Relational Theories with Null Values and Non-Herbrand Stable Models
  Generalized relational theories with null values in the sense of Reiter are first-order theories that provide a semantics for relational databases with incomplete information. In this paper we show that any such theory can be turned into an equivalent logic program, so that models of the theory can be generated using computational methods of answer set programming. As a step towards this goal, we develop a general method for calculating stable models under the domain closure assumption but without the unique name assumption. 
Vladimir Lifschitz, Karl Pichotta, and Fangkai Yang
cs.LO cs.AI cs.DB