The paper “A Characterization of ASPIC+ Frameworks in Sequent-Based Formal Argumentation” by Kees van Berkel, Luca Redondi and Christian Straßer has been published in the proceedings of LNGAI 2026. Here’s the abstract:
Structured argumentation frameworks like ASPIC+ and sequent-based systems offer contrasting yet complementary approaches to defeasible reasoning. While ASPIC+ relies on proof trees to track argument structure —a necessity for applying preference principles like weakest link and last link— sequent-based approaches represent arguments as flat premise-conclusion pairs, sacrificing this structural detail for brevity. This paper establishes a formal bridge between these paradigms by proposing a sequent-based characterization of ASPIC+ that internalizes reasoning with priorities directly into the argument generation process, thus bypassing the need for proof trees. We introduce a generalized sequent calculus where inference rules are indexed with strength metrics, allowing argument strength to be computed and embedded upon rule application. This mechanism ensures that preference relations transform attacks into defeats during derivation, rather than by external evaluation. This work not only clarifies the relationship between tree-based and sequent-based argumentation but also provides a unified framework for handling structured preferences.