Modeling Negotiation Subdialogues

MODELING NEGOTIATION SUBDIALOGUES 1 Lynn Lambert and Sandra Carberry Department of Computer and Information Sciences University of Delaware Newark, Delaware 19716, USA email : lambert~cis, udel. edu, carberry@cis, udel. edu Abstract This paper presents a plan-based model that han- dles negotiation subdialogues by inferring both the communicative actions that people pursue when speaking and the beliefs underlying these actions. We contend that recognizing the complex dis- course actions pursued in negotiation subdialogues (e.g., expressing doubt) requires both a multi- strength belief model and a process model that combines different knowledge sources in a unified framework. We show how our model identifies the structure of negotiation subdialogues, including recognizing expressions of doubt, implicit accep- tance of communicated propositions, and negotia- tion subdialogues embedded within other negotia- tion subdialogues. 1 Introduction Since negotiation is an integral part of multi-agent activity, a robust natural language un- derstanding system must be able to handle subdi- alogues in which participants negotiate what has been claimed in order to try to come to some agreement about those claims. To handle such dialogues, the system must be able to recognize when a dialogue participant has initiated a nego- tiation subdialogue and why the participant began the negotiation (i.e., what beliefs led the partici- pant to start the negotiation). This paper presents a plan-based model of task-oriented interactions that assimilates negotiation subdialogues by in- ferring both the communicative actions that peo- ple pursue when speaking and the beliefs under- lying these actions. We will argue that recogniz- ing the complex discourse actions pursued in ne- gotiation subdialogues (e.g., expressing doubt) re- quires both a multi-strength belief model and a processing strategy that combines different knowl- edge sources in a unified framework, and we will show how our model incorporates these and rec- ognizes the structure of negotiation subdialogues. 2 Previous Work Several researchers have built argument un- derstanding systems, but none of these has ad- dressed participants coming to an agreement or mutual belief about a particular situation, ei- ther because the arguments were only monologues 1 This work is being supported by the National Science Foundation under Grant No. IRI-9122026. The Govern- ment has certain rights in this material. (Cohen, 1987; Cohen and Young, 1991), or be- cause they assumed that dialogue participants do not change their minds (Flowers, McGuire and Birnbaum, 1982; Quilici, 1991). Others have ex- amined more cooperative dialogues. Clark and Schaefer (1989) contend that utterances must be grounded, or understood, by both parties, but they do not address conflicts in belief, only lack of un- derstanding. Walker (1991) has shown that evi- dence is often provided to ensure both understand- ing and believing an utterance, but she does not address recognizing lack of belief or lack of under- standing. Reichman (1981) outlines a model for informal debate, but does not provide a detailed computational mechanism for recognizing the role of each utterance in a debate. In previous work (Lambert and Carberry, 1991), we described a tripartite plan-based model of dialogue that recognizes and …

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