ABSTRACT. The paper introduces a general model for the study of decomposability in abstract argumentation, i.e. the possibility of determining the semantics outcome based on local evaluations in subframeworks. As such, the paper extends a previous work by generalizing over the kind of information locally exploited. While not concerned with specific semantics, the paper shows the range of decomposable semantics with varying degrees of local information. It also introduces the notion of a canonical local function, which can enforce decomposability whenever this is possible.

ABSTRACT. Base argumentation is an logic-based instantiation of abstract argumentation. Each base argument is a subset of the given knowledge base. In this paper, we show that base argumentation satisfies some rationality postulates and prove some correspondence results between base argumentation and deductive argumentation. With the correspondence results, base argumentation can be seen as an abstraction of deductive argumentation.

ABSTRACT. In abstract argumentation, multiple argumentation semantics for choosing sets of jointly acceptable arguments have been defined. In the principle-based approach, multiple principles have been proposed and formalized in order to guide the choice for a semantics and the search for new semantics. Admissibility is a central principle satisfied by many semantics, including complete, stable, grounded and preferred. A more recently introduced principle is the INRA principle, motivated by considerations about the relevance of arguments and supported by a cognitive study. This paper additionally introduces and motivates the SAFWOC principle in order to positively distinguish less abstention-friendly semantics like preferred and stable from more abstention-friendly semantics like grounded and complete. After observing that no existing semantics satisfies these three principles, we define the novel choice-preferred semantics that satisfies the three principles. Additionally we show that choice-preferred satisfies further desirable principles like existence, directionality, SCC-recursiveness and completeness.

ABSTRACT. Baumann, Brewka and Ulbricht recently introduced weak admissibility as an alternative to Dung’s notion of admissibility, and they use it to define weakly preferred, weakly complete and weakly grounded semantics of argumentation frameworks. In earlier work we introduced two variants of their new semantics, which we called qualified and semi-qualified semantics, and we analyzed all known variants of weak admissibility semantics with respect to some of the principles discussed in the literature on abstract argumentation, as well as with respect to some new principles we introduced to distinguish all of them. Besides selecting a semantics for an application, or for algorithmic design, such a principle-based analysis can also be used for the further search for weak admissibility semantics. In this paper we introduce six new kinds of semantics based on weak admissibility, and we provide an initial principle-based analysis. The analysis illustrates various ways in which the new semantics improve on the existing ones.

ABSTRACT. The issue of how a semantics should deal with self-attacking arguments was always a subject of debate amongst argumentation scholars. A consensus exists for extension-based semantics because those arguments are always rejected (as soon as the semantics in question respect conflict-freeness). In case of gradual semantics, the question is more complex, since other criteria are taken into account. A way to check the impact of these arguments is to use the principles (i.e. desirable properties to be satisfied by a semantics) from the literature. Principles like Self-Contradiction and Strong Self-Contradiction prescribe how to deal with self-attacking arguments. We show that they are incompatible with the well-known Equivalence principle (which is satisfied by almost all the existing gradual semantics), as well as with some other principles (e.g.\ Counting). This incompatibility was not studied until now and the class of semantics satisfying Self-Contradiction is under-explored. In the present paper, we explore that class of semantics. We show links and incompatibilities between several principles. We define a semantics that satisfies (Strong) Self-Contradiction and a maximal number of compatible principles. We introduce an iterative algorithm to calculate our semantics and prove that it always converges. We also provide a characterisation of our semantics. Finally, we experimentally show that our semantics is computationally efficient.

ABSTRACT. Judgment documents contain rich legal information, they are simultaneously lengthy with complex structure. This requires summarizing judgment documents in an effective way. By analyzing the structural features of Chinese judgment documents, we propose an automatic summarization method, which consists of an extraction model and an abstraction model. In the extraction model, all the sentences are encoded by a Self-Attention network and are classified into key sentences and non-key sentences. The key sentences, whose functions are defined as cause of action, facts, issue, ratio of the decision, ruling basis and final judgment by the Chinese court, are extracted as an initial summarization. In the abstraction model, the initial summarization is refined into a final summarization by a unidirectional-bidirectional attention network. Such a summarization method retains most of the important legal information while keeping the context concise and brief. Moreover, this method could help improve the efficiency in case handling and make judgment documents more accessible to the general readers. The experimental results on CAIL2020 dataset are satisfactory.

ABSTRACT. Collective argumentation studies how to reach a collective decision that is acceptable to the group in a debate. I introduce the concept of topological restriction to enrich collective argumentation. Topological restrictions are rational constraints assumed to be satisfied by individual agents. We assume that in a debate, for every pair of arguments that are being considered, every agent indicates whether the first one attacks the second, i.e., an agent’s argumentative stance is characterized as an argumentation framework, and only argumentation frameworks that satisfy topological constraints are allowed. The topological constraints we consider in this paper include acyclicity, symmetry, as well as a newly defined topological property called t-self-defense. We show that when the profile of argumentation frameworks provided by agents satisfies topological restrictions, impossibility results during aggregation can be avoided. Furthermore, if a profile is topological-restricted with respect to t-self-defense, then the majority rule guarantees admissibility during aggregation.

ABSTRACT. Assumption-based argumentation (ABA) is one of the main general frameworks for structured argumentation. Dispute derivations for ABA allow for evaluating claims in a dialectical manner: i.e. on the basis of an exchange of arguments and counter-arguments for a claim between a proponent and an opponent of the claim. Current versions of dispute derivations are geared towards determining (credulous) acceptance of claims w.r.t. the admissibility-based semantics that ABA inherits from abstract argumentation. Relatedly, they make use of backwards or top down reasoning for constructing arguments. In this work we define flexible dispute derivations with forward as well as backward reasoning allowing us, in particular, to also have dispute derivations for finding admissible, complete, and stable assumption sets rather than only determine acceptability of claims. We give an argumentation-based definition of such dispute derivations and a more implementation friendly alternative representation in which disputes involve exchange of claims and rules rather than arguments. These can be seen as elaborations on, in particular, existing graph-based dispute derivations on two fronts: first, in also allowing for forward reasoning; second, in that all arguments put forward in the dispute are represented by a graph and not only the proponents.

ABSTRACT. We examine requirements for representing the semantics of text in logic, by study- ing a sample of several balanced corpora. Our method is to create lists of words and sentential constructs that can easily be assessed in text, which are then mapped to requirements for logics of different expressiveness. We then run an automated analysis on thousands of sentences from two English corpora and manually validate a sample.