Updates in disjunctive deductive databases : a minimal model based approach

The issue of updates in Disjunctive Deductive Databases DDDBs under the minimal model semantics is addressed. We consider ground clause addition and deletion in a DDDB. The approach of this paper is based on manipulating the clauses of the theory to produce the required change to the minimal model structure necessary to achieve the clause addition/deletion update. First we deal with ground positive clause updates in ground DDDBs. Later we consider positive then general clause addition deletion in the class of range restricted DDDBs. When we give more than one algorithm for a case we comment on the comparative merits and limitations of each. We use the freedom offered by the multiple possibilities for achieving an update to select the one with the least change to the minimal model structure of the theory. We argue that such minimality is desirable if one interprets the minimal model structure as representing the possible states of the modeled world and therefore an update must act them minimally