We consider the dichotomy conjecture for consistent query answering under primary key constraints. It states that, for every fixed Boolean conjunctive query q, testing whether q is certain (i.e. whether it evaluates to true over all repairs of a given inconsistent database) is either polynomial time or coNP-complete. This conjecture has been verified for self-join-free and path queries. We show that it also holds for queries with two atoms.

翻译：我们研究主键约束下一致性查询回答的二分猜想。该猜想指出：对于任意固定的布尔合取查询q，判断q是否确定成立（即是否在所有给定不一致数据库的修复上均评估为真）要么是多项式时间可解的，要么是coNP完全的。该猜想已被证明对无自连接查询和路径查询成立。我们证明该猜想对含有两个原子的查询同样成立。