COMMUNICANTS HAVE ROLES
07900	AND INTENTIONS TOWARDS ONE ANOTHER.  IF THE SITUATION IS THAT
08000	OF A MEDICAL OR PSYCHIATRIC INTERVIEW BETWEEN DOCTOR AND
08100	PATIENT AND THE DOCTOR ASKS:
08200	       {3}  "HOW MUCH DO YOU DRINK?"
08300	WE KNOW FROM THE NATURE OF THE SITUATION THAT DRINK MEANS
08400	`DRINK ALCOHOL' AND DOES NOT REFER TO A TOTAL FLUID INTAKE.
08500	     DIALOGUES REPRESENT CONNECTED DISCOURSE IN WHICH ALL
08600	THE UTTERANCES, EXCEPT PERHAPS FOR OPENING GREETINGS, ARE
08700	CONNECTABLE TO PREVIOUS UTTERANCES.  CONTEXTS AND SUB
08800	CONTEXTS, TOPICS AND SUBTOPICS SURROUND ANY GIVEN UTTERANCE
08900	AND ACTIVATE RELEVANT WORD SENSES SUCH THAT ALTERNATIVE
09000	SENSES DO NOT ARISE IN THE COMPREHENSION PROCESS.  IN
09100	SPOKEN DIALOGUES INTONATIONS AND WORD EMPHASES ARE FURTHER
09200	MEANS FOR AVOIDING AMBIGUITIES.  BUT THE CONNECTED DISCOURSE
09300	OF DIALOGUES BRINGS PROBLEMS OF ITS OWN TO THE ALGORITHMIST
09400	WHOSE PROGRAM MUST KEEP TRACK OF WHAT IS GOING ON AND WHAT
09500	HAS BEEN SAID BEFORE.  FOREMOST IS THE PROBLEM OF IMAPHORIC
09600	REFERENCE.
09700	
09800	ANAPHORA
09900	
10000	     AN ANAPHORIC REFERENCE IS A WORD OR PHRASE WHICH REFERS
10100	BACKWARDS {USUALLY, I.E. THERE ARE SOME RARE FORWARD REFERENCES}
10200	TO SOMETHING IN A PREVIOUS UTTERANCE.  A COMMON EXAMPLE IN
10300	INTERVIEW DIALOGUES IS THAT OF PRONOUNS.
10400	       {4} PATIENT - MY FATHER WAS AN ALCOHOLIC.
10500	
10600	       {5} DOCTOR - WERE YOU VERY CLOSE TO HIM?
10700	
10800	WHERE THE TERM `HIM' IN {4} OBVIOUSLY REFERS TO `FATHER' IN
10900	{3}.  IT IS NOT TOO DIFFICULT A PROBLEM FOR A PROGRAM TO MAKE
11000	THE CORRECT ASSIGNMENTS IN PERSONAL PRONOUN ANAPHORA.  OF
11100	GREATER COMPLEXITY ARE UTTERANCES CONTAINING THE WORDS `IT'
11200	OR `THIS'.  FOR EXAMPLE, SUPPOSE THE INTERVIEW CONTINUED AFTER
11300	{5} AS FOLLOWS:
11400	
11500	       {6} PATIENT - YES I WAS, EVEN THOUGH HIS DRINKING
11600	           UPSET ME.
11700	
11800	       {7} DOCTOR - HOW DID IT UPSET YOU?
11900	
12000	HERE THE COMPREHENSION ALGORITHM MUST GRASP THAT THE `IT' OF
12100	{7} REFERS TO THE TOPIC OF THE FATHER'S DRINKING IN {6}.
12200	FURTHER, IF THE DIALOGUE CONTINUED:
12300	
12400	       {8} PATIENT - IF EMBARASSED ME WHEN MY FRIENDS SAW
12500	           HIM DRUNK.
12600	
12700	       {9} DOCTOR - DO YOU THINK HE SENSED THIS?