提出一种更精准的查询抽象方法，提升知识库查询效率与准确性。
Abstractions of Queries in Ontology-Based Data Access
- 通过扩展查询语言，实现对数据查询在本体层的精确抽象。
- 证明该方法能表达最完整抽象，完美时可达理想结果。
- 连接数据交换中的最大恢复概念，提升抽象合理性，适合数据库研究者。
在基于本体的数据访问（OBDA）中，多个数据源通过映射整合到一个本体中。本文研究基于存在性规则和确定性答案语义的查询抽象问题。由于完全抽象可能不存在，引入了最小完备和最大保真抽象的概念。本文在扩展的无交集查询（UCQs）基础上，加入有限不等式和标记数据库常量的特殊谓词，虽未增加计算复杂度，但能表达最小完备抽象，从而在存在时实现完美抽象。同时，通过与数据交换中的最大恢复概念建立新联系，刻画了最大保真抽象。
原文摘要 · Abstract (English)
In ontology-based data access (OBDA), multiple data sources are integrated via mappings to an ontology. We consider an OBDA setting based on existential rules and the certain answer semantics. We address the recent issue of query abstraction, which consists of abstracting data queries by translating them to the ontology layer. Since a perfect abstraction may not exist, the notions of minimally complete and maximally sound abstractions have been introduced. We study abstractions within an extension of UCQs with a limited form of inequality and a special predicate marking database constants. While this extension does not lead to an increased complexity of the problems of interest, it is able to express minimally complete abstractions, hence perfect abstractions when they exist. We also characterize maximally sound abstractions by making a new connection with the notion of maximum recovery stemming from data exchange.
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