IRIS is an extensible reasoning engine for Datalog extended with function symbols, unsafe rules, negation, locally stratified or non-stratified programs, XML schema data types and a comprehensive and extensible set of built-in predicates.
Elly is a reasoner for entailment and satisfiability checking of ELP knowledge-bases. It is written in java and relies on the IRIS Datalog reasoner (https://sourceforge.net/projects/iris-reasoner) for its implementation.