We study the problem to decide, given sets T1,T2 of tuple-generating dependencies (TGDs), also called existential rules, whether T2 is a conservative extension of T1. We consider two natural notions of conservative extension, one pertaining to answers to conjunctive queries over databases and one to homomorphisms between chased databases. Our main results are that these problems are undecidable for linear TGDs, undecidable for guarded TGDs even when T1 is empty, and decidable for frontier-one TGDs.
翻译：我们研究这个问题,以决定,鉴于T1,T2设置了产生图普尔依赖性的T1,T2(TGDs),它也称为生存规则,T2是否是保守的T1的延伸。 我们考虑保守扩展的两个自然概念,一个是数据库合并查询的答案,另一个是被追踪的数据库之间的同质性概念。我们的主要结果是,这些问题对于线性TGD是不可分辨的,对于保守的TGDs来说是不可分辨的,即使T1是空的,对于保守的TGDs也是不可分辨的,对于前沿的TGDs来说也是不可分辨的。
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