Existential rules form an expressive Datalog-based language to specify ontological knowledge. The presence of existential quantification in rule-heads, however, makes the main reasoning tasks undecidable. To overcome this limitation, in the last two decades, a number of classes of existential rules guaranteeing the decidability of query answering have been proposed. Unfortunately, only some of these classes fully encompass Datalog and, often, this comes at the price of higher computational complexity. Moreover, expressive classes are typically unable to exploit tools developed for classes exhibiting lower expressiveness. To mitigate these shortcomings, this paper introduces a novel general syntactic condition that allows us to define, systematically and in a uniform way, from any decidable class $\mathcal{C}$ of existential rules, a new class called Dyadic-$\mathcal{C}$ enjoying the following properties: $(i)$ it is decidable; $(ii)$ it generalises Datalog; $(iii)$ it generalises $\mathcal{C}$; $(iv)$ it can effectively exploit any reasoner for query answering over $\mathcal{C}$; and $(v)$ its computational complexity does not exceed the highest between the one of $\mathcal{C}$ and the one of Datalog. Under consideration in Theory and Practice of Logic Programming (TPLP).

翻译：存在规则是一种基于Datalog的表达性语言，用于指定本体知识。然而，规则头部存在量化的存在使得主要推理任务不可判定。为克服这一限制，过去二十年间，研究者提出了多类保证查询回答可判定的存在规则。遗憾的是，其中仅有一部分能完全涵盖Datalog，且这通常以更高的计算复杂度为代价。此外，表达性强的类别往往无法利用为表达性较弱的类别所开发的工具。为缓解这些问题，本文提出一种新颖的通用句法条件，使得我们可以系统且统一地从任何可判定类$\mathcal{C}$的存在规则中定义一个新类——Dyadic-$\mathcal{C}$。该类具备以下性质：(i) 可判定；(ii) 泛化Datalog；(iii) 泛化$\mathcal{C}$；(iv) 能有效利用任何针对$\mathcal{C}$进行查询回答的推理器；(v) 其计算复杂度不超过$\mathcal{C}$与Datalog中较高者。本文正在考虑发表于《逻辑编程理论与实践》（TPLP）。