Datalog+/-: questions and answers

Datalog+/- is a conceptually very simple formalism that extends plain Datalog with features such as existential quantifiers, equalities, and the falsum in rule heads and, at the same time, restricts the rule syntax so as to achieve decidability and, when required, tractability. Datalog+/- provides a uniform framework for query answering and reasoning with incomplete data. It generalizes disparate other KR formalisms such as plain Datalog, description logics (DLs), in particular, DL-Lite and EL, F-Logic Lite, highly relevant fragments of UML class diagrams, data-exchange formalisms, graph query languages such as SPARQL, and so on. The goal of this paper is to give concise answers to frequently asked questions about Datalog+/-.