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  <Title>INPUT SENTENCE ANALYSIS I TOPIC/C-TYPE I I / / /// -/,,,/ EVALUATION RULES ENGLISH GENERATOR ENGLISH RESPONSE TOPIC SELECTION RULES TRANSITIO~ I W~OTHER TOPIC~ SELECTIONS F INTEREST MICS CONTROL-FLOW</Title>
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Abstract
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    <Paragraph position="0"> This paper analyzes principles of human conversation based on the conversational goals of the participants. Several conversational rules are proposed that seem crucial to the process of interpreting and generating conversations. These rules, as well as other aspects of the conversation process, are embodied in MICS, a computer program that generates one side of a conversation. The process model underlying MICS, and some illustrative output, are presented.</Paragraph>
    <Paragraph position="1"> I) Formulating rules about human conversations.</Paragraph>
    <Paragraph position="2"> This paper is an empirical approach to understanding the processes that underlie human conversations. Since the task of codifying all the knowledge required for modeling human discourse is monumental, we confine our approach to formulating rules about the conversational intent of utterances in the course of a dialog.</Paragraph>
    <Paragraph position="3"> This approach leads us to investigate the effects of shared assumptions and knowledge between the speakers, the social and interpersonal relations of the speakers, and the inferences that must be made by both speakers in a conversation. We take a different approach to analyzing conversations than other research efforts, such as those adopting the speech-acts paradigm (Mann et al \[1977\]) or investigating task-specific dialogs (Grosz \[1977\])o in the hope that our new perspective will shed some light on otherwise obscure or neglected aspects of human discourse.</Paragraph>
    <Paragraph position="4"> Consider the following conversation fragment between Bill and John, two college students sharing an apartment: I) JOHN: Hi, what's new, Bill? BILL: l'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="5"> We can analyze Bill's utterance in Conversation Fragment (I) in terms of its immediate meaning, that is, a representation of Bill's utterance in Conceptual Dependency or some other meaning representation. This, however, is a very incomplete analysis of what Bill said. Why did Bill say that he was visiting his folks? Bill could just as easily have said, &amp;quot;I'm going to brush my teeth tonight.&amp;quot; This utterance, however, doesn't answer John's question; brushing one&amp;quot;s teeth is not &amp;quot;something new&amp;quot;. Therefore, we could propose a rather simple conversational rule: RULE I : If a question is asked in the course of a conversation, the other participant should answer this question.</Paragraph>
    <Paragraph position="6"> Rule I, however, is a little too naive.</Paragraph>
    <Paragraph position="7"> Suppose Bill's answer was: &amp;quot;There are a few more microns of dust on the windowsill than the last time you asked me that question.&amp;quot; This is indeed &amp;quot;something new&amp;quot;, but we would think of Bill as a wise guy for answering the question literally rather than addressing what John &amp;quot;must have meant&amp;quot;. What did John really mean? John must have been looking for something out of the ordinary and of some intrinsic importance. Let us propose a new rule to incorporate this principle: RULE 2: In the formulation of an answer, the speaker should address the true significance of the question, not just its literal meaning.</Paragraph>
    <Paragraph position="8"> What is the true significance of a question? In Conversation Fragment (I), Bill might have answered: &amp;quot;The J-particle angular momentum of +3/2 was confirmed today.&amp;quot; John, a literature major who does not understand Physics, may not be inclined to continue the conversation. Therefore, Bill's answer is not what was called for, unless Bill intentionally wanted to end the conversation. This example suggests that Bill missed something in establishing the true significance of John's question. John did, indeed, explicitly ask to hear something new; implicitly he meant something important and out of the ordinary. The J-particle answer conforms to these requirements, but it is still an inappropriate response. Therefore, the true significance of John's answer must include John's conversational goal. Why did John ask &amp;quot;What's new&amp;quot;? The answer is, obviously, to start a conversation with Bill. Bill, being aware of this conversational goal, needs to choose an answer that attempts to initiate conversation.</Paragraph>
    <Paragraph position="9"> That is, Bill should choose a topic of conversation that John can talk about and that John may be interested in. Conversational Rule (3) summarizes this discussion: RULE 3: In introducing a new topic of conversation, the topic should be chosen so that both speakers have some knowledge and interest in its discussion.</Paragraph>
    <Paragraph position="10"> The process of understanding the conversational import of an utterance may be conceptually divided into two primary subprocesses: I) determine the conversational goal of the utterance, and 2) establish the real, often implicit, meaning of the utterance. Lehnert \[1977\] analyzes the process of establishing the real meaning of questions. Our analysis focuses on the conversational goals of the participants and the establishment of a shared knowledge base between the participants. It is this shared cultural, personal, and factual knowledge that the conversational participants leave implicit in each commtmication. To illustrate this fact, consider Conversational Fragment (2):  2) JOHN: Do you want to go out and try the bar at Monument Square? BILL: I'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="11"> Real significance of Bill's utterance: i) No, I do not want to go to the M~nument Square bar.</Paragraph>
    <Paragraph position="12"> ii) My reason for not wanting to go is that I made a previous commitment, and I cannot be in two places at once tonight.</Paragraph>
    <Paragraph position="13">  ill) The previous commitment is a visit to my folks.</Paragraph>
    <Paragraph position="14"> iv) I am telling you about the reason why I cannot go drinking with you rather than just saying &amp;quot;no&amp;quot; because I do not want you to get angry at me.</Paragraph>
    <Paragraph position="15"> v) I may also wish to shift the topic of conversation to a discussion about my fam il y.</Paragraph>
    <Paragraph position="16"> Bill knows that John will interpret his answer so as to conclude its real significance; otherwise Bill would have chosen to explicitly state the real significance. How does Bill know that John will understand him correctly? Clearly Bill and John must share some common sense knowledge such as:  a) A person cannot be in two places at once.</Paragraph>
    <Paragraph position="17"> b) Previous commitments should be honored.</Paragraph>
    <Paragraph position="18"> c) If X's invitation or suggestion is turned down by Y without apparent reason, then X is likely to get upset at Y.</Paragraph>
    <Paragraph position="19"> d) If a person introduces a new topic in a conversation, he may want to discuss the current topic further,  Both Bill and John are aware that they share a common cultural knowledge base. This knowledge is very crucial in determining what is said in the conversation. Bill must have considered (1) through (iv) before deciding that is was sufficient to say only (ill). How did Bill decide to say only (ill)? He must have concluded that John would infer (i) , (ii) and (iv) without difficulty. Thus, Bill knew about John's general knowledge because of their common cultural background and their personal relation. Bill used this knowledge to decide what to say in the c onv er satlon.</Paragraph>
    <Paragraph position="20"> In the course of a conversation, people make assumptions about each other's knowledge. It is sometimes easier to see what these conversational assumptions are when they turn out to be incorrect, as in the following example:  3) PETE: How are you going to vote on Proposition 13? MARY: On what? PETE: You know, the property tax limitation.</Paragraph>
    <Paragraph position="21"> MARY: Oh yeah. I'm not registered to vote.</Paragraph>
    <Paragraph position="22">  Which way were you trying to convince me to vote? PETE: I was hoping you would help me make up my mind.</Paragraph>
    <Paragraph position="23"> MARY: Actually, I don't give a damn about politics.</Paragraph>
    <Paragraph position="24"> At the beginning of the conversation Pete ass~ed that Mary knew what Proposition 13 was, that she was able to vote, that she would vote, and that she had already decided how to vote on Proposition 13. All of these assumptions turned out to be incorrect, and the course of the conversation turned towards clarifying the incorrect ass~ptions. This example is an instance of a more general rule of conversation: RULE 4: If a participant in a conversation discovers that his assumptions about the shared knowlege between the two speakers is incorrect, then he will steer the conversation to I) establish a common knowledge base on a specific topic, or  2) discover what their shared knowledge is in general, or 3) shift the conversational topic to some matter where a common knowledge base is more likely to exist, or 4) end the conversation.</Paragraph>
    <Paragraph position="25">  The assumptions discussed thus far have been of a factual nature, but assumptions are also made about the conversational intent of the participants and about their interest in the conversational topic. Mary inferred Pete&amp;quot; s conversational intent incorrectly: He was seeking advice, not trying to lobby for or against Proposition 13. Pete started the entire conversation on the wrong topic by assuming that Mary was interested in politics or taxes. A conversation about a topic that one of the participants finds uninteresting will usually digress to other topics or fizzle out as the uninterested party volunteers no new information, finds an excuse to do something else, or states outright that the conversation is boring (as was the case in our example).</Paragraph>
    <Paragraph position="26"> Erroneous assumptions about conversational intent lead to misunderstandings because each speaker will address the perceived intent of the other speaker's utterance. It is, therefore, imperative to correctly infer the other speaker's conversational intentions in order for the conversation to proceed naturally. The type misunderstanding that often results from incorrectly perceived conversational intentions is, on occasion, exploited in creating certain types of jokes, as in example 4: 4) SON: Dad, I robbed the liquor store yesterday. DAD: How could you ever do such a thing, son? SON: Well, I got me this gun, and I pointed it at the cashier...</Paragraph>
    <Paragraph position="27"> To illustrate the importance of the implicit conversational goals and shared knowledge between the participants in a conversation, we present a few more dialog framents between Bill and John, the two college students sharing an apartment. In each example, as in conversations (I) and (2), Bill utters the same response, but its meaning is significantly different, depending on the context of the conversation.</Paragraph>
    <Paragraph position="28"> 5) JOHN: Are you broke again? You are going to have to come up with your share of the rent this month.</Paragraph>
    <Paragraph position="29"> BILL: I'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="30">  (i) Yes, l'm broke again.</Paragraph>
    <Paragraph position="31"> (il) Yes, I'll try to contribute my share of the rent.</Paragraph>
    <Paragraph position="32"> (iii) My parents might give me some money if I ask them.</Paragraph>
    <Paragraph position="33"> (iv) If I visit them and ask them in person I have a better chance of getting some money.</Paragraph>
    <Paragraph position="34"> (v) I'll visit them tonight and then I'll ask  them for money.</Paragraph>
    <Paragraph position="35"> When we read Conversation Fragment (5), we infer that Bill may be going to ask his parents for money. How do we do this? We do not share knowledge with Bill to the effect that his parents have money or that Bill is willing to ask them for money. The answer is based on a conversational rule: RULE 5: The utterances in a conversation should be connected by continuity of topic, common conversational goals, and each participant addressing the intent of the utterances of the other participant.</Paragraph>
    <Paragraph position="36"> Since the reader assumes that Rule (5) is true for Conversation Fragment (5), he concludes that there must be a connection between Bill needing money and the visit to his parents. The reader then infers the most likely connection: Bill will ask his parents for money. John must also make this inference based on Rule (5), unless he knows that Bill regularly visits his parents to ask for money. The significant point illustrated in example 5 is that the conversation focused the inference mechanism to find a connection between the respective utterances. Therefore, conversational principles can play an important role in focusing human reasoning processes. The principle of focusing inference processes on significant or interesting aspects of conversational utterances and events is developed into a theory of human subjective understanding in Carbonell \[1978\].</Paragraph>
    <Paragraph position="37"> Let us continue with the conversational fragments between Bill and John:  6) JOHN: How come you never see your family? BILL: I'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="38"> Meaning of Bill's utterance: (i) I do visit my family.</Paragraph>
    <Paragraph position="39"> (ii) Supporting evidence: I'm going to visit them tonight.</Paragraph>
    <Paragraph position="40"> (iii) Therefore, what you just said is not true. 7) JOHN: Can I borrow your car? I got this heavy date tonight.</Paragraph>
    <Paragraph position="41"> BILL: I'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="42"> Meaning of Bill's utterance: Alternative I.</Paragraph>
    <Paragraph position="43"> (i) No, you cannot borrow my car tonight.</Paragraph>
    <Paragraph position="44"> (il) I am going to visit my folks tonight.</Paragraph>
    <Paragraph position="45"> (iii) I need to drive there.</Paragraph>
    <Paragraph position="46"> (iv} The car cannot be fn two places at once. Alternative II, (i) Yes, you can borrow my car tonight.</Paragraph>
    <Paragraph position="47"> (ii) I am going to be at my folk's place, where I don't need to use it.</Paragraph>
    <Paragraph position="48"> 8) JOHN: Can I have the apartment to myself? I got this heavy date tonight.</Paragraph>
    <Paragraph position="49"> BILL: I'm going to visit my folks tonight.</Paragraph>
    <Paragraph position="50"> Meaning of Bill's utterance: (i) Yes, you can have the apartment.</Paragraph>
    <Paragraph position="51"> (ii) What you want is for me to be elsewhere. (iii) I was planning on that any~my, since I  am visiting my folks tonight.</Paragraph>
    <Paragraph position="52"> Conversation fragments (6), (7) and (8) illustrate the degree to which the understanding o f cony er sat ional utterances i s expectation-driven. The expectations are generated from previous utterances according to rule 5; the toplc, intent, and conversational goals introduced earlier in the conversation will be addressed by later utterances. In each case the same utterance on Bill's part is understood differently, depending on the context established by John' s previous utterance. Utterances in a conversation do not usually have a meaning independent of the rest of the conversation; their meaning is part of the context of the entire conversation. Thus, it is easy to see why quoting only a short passage from a conversation (or a political speech) can give that passage has an entirely different meaning from what was originally intended.</Paragraph>
    <Paragraph position="53"> The shared knowledge between two speakers depends on many different factors. Two speakers share a large amount of basic knowledge by merely being members of the human race (e.g. the basic drives that motivate humans such as hunger, self-preservation, etc .). More knowledge is shared if the two speakers are members of the same culture. (Much of the cultural and more basic human knowledge necessary to understand natural language is discussed in Schank and Ableson \[1977\].) If the two participants hold the same type of job, are professional colleages, or have the same special interests, then they will share some rather specific knowledge. Two people with the same special interests (such as football or radio-astronomy) will usually steer the conversation to a discussion of their common interest s.</Paragraph>
    <Paragraph position="54"> RULE 6: The topic of a conversation may drift to a subject where the conversational participants share a great amount of knowledge. Another factor that determines the knowledge shared by the participants in a conversation is their interpersonal relation, i.e., how well they know each other. In conversational fragment (7), Bill's response can be interpreted in two different weys by the reader, but_ John will i~terpret his response unambiguously. John must know whethe~ Bill's response means tha~ Bill needs  the car or whether John is free to use it ; otherwise, Bill would have been more specific in his answer.</Paragraph>
    <Paragraph position="55"> Social relations and the perceived goals of conversational participants play an important role in interpreting the meaning of conversational utterances. Let us first consider the influence of the social relations between the two participants :  9) ARMY GENERAL: I want a juicy hamburger.</Paragraph>
    <Paragraph position="56"> STAFF AIDE: Right away, sirl i0) 7-YEAR-OLD: I want a juicy hamburger.</Paragraph>
    <Paragraph position="57"> MOTHER: Maybe next wsek. We are having chicken today.</Paragraph>
    <Paragraph position="58"> II) PRISON INMATE I: I want a juicy hamburger.</Paragraph>
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