Finite Model Reasoning in Hybrid Classes of Existential Rules

Two paradigmatic restrictions that have been studied for ensuring the decidability of query answering under existential rules are guardedness and stickiness. With the aim of consolidating these restrictions, a flexible condition, called tameness, has been proposed a few years ago, which relies on hybrid reasoning, i.e., a combination of forward and backward procedures. The complexity of query answering under this hybrid class of existential rules is by now well-understood. However, the complexity of finite query answering, i.e., query answering under finite models, has remained an open problem. Closing this problem is the main goal of this work.