Ontology-mediated query answering (OMQA) is a promising approach to data access and integration that has been actively studied in the knowledge representation and database communities for more than a decade. The vast majority of work on OMQA focuses on conjunctive queries, whereas more expressive queries that feature counting or other forms of aggregation remain largely unex-plored. In this paper, we introduce a general form of counting query, relate it to previous proposals, and study the complexity of answering such queries in the presence of DL-Lite ontologies. As it follows from existing work that query answering is intractable and often of high complexity, we consider some practically relevant restrictions, for which we establish improved complexity bounds.

中文翻译：

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在 DL-Lite 本体上回答计数查询

本体介导的查询回答 (OMQA) 是一种很有前途的数据访问和集成方法，十多年来一直在知识表示和数据库社区中得到积极研究。OMQA 的绝大多数工作都集中在联合查询上，而具有计数或其他形式聚合功能的更具表现力的查询在很大程度上仍未得到探索。在本文中，我们介绍了一种计数查询的一般形式，将其与之前的提议相关联，并研究了在存在 DL-Lite 本体的情况下回答此类查询的复杂性。由于从现有工作中得出，查询回答是棘手的并且通常具有很高的复杂性，因此我们考虑了一些实际相关的限制，为此我们建立了改进的复杂性界限。