Defeasible Reasoning and Argument-Based Systems in Medical Fields: An Informal Overview
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paper_title: A Logic of Argumentation for Reasoning under Uncertainty.

paper_content:

We present the syntax and proof theory of a logic of ar gumentation, LA. We also outline the development of a category theoretic semantics for LA. LA is the core of a proof theoretic model for reasoning under uncertainty. In this logic, propositions are labelled with a representation of the arguments which support their validity. Arguments may then be aggregated to collect more information about the potential validity of the propositions of interest. W e make the notion of aggregation primitive to the logic, and then define strength mappings from sets of ar guments to one of a number of possible dictionaries. This provides a uniform framework which incorporates a number of numerical and symbolic techniques for assigning subjective confidences to propositions on the basis of their supporting ar guments. These aggregation techniques are also described, with examples.
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paper_title: Towards a framework for rhetorical argumentation

paper_content:

This paper presents an approach towards the definition of a formal framework for rhetorical argumentation. Before describing the competence theory behind the framework, we introduce the notion of rhetorical argument, and describe the New Rhetoric, a well known theory in the philosophy of argumentation, upon which our work is based. 1 Motivation The study of argumentation has undergone periods of decadence alternate with periods of renaissance. Currently, we are witnessing one of the latter, as proved by research flowering in many issues and aspects, both in Philosophy and in Artificial Intelligence. The work presented in this paper is concerned in particular with rhetorical argumentation, which on the other hand has enjoyed consideration to a somewhat lesser extent. By rhetorical argument we want to denote arguments which are both heavily based on the audience’s perception of the world, and concerned more with evaluative judgments than with establishing the truth or otherwise of a proposition, like those in the following dialogue 1 :
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paper_title: On The Acceptability Of Arguments And Its Fundamental Role In Nonmonotonic Reasoning, Logic Programming And N-Persons Games

paper_content:

The purpose of this paper is to study the fundamental mechanism, humans use in argumentation, and to explore ways to implement this mechanism on computers. We do so by first developing a theory for argumentation whose central notion is the acceptability of arguments. Then we argue for the “correctness” or “appropriateness” of our theory with two strong arguments. The first one shows that most of the major approaches to nonmonotonic reasoning in AI and logic programming are special forms of our theory of argumentation. The second argument illustrates how our theory can be used to investigate the logical structure of many practical problems. This argument is based on a result showing that our theory captures naturally the solutions of the theory of n-person games and of the well-known stable marriage problem. By showing that argumentation can be viewed as a special form of logic programming with negation as failure, we introduce a general logic-programming-based method for generating meta-interpreters for argumentation systems, a method very much similar to the compiler-compiler idea in conventional programming. Keyword: Argumentation; Nonmonotonic reasoning; Logic programming; n-person games; The stable marriage problem
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paper_title: Combining statistics and arguments to compute trust

paper_content:

We propose a method for constructing Dempster-Shafer belief functions modeling the trust of a given agent (the evaluator) in another (the target) by combining statistical information concerning the past behaviour of the target and arguments concerning the target's expected behaviour. These arguments are built from current and past contracts between evaluator and target. We prove that our method extends a standard computational method for trust that relies upon statistical information only. We observe experimentally that the two methods have identical predictive performance when the evaluator is highly "cautious", but our method gives a significant increase when the evaluator is not or is only moderately "cautious". Finally, we observe experimentally that target agents are more motivated to honour contracts when evaluated using our model of trust than when trust is computed on a purely statistical basis.
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paper_title: Argumentative agents

paper_content:

Argumentation, initially studied in philosophy and law, has been researched extensively in computing in the last decade, especially for inference, decision making and decision support, dialogue, and negotiation. This paper focuses on the use of argumentation to support intelligent agents in multi-agent systems, in general and in the ARGUGRID project1 and Agreement Technology action2. In particular, the paper reviews how argumentation can help agents take decisions, either in isolation (by evaluating pros and cons of conflicting decisions) or in an open and dynamic environment (by assessing the validity of information they become aware of). It also illustrates how argumentation can support negotiation and conflict resolution amongst agents (by allowing them to exchange information and fill in gaps in their incomplete beliefs). Finally, the paper discusses how arguments can improve the assessment of the trustworthiness of agents in contract-regulated interactions (by supporting predictions on these agents' future behaviours).
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paper_title: Argumentation and Persuasion in the Cognitive Coherence Theory

paper_content:

This paper presents a coherentist approach to argumentation that extends previous proposals on cognitive coherence based agent communication pragmatics (inspired from social psychology) and propose (1) an alternative view on argumentation that is (2) part of a more general model of communication. In this approach, the cognitive aspects associated to both the production, the evaluation and the integration of arguments are driven by calculus on a formal characterization of cognitive coherence.
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paper_title: Argumentation in artificial intelligence

paper_content:

Over the last ten years, argumentation has come to be increasingly central as a core study within Artificial Intelligence (AI). The articles forming this volume reflect a variety of important trends, developments, and applications covering a range of current topics relating to the theory and applications of argumentation. Our aims in this introduction are, firstly, to place these contributions in the context of the historical foundations of argumentation in AI and, subsequently, to discuss a number of themes that have emerged in recent years resulting in a significant broadening of the areas in which argumentation based methods are used. We begin by presenting a brief overview of the issues of interest within the classical study of argumentation: in particular, its relationship-in terms of both similarities and important differences-to traditional concepts of logical reasoning and mathematical proof. We continue by outlining how a number of foundational contributions provided the basis for the formulation of argumentation models and their promotion in AI related settings and then consider a number of new themes that have emerged in recent years, many of which provide the principal topics of the research presented in this volume.
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paper_title: Justification And Defeat

paper_content:

This paper exhibits some problematic cases of defeasible or nonmonotonic reasoning that tend to be handled incorrectly by all of the theories of defeasible and nonmonotonic reasoning in the current literature. The paper focuses particularly on default logic, circumscription, and the author's own argument-based approach to defeasible reasoning. A proposal is made for how to deal with these problematic cases. The paper closes with a demonstration that the proposed solution is able to differentiate, in a congenial way, between cases having the structure of the lottery paradox and cases having the structure of the paradox of the preface. The algorithm proposed for computing justificational status has been implemented in the automated defeasible reasoner OSCAR.
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paper_title: An abstract framework for argumentation with structured arguments

paper_content:

An abstract framework for structured arguments is presented that instantiates Dung’s (1995) abstract argumentation frameworks. Arguments are defined as inference trees formed by applying two kinds of inference rules: strict and defeasible rules. This naturally leads to three ways of attacking an argument: attacking a premise, attacking a conclusion and attacking an inference. To resolve such attacks, preferences may be used, which leads to three corresponding kinds of defeat: undermining, rebutting and undercutting defeat. The nature of the inference rules, the structure of the logic al language on which they operate and the origin of the preferences are, apart from some basic assumptions, left unspecified. The resulting framework integrates work of Pollock, Vreeswijk and others on the structure of arguments and the nature of defeat, and extends it in several respects. Various rationality postulates are proven to be satisfied by the framework, and several existing approaches a re proven to be a special case of the framework, including assumption-based argumentation and DefLog. In 1995 Phan Minh Dung introduced an abstract formalism for argumentation-based inference (Dung 1995), which assumes as input nothing else but a set (of arguments) ordered by a binary relation (of attack). Although he thus fully abst racted from the structure of arguments and the nature of the attack relation, he was still able to develop an extremely interesting theory. His article was a breakthrough in three ways: it provided a general and intuitive semantics for the consequence notions of argumentation logics (and for nonmonotonic logics in general); it made a precise comparison possible between different systems (by translating them into his abstract format); and it made a general study of formal properties of systems possible, which are inherited by instantiations of his framework. In consequence, Dung’s work has given an enormous boost to re search in computational argumentation. Yet it has also been criticised for not speci fying the structure of arguments and the nature of the attack relation, which makes it less sui table for modelling specific argumentation problems. I believe that such criticism fails t o appreciate the nature of Dung’s formalism. It is best seen not as a formalism for directly rep resenting argumentation-based inference problems but as a tool for analysing particular argumentation systems and for developing a metatheory of such systems. As such it has been very successful: differences between particular systems can be characterised in terms of some simple notions, and formal results established for the framework are inherited by its instantiations. This was already illustrated by Dung (1995) with reconstructions of Pollock’s (1987) system, various logic-programming semantics and Reiter’s (1980) d efault logic in his formalism.
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paper_title: Reasoning about preferences in argumentation frameworks

paper_content:

The abstract nature of Dung's seminal theory of argumentation accounts for its widespread application as a general framework for various species of non-monotonic reasoning, and, more generally, reasoning in the presence of conflict. A Dung argumentation framework is instantiated by arguments and a binary conflict based attack relation, defined by some underlying logical theory. The justified arguments under different extensional semantics are then evaluated, and the claims of these arguments define the inferences of the underlying theory. To determine a unique set of justified arguments often requires a preference relation on arguments to determine the success of attacks between arguments. However, preference information is often itself defeasible, conflicting and so subject to argumentation. Hence, in this paper we extend Dung's theory to accommodate arguments that claim preferences between other arguments, thus incorporating meta-level argumentation based reasoning about preferences in the object level. We then define and study application of the full range of Dung's extensional semantics to the extended framework, and study special classes of the extended framework. The extended theory preserves the abstract nature of Dung's approach, thus aiming at a general framework for non-monotonic formalisms that accommodate defeasible reasoning about as well as with preference information. We illustrate by formalising argument based logic programming with defeasible priorities in the extended theory.
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paper_title: An abstract argumentation framework with varied-strength attacks

paper_content:

In classical abstract argumentation, arguments interact with each other through a single abstract notion of attack. However, several concrete forms of argument conflict are present in the literature, all of them of different nature and strength for a particular context. In this work we define an argumentation framework equipped with a set of abstract attack relations of varied strength. Using this framework, semantic notions dealing with the relative difference of strength are introduced. The focus is put on argument defense, and the study of admissible sets according to the quality of defenders.
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paper_title: Probabilistic Argumentation Frameworks: Basic Properties and Computation

paper_content:

In this paper we analyze probabilistic argumentation frameworks PAF, defined as an extension of Dung abstract framework in which each argument n is asserted with a probability p n and where an argumentation semantics is used to compute arguments’ status. We start by extending recent definitions of PAF removing the hypothesis of arguments independence, extending the computation to preferred semantics and defining the distribution of various probabilities induced over arguments acceptability status. We then prove some basic properties linking grounded and preferred PAF and we describe the first algorithm to compute the probability of acceptance of each argument. We end our work with an application of PAF to legal reasoning.
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paper_title: Fuzzy Argumentation Frameworks

paper_content:

We propose fuzzy argumentation frameworks as a conservative extension of traditional argumentation frameworks[6]. The fuzzy approach enriches the expressive power of the classical argumentation model by allowing to represent the relative strength of the attack relationships between arguments, as well as the degree to which arguments are accepted. Furthermore, we explore the relationship with fuzzy answer set programming, more in particular the correspondence between the stable extensions of a fuzzy argumentation framework and the fuzzy models of an associated program.
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paper_title: An abstract framework for argumentation with structured arguments

paper_content:

An abstract framework for structured arguments is presented that instantiates Dung’s (1995) abstract argumentation frameworks. Arguments are defined as inference trees formed by applying two kinds of inference rules: strict and defeasible rules. This naturally leads to three ways of attacking an argument: attacking a premise, attacking a conclusion and attacking an inference. To resolve such attacks, preferences may be used, which leads to three corresponding kinds of defeat: undermining, rebutting and undercutting defeat. The nature of the inference rules, the structure of the logic al language on which they operate and the origin of the preferences are, apart from some basic assumptions, left unspecified. The resulting framework integrates work of Pollock, Vreeswijk and others on the structure of arguments and the nature of defeat, and extends it in several respects. Various rationality postulates are proven to be satisfied by the framework, and several existing approaches a re proven to be a special case of the framework, including assumption-based argumentation and DefLog. In 1995 Phan Minh Dung introduced an abstract formalism for argumentation-based inference (Dung 1995), which assumes as input nothing else but a set (of arguments) ordered by a binary relation (of attack). Although he thus fully abst racted from the structure of arguments and the nature of the attack relation, he was still able to develop an extremely interesting theory. His article was a breakthrough in three ways: it provided a general and intuitive semantics for the consequence notions of argumentation logics (and for nonmonotonic logics in general); it made a precise comparison possible between different systems (by translating them into his abstract format); and it made a general study of formal properties of systems possible, which are inherited by instantiations of his framework. In consequence, Dung’s work has given an enormous boost to re search in computational argumentation. Yet it has also been criticised for not speci fying the structure of arguments and the nature of the attack relation, which makes it less sui table for modelling specific argumentation problems. I believe that such criticism fails t o appreciate the nature of Dung’s formalism. It is best seen not as a formalism for directly rep resenting argumentation-based inference problems but as a tool for analysing particular argumentation systems and for developing a metatheory of such systems. As such it has been very successful: differences between particular systems can be characterised in terms of some simple notions, and formal results established for the framework are inherited by its instantiations. This was already illustrated by Dung (1995) with reconstructions of Pollock’s (1987) system, various logic-programming semantics and Reiter’s (1980) d efault logic in his formalism.
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paper_title: Weighted argument systems: Basic definitions, algorithms, and complexity results

paper_content:

We introduce and investigate a natural extension of Dung's well-known model of argument systems in which attacks are associated with a weight, indicating the relative strength of the attack. A key concept in our framework is the notion of an inconsistency budget, which characterises how much inconsistency we are prepared to tolerate: given an inconsistency budget @b, we would be prepared to disregard attacks up to a total weight of @b. The key advantage of this approach is that it permits a much finer grained level of analysis of argument systems than unweighted systems, and gives useful solutions when conventional (unweighted) argument systems have none. We begin by reviewing Dung's abstract argument systems, and motivating weights on attacks (as opposed to the alternative possibility, which is to attach weights to arguments). We then present the framework of weighted argument systems. We investigate solutions for weighted argument systems and the complexity of computing such solutions, focussing in particular on weighted variations of grounded extensions. Finally, we relate our work to the most relevant examples of argumentation frameworks that incorporate strengths.
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paper_title: On The Acceptability Of Arguments And Its Fundamental Role In Nonmonotonic Reasoning, Logic Programming And N-Persons Games

paper_content:

The purpose of this paper is to study the fundamental mechanism, humans use in argumentation, and to explore ways to implement this mechanism on computers. We do so by first developing a theory for argumentation whose central notion is the acceptability of arguments. Then we argue for the “correctness” or “appropriateness” of our theory with two strong arguments. The first one shows that most of the major approaches to nonmonotonic reasoning in AI and logic programming are special forms of our theory of argumentation. The second argument illustrates how our theory can be used to investigate the logical structure of many practical problems. This argument is based on a result showing that our theory captures naturally the solutions of the theory of n-person games and of the well-known stable marriage problem. By showing that argumentation can be viewed as a special form of logic programming with negation as failure, we introduce a general logic-programming-based method for generating meta-interpreters for argumentation systems, a method very much similar to the compiler-compiler idea in conventional programming. Keyword: Argumentation; Nonmonotonic reasoning; Logic programming; n-person games; The stable marriage problem
---
paper_title: Justification And Defeat

paper_content:

This paper exhibits some problematic cases of defeasible or nonmonotonic reasoning that tend to be handled incorrectly by all of the theories of defeasible and nonmonotonic reasoning in the current literature. The paper focuses particularly on default logic, circumscription, and the author's own argument-based approach to defeasible reasoning. A proposal is made for how to deal with these problematic cases. The paper closes with a demonstration that the proposed solution is able to differentiate, in a congenial way, between cases having the structure of the lottery paradox and cases having the structure of the paradox of the preface. The algorithm proposed for computing justificational status has been implemented in the automated defeasible reasoner OSCAR.
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paper_title: A Labelling-Based Justification Status of Arguments

paper_content:

In this paper, we define a labelling-based justification status of the arguments in an argumentation framework. Our proposal allows for a more fine-grained notion of a justification status than the traditional extensions-based approaches. In particular, we are able to distinguish different levels at which an argument can be accepted or rejected. Our approach is fully compatible with traditional abstract argumentation in the sense that it works on standard argumentation frameworks and can be implemented using existing argumentation-based proof procedures.
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paper_title: On The Acceptability Of Arguments And Its Fundamental Role In Nonmonotonic Reasoning, Logic Programming And N-Persons Games

paper_content:

The purpose of this paper is to study the fundamental mechanism, humans use in argumentation, and to explore ways to implement this mechanism on computers. We do so by first developing a theory for argumentation whose central notion is the acceptability of arguments. Then we argue for the “correctness” or “appropriateness” of our theory with two strong arguments. The first one shows that most of the major approaches to nonmonotonic reasoning in AI and logic programming are special forms of our theory of argumentation. The second argument illustrates how our theory can be used to investigate the logical structure of many practical problems. This argument is based on a result showing that our theory captures naturally the solutions of the theory of n-person games and of the well-known stable marriage problem. By showing that argumentation can be viewed as a special form of logic programming with negation as failure, we introduce a general logic-programming-based method for generating meta-interpreters for argumentation systems, a method very much similar to the compiler-compiler idea in conventional programming. Keyword: Argumentation; Nonmonotonic reasoning; Logic programming; n-person games; The stable marriage problem
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paper_title: Mixed-Initiative Argumentation: Group Decision Support in Medicine

paper_content:

This paper identifies ways in which traditional approaches to argumentation can be modified to meet the needs of practical group decision support. Three specific modifications are proposed. Firstly, a framework for accrual-based argumentation is presented. Second, a framework for outcome-driven decision rationale management is proposed that permits a novel conception of mixed-initiative argumentation. The framework is evaluated in the context of group decision support in medicine.
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paper_title: Argumentation for Aggregating Clinical Evidence

paper_content:

Evidence-based decision making is becoming increasingly important in healthcare. Much valuable evidence is in the form of the results from clinical trials that compare the relative merits of treatments. For this, in previous papers, we have proposed a general framework for representing and synthesizing knowledge from clinical trials involving the same outcome indicator. Now, in this paper, we present a new framework for representing and synthesizing knowledge from clinical trials involving multiple outcome indicators. In this framework, evidence from randomized clinical trials, systematic reviews, meta-analyses, network analyses, etc., comparing a pair of treatments T1 and T2 according to desired and/or undesired outcomes is aggregated to give an overall evaluation of the treatments saying T1 is superior to T2, or T1 is equivalent to T2, or T1 is inferior to T2. Our general framework incorporates inference rules for generating arguments and counterarguments for claiming that one treatment is superior to another based on the available evidence, and preference rules for specifying which arguments are preferred. In this paper, we also present a new version of this framework that incorporates utility-theoretic criteria for defining specific preference rules over arguments.
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paper_title: Evidence-based guidelines and decision support services: a discussion and evaluation in triple assessment of suspected breast cancer

paper_content:

Widespread health service goals to improve consistency and safety in patient care have prompted considerable investment in the development of evidence-based clinical guidelines. Computerised decision support (CDS) systems have been proposed as a means to implement guidelines in practice. This paper discusses the general concept in oncology and presents an evaluation of a CDS system to support triple assessment (TA) in breast cancer care. Balanced-block crossover experiment and questionnaire study. One stop clinic for symptomatic breast patients. Twenty-four practising breast clinicians from United Kingdom National Health Service hospitals. A web-based CDS system. Clinicians made significantly more deviations from guideline recommendations without decision support (60 out of 120 errors without CDS; 16 out of 120 errors with CDS, P<0.001). Ignoring minor deviations, 16 potentially critical errors arose in the no-decision-support arm of the trial compared with just one (P=0.001) when decision support was available. Opinions of participating clinicians towards the CDS tool became more positive after they had used it (P<0.025). The use of decision support capabilities in TA may yield significant measurable benefits for quality and safety of patient care. This is an important option for improving compliance with evidence-based practice guidelines.
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paper_title: Argumentation theory in health care

paper_content:

Argumentation theory (AT) has been gaining momentum in the health care arena thanks to its intuitive and modular way of aggregating clinical evidence and taking rational decisions. The basic principles of argumentation theory are described and demonstrated in the breast cancer recurrence problem. It is shown how to represent available clinical evidence in arguments, how to define defeat relations among them and how to create a formal argumentation framework. Argumentation semantics are then applied over the built framework to compute arguments justification status. It is demonstrated how this process can enhance the clinician decision-making process. A encouraging predictive capacity is compared against the accuracy rate of well-established machine learning techniques confirming the potential of argumentation theory in health care.
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paper_title: On The Acceptability Of Arguments And Its Fundamental Role In Nonmonotonic Reasoning, Logic Programming And N-Persons Games

paper_content:

The purpose of this paper is to study the fundamental mechanism, humans use in argumentation, and to explore ways to implement this mechanism on computers. We do so by first developing a theory for argumentation whose central notion is the acceptability of arguments. Then we argue for the “correctness” or “appropriateness” of our theory with two strong arguments. The first one shows that most of the major approaches to nonmonotonic reasoning in AI and logic programming are special forms of our theory of argumentation. The second argument illustrates how our theory can be used to investigate the logical structure of many practical problems. This argument is based on a result showing that our theory captures naturally the solutions of the theory of n-person games and of the well-known stable marriage problem. By showing that argumentation can be viewed as a special form of logic programming with negation as failure, we introduce a general logic-programming-based method for generating meta-interpreters for argumentation systems, a method very much similar to the compiler-compiler idea in conventional programming. Keyword: Argumentation; Nonmonotonic reasoning; Logic programming; n-person games; The stable marriage problem
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paper_title: Argumentation-logic for creating and explaining medical hypotheses

paper_content:

Objective: While EIRA has proved to be successful in the detection of anomalous patient responses to treatments in the Intensive Care Unit, it could not describe to clinicians the rationales behind the anomalous detections. The aim of this paper is to address this problem. Methods: Few attempts have been made in the past to build knowledge-based medical systems that possess both argumentation and explanation capabilities. Here we propose an approach based on Dung's seminal calculus of opposition. Results: We have developed a new tool, arguEIRA, which is an extension of the existing EIRA system. In this paper we extend EIRA by providing it with an argumentation-based justification system that formalizes and communicates to the clinicians the reasons why a patient response is anomalous. Conclusion: Our comparative evaluation of the EIRA system against the newly developed tool highlights the multiple benefits that the use of argumentation-logic can bring to the field of medical decision support and explanation.
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paper_title: Safe and Sound: Artificial Intelligence in Hazardous Applications

paper_content:

Computer science and artificial intelligence are increasingly used in the hazardous and uncertain realms of medical decision making, where small faults or errors can spell human catastrophe. This book describes, from both practical and theoretical perspectives, an AI technology for supporting sound clinical decision making and safe patient management. The technology combines techniques from conventional software engineering with a systematic method for building intelligent agents. Although the focus is on medicine, many of the ideas can be applied to AI systems in other hazardous settings. The book also covers a number of general AI problems, including knowledge representation and expertise modeling, reasoning and decision making under uncertainty, planning and scheduling, and the design and implementation of intelligent agents.The book, written in an informal style, begins with the medical background and motivations, technical challenges, and proposed solutions. It then turns to a wide-ranging discussion of intelligent and autonomous agents, with particular reference to safety and hazard management. The final section provides a detailed discussion of the knowledge representation and other aspects of the agent model developed in the book, along with a formal logical semantics for the language.
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paper_title: Argumentation Theory for Decision Support in Health-Care: A Comparison with Machine Learning

paper_content:

This study investigates role of defeasible reasoning and argumentation theory for decision-support in the health-care sector. The main objective is to support clinicians with a tool for taking plausible and rational medical decisions that can be better justified and explained. The basic principles of argumentation theory are described and demonstrated in a well known health scenario: the breast cancer recurrence problem. It is shown how to translate clinical evidence in the form of arguments, how to define defeat relations among them and how to create a formal argumentation framework. Acceptability semantics are then applied over this framework to compute arguments justification status. It is demonstrated how this process can enhance clinician decision-making. A well-known dataset has been used to evaluate our argument-based approach. An encouraging 74% predictive accuracy is compared against the accuracy of well-established machine-learning classifiers that performed equally or worse than our argument-based approach. This result is extremely promising because not only demonstrates how a knowledge-base paradigm can perform as well as state-of-the-art learning-based paradigms, but also because it appears to have a better explanatory capacity and a higher degree of intuitiveness that might be appealing to clinicians.
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paper_title: Harnessing Ontologies for Argument-Based Decision-Making in Breast Cancer

paper_content:

We introduce a novel Ontology-based Argumentation Framework (OAF) that links a logic-based argumentation formalism and description logic ontologies. We show how these two formalisms can be tightly coupled by observing a few simple restrictions, and provides features not available in either formalism alone. Our work is evaluated in a large case study on decision-making in treatment choice in breast cancer, where rules are developed from the results of published clinical trials, and we present a small subset of this to demonstrate the use of the system. We show that OAF provides five advantages: (1) facilitating the clear use of shared definitions between multiple authors; (2) enabling us to match terms in the ontology and rules with those in the specific domain literature; (3) providing a close fit between structure of clinical trials and the structure of our rules; (4) delivering significant economies in the size of the rule-base compared to existing approaches; (5) allowing us take advantage of developments in both ontological and argumentative approaches. We also demonstrate that even a restricted language such as ours is sufficient to capture enough information to generate arguments that are useful for clinical practice. An early prototype implementation is available.
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paper_title: Argumentation-Based Inference and Decision Making--A Medical Perspective

paper_content:

The argumentation services platform with integrated components (Aspic) project aims to provide advanced argumentation-based computational capabilities. Argumentation is a potentially important paradigm for developing commercial and public services that are flexible and easily understood by human users.
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paper_title: Argumentation in Decision Support for Medical Care Planning for Patients and Clinicians.

paper_content:

Developing a care plan for a patient requires an understanding of interactions and dependencies between procedures, and of their possible outcomes for an individual patient, and it requires the planner to keep track of this information as the proposed plan evolves. This is difficult even for experienced clinicians, but increasingly patients are expected (and expect) to participate. We describe an argumentation-based planning support system designed to ameliorate the cognitive load imposed by the planning and communication elements of such tasks. An initial evaluation study in the field of genetic counseling produced promising results. The approach may provide a general aid for clinicians and patients in visualizing, customizing, evaluating and communicating about care plans.
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paper_title: Defeasible reasoning with variable degrees of justification

paper_content:

The question addressed in this paper is how the degree of justification of a belief is determined. A conclusion may be supported by several different arguments, the arguments typically being defeasible, and there may also be arguments of varying strengths for defeaters for some of the supporting arguments. What is sought is a way of computing the "on sum" degree of justification of a conclusion in terms of the degrees of justification of all relevant premises and the strengths of all relevant reasons. I have in the past defended various principles pertaining to this problem. In this paper I reaffirm some of those principles but propose a significantly different final analysis. Specifically, I endorse the weakest link principle for the computation of argument strengths. According to this principle the degree of justification an argument confers on its conclusion in the absence of other relevant arguments is the minimum of the degrees of justification of its premises and the strengths of the reasons employed in the argument. I reaffirm my earlier rejection of the accrual of reasons, according to which two arguments for a conclusion can result in a higher degree of justification than either argument by itself. This paper diverges from my earlier theory mainly in its treatment of defeaters. First, it argues that defeaters that are too weak to defeat an inference outright may still diminish the strength of the conclusion. Second, in the past I have also denied that multiple defeaters can result in the defeat of an argument that is not defeated by any of the defeaters individually. In this paper I urge that there are compelling examples that support a limited version of this "collaborative" defeat. The need to accommodate diminishers and collaborative defeat has important consequences for the computation of degrees of justification. The paper proposes a characterization of degrees of justification that captures the various principles endorsed and constructs an algorithm for computing them.
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paper_title: Towards a general model for argumentation services

paper_content:

LA is a formal Logic of Argument which was originally developed as a flexible foundation for knowledge-level decision models, and to facilitate explanation and userinterface design. The logic has a clear semantics and is embodied in the PROforma language, a simple but effective representation for modeling decisions, plans and software agents. ASPIC is an EU funded project1 that aims to develop a general model for argumentation services (www.argumentation.org) including a consensus semantics and interchange format for argumentation in inference, decision-making, dialogue and learning. ASPIC is also providing an opportunity to extend PROforma to support multi-agent services. This is being used to implement a wide range of services in multidisciplinary cancer care (ttp://acl.icnet.uk/credoweb).
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Title: Defeasible Reasoning and Argument-Based Systems in Medical Fields: An Informal Overview

Section 1: INTRODUCTION
Description 1: In this section, discuss the significance of defeasible reasoning in medical systems, describe the concept of default knowledge and its application, and introduce non-monotonic logic, including terminologies and examples.

Section 2: ARGUMENTATION THEORY
Description 2: Provide an overview of argumentation theory, its multidisciplinary aspects, and its importance in computational models of defeasible reasoning. Describe the different models of arguments including monological, dialogical, and rhetorical models, and introduce the structure upon which argument-based systems are built.

Section 3: ARGUMENT-BASED APPLICATIONS IN THE MEDICAL AND HEALTH CARE SECTOR
Description 3: Highlight various applications of defeasible reasoning and argumentation theory in the medical and healthcare sectors. Provide examples and case studies to show their practical utility in areas such as treatment support, genetic counseling, group decision support, and cancer recurrence prediction.

Section 4: CONCLUSION
Description 4: Summarize the key points discussed in the paper, reiterate the benefits of using defeasible reasoning and argumentation theory in medical fields, and promote the adoption of these techniques while encouraging comparisons with traditional decision-support methods.