In this paper, we explore the issue of inconsistency handling over prioritized knowledge bases (KBs), which consist of an ontology, a set of facts, and a priority relation between conflicting facts. In the database setting, a closely related scenario has been studied and led to the definition of three different notions of optimal repairs (global, Pareto, and completion) of a prioritized inconsistent database. After transferring the notions of globally-, Pareto- and completion-optimal repairs to our setting, we study the data complexity of the core reasoning tasks: query entailment under inconsistency-tolerant semantics based upon optimal repairs, existence of a unique optimal repair, and enumeration of all optimal repairs. Our results provide a nearly complete picture of the data complexity of these tasks for ontologies formulated in common DL-Lite dialects. The second contribution of our work is to clarify the relationship between optimal repairs and different notions of extensions for (set-based) argumentation frameworks. Among our results, we show that Pareto-optimal repairs correspond precisely to stable extensions (and often also to preferred extensions), and we propose a novel semantics for prioritized KBs which is inspired by grounded extensions and enjoys favourable computational properties. Our study also yields some results of independent interest concerning preference-based argumentation frameworks.

翻译：本文探讨了优先知识库（KBs）的不一致性处理问题，此类知识库由本体、事实集以及冲突事实间的优先关系构成。在数据库研究领域，一个密切相关的场景已被探讨，并由此导出了优先不一致数据库的三种不同最优修复概念（全局最优、帕累托最优与完备最优）。在将全局最优、帕累托最优与完备最优修复的概念迁移至我们的研究框架后，我们分析了核心推理任务的数据复杂性：包括基于最优修复的容错语义下的查询蕴涵、唯一最优修复的存在性判定以及所有最优修复的枚举。我们的研究结果针对采用常见DL-Lite方言表述的本体，为这些任务的数据复杂性提供了近乎完整的图景。本研究的第二个贡献在于厘清了最优修复与（基于集合的）论证框架中不同外延概念之间的关系。研究结果表明，帕累托最优修复精确对应于稳定外延（通常也对应于优选外延），并提出了一种受基外延启发、具有良好计算性质的优先知识库新语义。我们的研究还获得了关于基于偏好的论证框架的若干独立意义的结果。