Two Forms of One Useful Logic: Existential Fixed Point Logic and Liberal Datalog

Andreas Blass Yuri Gurevich Two Forms of One Useful Logic: Existential Fixed Point Logic and Liberal Datalog http://arxiv.org/abs/0811.0977 2008 CoRR abs/0811.0977 db/journals/corr/corr0811.html#abs-0811-0977 informal publication