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<Paper uid="J87-1002">
  <Title>MODUS BREVIS FORMS (MODUS PONENS): Given Premises Conclusion Normal P ~ Q, P Q Missing Minor P--,- Q Q</Title>
  <Section position="12" start_page="4" end_page="4" type="relat">
    <SectionTitle>
5 RELATED WORK
5.1 ARGUMENT UNDERSTANDING
</SectionTitle>
    <Paragraph position="0"> Other researchers in natural language have studied arguments, in particular. However, the focus of the research in each case has been different. Birnbaum and the group at Yale (Birnbaum et al. 1980, McGuire et al. 1981) study two-way communication, developing an argument graph to display the points raised by both conversants.</Paragraph>
    <Paragraph position="1"> This graph is then used to determine the best moves on the part of an adversary, to challenge the position of the other conversant. Thus, the question of what responses to generate is investigated. On the other hand, there is little insight into how a hearer can detect the points being raised by the speaker, to construct this argument graph.</Paragraph>
    <Paragraph position="2"> Our focus has thus been on this preliminary problem to argument understanding.</Paragraph>
    <Paragraph position="3"> Archbold (Archbold 1976, Archbold and Hobbs 1980) is most concerned with evaluative arguments, those with strong underlying ideologies. For example, Lenin's speeches are appropriate sample input. Thus, the difficult question of recognizing differing opinions is a focus to Archbold's investigations. In addition, he studies text rather than discourse, allowing for a deeper review (re-reading) of the input in order to derive an analysis.</Paragraph>
    <Paragraph position="4"> Weiner (1979) describes a representation for arguments that is also a tree structure, with a variety of links possible. His main concern is to characterize types of argument structures, for use in the generation of explanations. There is thus little attention on the problems encountered in deriving argument structures during analysis. null Weiner's (1979) model for the structure of explanation bears some resemblance to the representation described for arguments here. Weiner claims that natural explanation can be regarded as a series of transformations of an underlying tree structure that represents the abstract form of the argument being developed. The ways in which support can be supplied are listed more extensively, including examples, alternatives, etc. How the tree can be built up relies on tracking a node that is &amp;quot;in focus&amp;quot;. The fact that determining the relations between statements may make use of clue words is mentioned briefly as well. Basically, some of the features we advocate appear in this research. But we are trying to provide more insight into operational questions such as: * How do you determine the (best) relation between propositions? * How is the focus set? and * When are clue words likely to occur? By contrast, Weiner concentrates on how to generate explanations using his precisely specified characterization. null Reichman (1981) is concerned with a larger problem of producing a model of discourse (not just arguments), but her approach should handle arguments as well. The core of the model is an ATN grammar for parsing and generation, coupled with a representation of &amp;quot;context spaces&amp;quot; containing conversational moves. The conversational moves provide a classification of larger components of discourse (not just single propositions). For example, there is an extensive study of a &amp;quot;challenge&amp;quot; operation. Since Reichman's aims are broader than ours, the lower level issues we address of verifying evidence and studying the necessity for clue words are not considered for the model. Moreover, there is an intentional lack of concern with pragmatic processing, another crucial feature our model. Instead, Reichman presents a model for the analysis of a variety of two-person interactions. null In sum, our efforts in argument understanding are worthwhile because we focus on the necessary first step in argument analysis - determining the intended structure, or &amp;quot;what the argument is about&amp;quot;. We study the possible structural relations between propositions, and investigate the difficult issue of verifying evidence relationships. The importance of pragmatic analysis to recognize whole classes of arguments that involve differing beliefs is stressed in our work. And finally, the use and interpretation of clue words is addressed. It is worth Computational Linguistics, Volume 13, Numbers 1-2, January-June 1987 21 Robin Cohen Analyzing the Structure of Argumentative Discourse noting that the differences in our existing studies can possibly be exploited by pooling efforts and suggesting a powerful general model for argument analysis.</Paragraph>
  </Section>
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