The DMCS Solver for Distributed Nonmonotonic Multi-Context Systems

The DMCS system is an implementation of the equilibrium semantics for heterogeneous and nonmonotonic multi-context systems (MCS) [3], which feature contexts with heterogeneous and possibly nonmonotonic logics. Each context in an MCS comprises of two parts: a local knowledge base and a set of bridge rules that can access the beliefs of other contexts and add new information to the knowledge base. In this setting, contexts are loosely coupled, and may model distributed information linkage applications; thus it is natural to have a system that allows for the distributed evaluation of MCS. In an MCS M = (C1, . . . , Cn), each context Ci is characterized by a knowledge base kbi and a set of bridge rules bri. In our implementation, each kbi is in DLV syntax as in [6]. The bri are sets of nonmonotonic rules p0 ← (c1 : p1), . . . , (cj : pj),not (cj+1 : pj+1), . . . ,not (cm : pm). where the (ck : pk) are bridge atoms; the index ck refers to a context Cck and pk is a possible belief of Cck ; intuitively, the atom is true if pk is in the belief set of context Cck . If the body evaluates to true with respect to a belief state, which is a sequence S = (S1, . . . , Sn) of belief sets Si of Ci, 1 ≤ i ≤ n, then p0 has to be added to kbi. The semantics of M is then given in terms of stable belief sets (called equilibria). Partial Equilibria are equilibria in a sub-MCS of M induced by a single context Ck resp. a collection Ck1 , . . . , Ckj of contexts.