Dung's abstract argumentation frameworks model acceptability solely in terms of an attack relation, thereby conflating two conceptually distinct aspects of argumentative reasoning: direct conflict between arguments and the structural dependencies that arise from their internal composition. While this abstraction preserves extension-based semantics, it obscures how justification is grounded in subarguments and how defeats propagate through argument structure. We introduce Subargument Argumentation Frameworks (SAFs), an abstract framework in which direct attack and subargumenthood are represented as independent primitive relations. This separation makes structural dependency explicit at the representational level while leaving its semantic impact to be determined by structure-sensitive notions of defence, admissibility, and complete semantics defined within the framework. We show that projecting SAFs onto attack-only frameworks yields extension-equivalent Dung frameworks under all standard semantics, yet the projection irreversibly loses information about justificatory grounding and structural propagation. SAFs therefore provide strictly greater representational expressiveness while remaining semantically compatible with Dung's theory, thereby offering a principled basis for structure-sensitive accounts of defence, justification, and explanation in abstract argumentation.

翻译：董氏抽象论辩框架仅通过攻击关系来建模可接受性，从而混淆了论证推理中两个概念上不同的方面：论证之间的直接冲突及其内部构成所产生的结构依赖性。虽然这种抽象保留了基于扩展的语义，但它模糊了证成如何在子论证中奠基以及击败如何通过论证结构传播。我们引入子论证论辩框架（SAFs），这是一种抽象框架，其中直接攻击和子论证关系被表示为独立的原始关系。这种分离在表示层面使结构依赖性显式化，同时将其语义影响留给框架内定义的结构敏感的防御、可容许性和完全语义来确定。我们证明，将SAFs投影到纯攻击框架上，在所有标准语义下都能产生扩展等价的董氏框架，然而这种投影会不可逆地丢失关于证成奠基和结构传播的信息。因此，SAFs在提供严格更大的表示表达能力的同时，在语义上与董氏理论保持兼容，从而为抽象论辩中结构敏感的防御、证成和解释提供了原则性基础。