Reasoning on defeasible knowledge is a topic of interest in the area of description logics, as it is related to the need of representing exceptional instances in knowledge bases. In this direction, in our previous works we presented a framework for representing (contextualized) OWL RL knowledge bases with a notion of justified exceptions on defeasible axioms: reasoning in such framework is realized by a translation into ASP programs. The resulting reasoning process for OWL RL, however, introduces a complex encoding in order to capture reasoning on the negative information needed for reasoning on exceptions. In this paper, we apply the justified exception approach to knowledge bases in , that is, the language underlying OWL QL. We provide a definition for knowledge bases with defeasible axioms and study their semantic and computational properties. In particular, we study the effects of exceptions over unnamed individuals. The limited form of axioms allows us to formulate a simpler ASP encoding, where reasoning on negative information is managed by direct rules. The resulting materialization method gives rise to a complete reasoning procedure for instance checking in with defeasible axioms.1

对可废止知识进行推理是描述逻辑领域的一个热门话题，因为它与在知识库中表示异常实例的需求有关。在这个方向上，在我们之前的工作中，我们提出了一个框架，用于表示（上下文化的）OWL RL 知识库，其中包含关于可废止公理的合理例外的概念：这种框架中的推理是通过翻译成 ASP 程序来实现的。然而，由此产生的 OWL RL 推理过程引入了复杂的编码，以便捕获对异常推理所需的负面信息的推理。在本文中，我们将正当异常方法应用于知识库，即 OWL QL 的底层语言。我们提供了一个定义具有可废止公理的知识库，并研究它们的语义和计算特性。特别是，我们研究了异常对未命名个人的影响。公理的有限形式允许我们制定更简单的 ASP 编码，其中对负面信息的推理由直接规则管理。由此产生的物化方法产生了一个完整的推理过程，例如检查可废止的公理。1