Phan Minh Thang

Towards a Common Framework for Dialectical Proof Procedures in Abstract Argumentation

We present a common framework for dialectical proof procedures for computing credulous, grounded, ideal and sceptical preferred semantics of abstract argumentation. The framework is based on the notions of dispute derivation and base derivation. Dispute derivation is a dialectical notion first introduced for computing credulous semantics in assumption-based argumentation, and adapted here for computing credulous semantics and grounded semantics. Base derivation is introduced for two purposes: (i) to characterize all preferred extensions containing a given argument, and (ii) to represent backtracking in the search for a dispute derivation. We prove the soundness of the proof procedures for any argumentation frameworks and their completeness for general classes of finitary or finite-branching argumentation frameworks containing the class of finite argumentation frameworks as a subclass.We also discuss related results.

Closure and consistency in logic-associated argumentation

Properties like logical closure and consistency are important properties in any logical reasoning system. Caminada and Amgoud showed that not every logic-based argument system satisfies these relevant properties. But under conditions like closure under contraposition or transposition of the monotonic part of the underlying logic, ASPIC-like systems satisfy these properties. In contrast, the logical closure and consistency properties are not well-understood for other well-known and widely applied systems like logic programming or assumption based argumentation. Though conditions like closure under contraposition or transposition seem intuitive in ASPIC-like systems, they rule out many sensible ASPIClike systems that satisfy both properties of closure and consistency. We present a new condition referred to as the self-contradiction axiom that guarantees the consistency property in both ASPIC-like and assumption-based systems and is implied by both properties of closure under contraposition or transposition. We develop a logicassociated abstract argumentation framework, by associating abstract argumentation with abstract logics to represent the conclusions of arguments. We show that logicassociated abstract argumentation frameworks capture ASPIC-like systems (without preferences) and assumption-based argumentation. We present two simple and natural properties of compactness and cohesion in logic-associated abstract argumentation frameworks and show that they capture the logical closure and consistency properties. We demonstrate that in both assumption-based argumentation and ASPIC-like systems, cohesion follows naturally from the self-contradiction axiom. We further give a translation from ASPIC-like systems (without preferences) into equivalent assumption-based systems that keeps the selfcontradiction axiom invariant.

Modular Argumentation For Modelling Legal Doctrines in Common Law of Contract

To create a programming environment for contract dispute resolution, we propose an extension of assumption-based argumentation into modular assumption-based argumentation in which different modules of argumentation representing different knowledge bases for reasoning about beliefs and facts and for representation and reasoning with the legal doctrines could be built and assembled together. A distinct novel feature of modular argumentation in compare with other modular logic-based systems like Prolog is that it allows references to different semantics in the same module at the same time, a feature critically important for application of argumentation in legal domains like contract dispute resolution where the outcomes of court cases often depend on whether credulous or skeptical modes of reasoning were applied by the contract parties. We apply the new framework to model the doctrines of contract breach and mutual mistake.

Argument-Based Decision Making and Negotiation in E-Business: Contracting a Land Lease for a Computer Assembly Plant

We describe an extensive application of argument-based decision making and negotiation to a real-world scenario in which an investor agent and an estate manager agent negotiate to lease a land for a computer assembly factory. Agents are equipped with beliefs, goals, preferences, and argument-based decision-making mechanisms taking uncertainties into account. Goals are classified as either structural or contractual. The negotiation process is divided into two phases. In the first phase, following a recently proposed framework [8] the investor agent find suitable locations based on its structural goals such as requirements about transportation; the estate manager agent determines favored tenants based on its structural goals such as requirements about resource conservation. In the second phase, we introduce a new novel argument-based negotiation protocol for agents to agree on contract to fulfill their contractual goals such as waste disposal cost.

Modular argumentation for modelling legal doctrines of performance relief

Legal doctrines provide principles, guidelines and rules for dispute resolution in reasoning with cases. To apply legal doctrines, the context of a contract consisting of different knowledge bases about beliefs and expertise of contract parties as well as about common social, legal domains need to be established. Judges then decide legal outcomes by reasoning from factors drawn in contract contexts following legal doctrines. In this paper, we model this decision making by modular argumentation. We focus on legal doctrines in contract law, especially the doctrines of impossibility and frustration of purpose.

Inductive Defense for Sceptical Semantics of Extended Argumentation

An abstract argumentation framework may have many extensions. Which extension should be adopted as the semantics depends on the sceptical attitudes of the reasoners. Different degrees of scepticism lead to different semantics ranging from the grounded extension as the most sceptical semantics to preferred extensions as the least sceptical semantics. Extending abstract argumentation to allow attacks to be attacked, subjects attacks to argumentation and hence gives rise to a new dimension of scepticism for characterizing how sceptically attacks are accepted. In this article, we present a semantics based on the notion of inductive (grounded) defense of attacks which is sceptical towards the acceptance of attacks but credulous towards the acceptance of arguments.We show that the semantics preserves fundamental properties of abstract argumentation including the monotonicity of the characteristic function. We further show that any extension of the semantics proposed by Gabbay; Baroni, Cerutti, Giacomin and Guida; and Modgil contains a sceptical part being an extension of our semantics, and a credulous part resulted from its credulousness towards the acceptance of attacks. We then introduce a stratified form of extended argumentation which still allows an unbounded number of levels of attacks against attacks while assuring that all proposed semantics coincide. In this article, we also develop a sound and complete dialectical proof procedure for the presented semantics following a model of dispute that alternates between argumentation to accept arguments and to accept attacks.

Dialectical Proof Procedures for Probabilistic Abstract Argumentation

A dialectical proof procedure for computing grounded semantics of probabilistic abstract argumentation is presented based on the notion of probabilistic dispute tree. We also present an algorithm for top-down construction of probabilistic dispute trees.

Trust Negotiation with Nonmonotonic Access Policies

We study the structure of nonmonotonic access policies for internet-based resources. We argue that such policies could be divided into two parts: the locally designed policies and imported policies. Imported policies should always be monotonic while the local policies could be nonmonotonic. We develop a safe proof procedure for nonmonotonic trust negotiation where safety means that access to a resource is granted only if its access policy is satisfied.

Argumentation-Based Semantics for Logic Programs with First-Order Formulae

This paper studies different semantics of logic programs with first order formulae under the lens of argumentation framework. It defines the notion of an argumentation-based answer set and the notion of an argumentation-based well-founded model for programs with first order formulae. The main ideas underlying the new approach lie in the notion of a proof tree supporting a conclusion given a program and the observation that proof trees can be naturally employed as arguments in an argumentation framework whose stable extensions capture the program’s well-justified answer semantics recently introduced in [23]. The paper shows that the proposed approach to dealing with programs with first order formulae can be easily extended to a generalized class of logic programs, called programs with FOL-representable atoms, that covers various types of extensions of logic programming proposed in the literature such as weight constraint atoms, aggregates, and abstract constraint atoms. For example, it shows that argumentation-based well-founded model is equivalent to the well-founded model in [27] for programs with abstract constraint atoms. Finally, the paper relates the proposed approach to others and discusses possible extensions.

Enhancing the employability of IT graduates in Vietnam

Purpose – The purpose of this paper is to identify the key determinants of employability of information technology (IT) graduates in Vietnam and examines their impact on self-perceived employability and the duration of the job search. Design/methodology/approach – This study is based on data collected from the responses to an online survey from more than 500 IT graduates from different higher education institutions in Vietnam. Employability, its outcome and its key determinants were integrated into one model. Exploratory factor, confirmatory factor and path analyses were conducted to test the model by means of structural equation modeling. Findings – The self-perceived employability of IT graduates in Vietnam was determined by graduates’ English language skills, soft skills, adaptability skills, the quality of the institution’s IT program and job seeking efforts. Results also indicated that work experience, professional competencies and employability made the job search duration shorter, but job seeking e...