A Structural Study Of Argumentation

In reality,we have often to reason about inconsistent and incomplete information in a non-monotonic way.While classical logic and traditional non-monotonic formalisms meet their own limitations on modeling this kind of reasoning,the argumentation theory provides us with a new way in this regard.Within this theory,a complete process of reasoning is divided into several conflicting arguments,and the justification of propositions relies on both the reasoning in argument and conflicts between arguments.Over the past 20 years,the theory of argumentation,influenced by Phan Minh Dung's(1995)minimalist model and extension-based argumentation semantics,has made great achievement in the respect of conflict calculation,but it does not give enough attention to the function of reasoning in argument.Consequently,it will not have a good effect on the construction of the extended-model in argumentation on the one hand,and it will also restrain the application prospect of argumentation theory on the other.The structural study of argumentation is realized through analyzing the internal elements within argumentation and fulfilling the depiction of conflicts.Therefore,such kind of analysis will be conducive to releasing some fundamental properties of argumentation that have not been touched in abstract research,shedding light on the application of argumentation theory,and foregrounding the basic role of logic in argumentation study.The corresponding model is thus named as structural argumentation system.Compared with the existing typical systems that feature efficient computation or abstract properties,Defeasible Logic Argumentation System(DLA)introduced in this dissertation concerns more about how to naturally characterize real-life reasoning.This dissertation consists of six chapters.Chapter 1 briefly reviews the history of argumentation study and its current situation,based on which it sorts out a vein of historical development of "mixed research on argumentation and logic-marginalization of argumentation in logic-reintroduction of argumentation-marginalization of logic in argumentation-reintroduction of logic".It then points out the structural argumentation which stands for a new trend of "reintroduction of logic",and finally offers the significance of the study as well as its overall organization.Chapter 2 delineates some existing formal argumentation models,like abstract argumentation framework and structural argumentation systems.By presenting each model,we investigate different elements(such as language choice,argumentation construction,definition of conflict,defeating evaluation)which should be taken into consideration within the system.This chapter also paves a way for the construction of the new system.Chapter 3 constructs a structural argumentation model,namely DLA.This model is composed of basic setting,computation mechanism,and system property.Basic setting defines the semantic and syntax of DLA,based on which it also defines argumentation structure,conflicts and defeats.Computation mechanism defines the evaluation process of the status of arguments under Dung's argumentation framework,and improves the computation efficiency by dint of a division-based method.System property explores the epistemological base of logic language in DLA,and examines the meta-properties of this system from a rational perspective.Chapter 4 interrogates the expressive capacity of DLA through case studies.For one thing,we use DLA to depict debate competition and legal argumentation and then indicate the merits and demerits of DLA.For another,we analyze the the Socratic elenchus-style argumentation,which has not been given enough priority in traditional studies,and formalize it in DLA.Chapter 5 provides a comparison between DLA and other popular structural argumentation systems,expecting to investigate the advantages and disadvantages of DLA in language expression,argument generation,priority relation,conflict calculation,and so on.Chapter 6 summarizes the research findings and viewpoints of the dissertation.In the end,it points out the orientation in future work.