On temporal, nonmonotonic, nondeterministic logic databases

We consider in this paper an extension of Datalog with mechanisms for temporal1 nonmonotonic and nondeterministic reasoning, which we refer to as Datalog++. We show, by means of examples, its fiexibility in expressing queries concerning aggregates and data cube. Also, we show how iterateci fìxpoint and stable model semantics can be combined to the purpose of clarifying the semantics of Datalog++ programs, and supporting their efficient execution. Finally, we provide a more concrete implementation strategy, on which basis the design of optimization techniques tailored for Datalog++ is addressed.