A Procedural Model of Language Understanding Terry Winograd in Schank and Colby, eds., Computer Models of Thought and Language, Freeman, 1973 발표자 : 소길자

Index Introduction The presentation of meaning Semantic analysis The role of syntax Limitations of the Approach

Introduction Much of the research on language is based on an attempt to separate it into distinct componets –Ordering of syntactic constitunets –Define semantic relations –Model the cognitive structures

Introduction 의미를 다루는 시스템들의 한계 – 배탁적으로 하나의 문장만 이해한다. 인간의 의미해석 – 전후 문맥을 이해한다. –We make use of What has gone on to help interpret what is coming

Introduction This Paper describes –an attempt to explore the interconnection between the different types of Knowledge required for language understanding –Ex) –Syntactic knowledge “ Arthur wants to see him ” : “ him ” must refer to someone other than Arthur –Semantic knowledge –Heuristic Knowledge –Knowledge of the world “ Sam and Bill wanted to take the girs to the movies, but they didn ’ t have any money ”

Introduction It is folly to think of giving the program all the knowledge our program –mini-world –We can give the computer a deep kind of knowledge –The world of toy robot with a simple arm

Introduction Three domain –Syntactic parser –Collection of semantic routine –Cognitive deductive system Exploring the consequences of facts Making plans to carry out commands Finding the answers to questions –The main emphasis The interaction of the three domains

Introduction One of the most useful organizing principles –Representation of much of the knowledge as procedures Many other theories of language –State their rules in a form modelled on the equations of mathematics or rules of symbolic logic To preserve the simplicity –Putting the knowledge in the form of program

Sample Dialogue Q: Pick up a big red block A: OK

The Representation of Meaning A detailed world model –Describing the current state of blocks –Describing Its knowledge of procedures for changing that state and making deductions about it

Database of simple facts Relationships between objects –Is, Support 등 Concepts –Block, Blue 등 Proper name of individual objects and events –B1, Table2, Event27 등

Representations of meaning The symbols used in these expressions represent the concepts(conceptual categories) Concept –corresponds vaguely to a single meaning of a word –The connection is more complex –Ex) ‘ truth ’, ’ virtue ’, ‘ democracy ’

Representations of meaning System ’ s knowledge which involves the interconnections between the concepts –In our model, these are in the form of procedures –Ex ) CLEARTOP

GRASP

This subgoal structure provides the basis for asking “ why ” questions -Q : why did you put B2 on the table? -A : To get rid of it -Q : why did you get rid of it? -A : To grasp B1

“ A red cube which supports a pyramid ”

Semantic Analysis 영어 입력문장이 들어오면 이를 해석해야 내 부적으로 프로그램을 생성할 수 있다. Definition for “ CUBE ”, ” CONTAIN ”

Semantic Analysis Usage –Q: can the table pick up blocks –A:No Table :INANIMATE Pick up : ANIMATE Rules are calls to program(OBJECT and RELATION) which do the appropriate checks and build semantic structure Flexibility is done by having the definition of every word be a program

Semantic Analysis Ex) –“ a big red block and a little one ” –“ one ” must trigger a program which looks into the previous discourse It tracks of when in the dialogue something is mentioned

The Role of Syntax In process of semantic interpretation, part of the relevant input was the syntactic structure The program contains a parser and grammar “ the three big red dogs ate a raw steak ”

The Role of Syntax For each unit, there is a syntactic program (written is PROGRAMMAR language). It will call on other such syntactic programs (and possibly on itself recursively)

The Role of Syntax Our grammar takes advantage of some of ideas of Systemic Grammar(Halliday,1971) –Features –Functions –Ex) “ the three big red dogs ” –Features : DETERMINED, INDEFINITE,PLURAL..etc –Functions : SUBJECT

Vertical Line : selection Horizontal Line : logical dependency MAJOR : independent sentence DECLARATIVE : she went IMPERATIVE : go INTERROGATIVE : did she go? SECONDARY : “ the ball which is on the table ”

The Role of Syntax Syntactic features are basic to description of semantic rules Formalism for describing syntactic process –Our grammar is written in a language which was designed for the purpose, PROGRAMMAR

Program Organization Parsing, semantic analysis, deduction go on concurrently throughout the understanding of a sentence “ Put the blue pyramid on the block in the box ” –Parser : “ the blue pyramid ” 를 Noun group 으로 구분 –Semantic analysis : “ the ” 의 대상이 되는 object 를 database 에서 검색

Program Organization There is a continuing interplay between the different sorts of analysis, with the results of one affecting the others

Limitations of the Approach The program does not attempt to handle hypothetical or counterfactual statement –Only accepts a limited range of declarative information It cannot talk about verbal acts

Limitations of the Approach Not dealing with all the implications of viewing language as a process of communication between two intelligent