论文标题
一致查询主要钥匙和一键外钥匙的二分法
A Dichotomy in Consistent Query Answering for Primary Keys and Unary Foreign Keys
论文作者
论文摘要
自2005年以来，在对主要密钥的一致查询答案（CQA）的问题中取得了重大进展。在此问题中，输入是一个数据库实例，可能违反一个或多个主要的密钥约束。维修定义为满足所有主要键的最大子启动。考虑到布尔查询Q，问题是Q在每次维修中是否都正确。 到目前为止，尽管在数据库系统中参考完整性的重要性，但该领域的理论研究尚未解决主要密钥和外键约束的组合。本文解决了CQA在主键和外键方面的问题。在这种情况下，很自然地采用对称差异维修的概念，因为可以通过插入新元素来修复外键。 我们考虑了外国键是一致的情况，并且查询是无自结合的连接性查询。在这种情况下，我们表征了那些接受一致一阶重写的CQA问题与不承认一致的问题之间的边界。
Since 2005, significant progress has been made in the problem of Consistent Query Answering (CQA) with respect to primary keys. In this problem, the input is a database instance that may violate one or more primary key constraints. A repair is defined as a maximal subinstance that satisfies all primary keys. Given a Boolean query q, the question then is whether q holds true in every repair. So far, theoretical research in this field has not addressed the combination of primary key and foreign key constraints, despite the importance of referential integrity in database systems. This paper addresses the problem of CQA with respect to both primary keys and foreign keys. In this setting, it is natural to adopt the notion of symmetric-difference repairs, because foreign keys can be repaired by inserting new tuples. We consider the case where foreign keys are unary, and queries are conjunctive queries without self-joins. In this setting, we characterize the boundary between those CQA problems that admit a consistent first-order rewriting, and those that do not.
