An informant-based approach to argument strength in Defeasible Logic Programming

This work formalizes an informant-based structured argumentation approach in a multi-agent setting, where the knowledge base of an agent may include information provided by other agents, and each piece of knowledge comes attached with its informant. In that way, arguments are associated with the set of informants corresponding to the information they are built upon. Our approach proposes an informant-based notion of argument strength, where the strength of an argument is determined by the credibility of its informant agents. Moreover, we consider that the strength of an argument is not absolute, but it is relative to the resolution of the conflicts the argument is involved in. In other words, the strength of an argument may vary from one context to another, as it will be determined by comparison to its attacking arguments (respectively, the arguments it attacks). Finally, we equip agents with the means to express reasons for or against the consideration of any piece of information provided by a given informant agent. Consequently, we allow agents to argue about the arguments’ strength through the construction of arguments that challenge (respectively, defeat) or are in favour of their informant agents.Fil: Cohen, Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; ArgentinaFil: Gottifredi, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; ArgentinaFil: Tamargo, Luciano Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; ArgentinaFil: García, Alejandro Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; ArgentinaFil: Simari, Guillermo Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; Argentin

On Elitist Lifting and Consistency in Structured Argumentation

We address the question of how to lift an ordering over rules to an ordering over arguments (sets of rules) that is well-behaved. It has been shown that so-called elitist lifting may lead to inconsistencies. We give restrictions on the underlying rule-ordering that avoid inconsistency. Then we show that a recently proposed solution – so-called disjoint strict lifting – that was introduced to address conceptual objections, also leads to inconsistency. We show that another recent proposal, telling us to reorder rule-orderings to take argument structure into account before lifting, is able to avoid conceptual problems without leading to any new inconsistencies. We generalise this approach by defining what we call structural rule-orderings and show a correspondence between weakest link and last link lifting of such orderings, which has interesting consequences for the question of consistency. We arrive at our results using a signature-based approach to structured argumentation. Instead of settling on a given framework, such as ASPIC+, we define an argumentation language that allows us to express only those properties of argumentation systems we need to establish our results. This abstract approach simplifies and clarifies the technical work while making our contribution more general

On Elitist Lifting and Consistency in Structured Argumentation

We address the question of how to lift an ordering over rules to an ordering over arguments (sets of rules) that is well-behaved. It has been shown that so-called elitist lifting may lead to inconsistencies. We give restrictions on the underlying rule-ordering that avoid inconsistency. Then we show that a recently proposed solution – so-called disjoint strict lifting – that was introduced to address conceptual objections, also leads to inconsistency. We show that another recent proposal, telling us to reorder rule-orderings to take argument structure into account before lifting, is able to avoid conceptual problems without leading to any new inconsistencies. We generalise this approach by defining what we call structural rule-orderings and show a correspondence between weakest link and last link lifting of such orderings, which has interesting consequences for the question of consistency. We arrive at our results using a signature-based approach to structured argumentation. Instead of settling on a given framework, such as ASPIC+, we define an argumentation language that allows us to express only those properties of argumentation systems we need to establish our results. This abstract approach simplifies and clarifies the technical work while making our contribution more general