论文标题
一致的查询回答主要键和连接性查询，并进行计数
Consistent Query Answering for Primary Keys and Conjunctive Queries with Counting
论文作者
论文摘要
近年来，已经深入研究了对主要键和无自结合的查询的始终查询答案的问题，到现在为止。在本文中，我们研究了该问题的扩展。我们考虑的查询计算了每个值的答案（可能是复合）列的每个值的次数，该列是完整连接查询的答案。在数据库维修的设置中，我们采用了[Arenas等，ICDT 2001]的语义，该语义在这些计数上计算紧密的下限和上限，在这些计数中，在所有维修中都进行了界限。 Ariel Fuxman在他的博士学位论文中定义了一个句法类别的查询类，称为C_Forest，可以通过执行两个一阶查询（一个用于下限，一个用于上限），然后进行简单的计数步骤来完成此计算。我们将术语“简约的计数”用于此计算。一个自然的问题是，C_Forest是否包含所有无自结合的连词查询，这些查询承认了简约的计数。我们对这个问题负面回答。我们定义了一种称为c_parsimony的新句法类别类别，并证明它包含所有（唯一的）无自结合的连词查询，这些查询允许逐渐计算。
The problem of consistent query answering for primary keys and self-join-free conjunctive queries has been intensively studied in recent years and is by now well understood. In this paper, we study an extension of this problem with counting. The queries we consider count how many times each value occurs in a designated (possibly composite) column of an answer to a full conjunctive query. In a setting of database repairs, we adopt the semantics of [Arenas et al., ICDT 2001] which computes tight lower and upper bounds on these counts, where the bounds are taken over all repairs. Ariel Fuxman defined in his PhD thesis a syntactic class of queries, called C_forest, for which this computation can be done by executing two first-order queries (one for lower bounds, and one for upper bounds) followed by simple counting steps. We use the term "parsimonious counting" for this computation. A natural question is whether C_forest contains all self-join-free conjunctive queries that admit parsimonious counting. We answer this question negatively. We define a new syntactic class of queries, called C_parsimony, and prove that it contains all (and only) self-join-free conjunctive queries that admit parsimonious counting.
