Enhancing the expressive power of the U-Datalog language

Elisa Bertino Barbara Catania Roberta Gori Enhancing the expressive power of the U-Datalog language http://arxiv.org/abs/cs.DB/0404003 2004 CoRR cs.DB/0404003 db/journals/corr/corr0404.html#cs-DB-0404003 informal publication