Coherent Integration of Databases by Abductive Logic Programming

We introduce an abductive method for a coherent integration of independent data-sources. The idea is to compute a list of data-facts that should be inserted to the amalgamated database or retracted from it in order to restore its consistency. This method is implemented by an abductive solver, called Asystem, that applies SLDNFA-resolution on a meta-theory that relates different, possibly contradicting, input databases. We also give a pure model-theoretic analysis of the possible ways to `recover' consistent data from an inconsistent database in terms of those models of the database that exhibit as minimal inconsistent information as reasonably possible. This allows us to characterize the `recovered databases' in terms of the `preferred' (i.e., most consistent) models of the theory. The outcome is an abductive-based application that is sound and complete with respect to a corresponding model-based, preferential semantics, and -- to the best of our knowledge -- is more expressive (thus more general) than any other implementation of coherent integration of databases

Compositionality of normal open logic programs

status: publishe

Compositionality of normal open logic programs

status: publishe

Compositionality of Normal Open Logic Programs

Compositionality of programs is an important concern in knowledge representation and software development. In the context of Logic Programming, up till now, the issue has mostly been studied for definite programs only. Here, we study compositionality in the context of normal open logic programming. This is a very expressive logic for knowledge representation of uncertainty and incomplete knowledge on concepts and on problem domain, in which the compositionality issue turns up very naturally. The semantics of the logic is a generalisation (allowing non-Herbrand interpretations) of the well-founded semantics. We provide a number of results which offer different sufficient conditions under which the models of the composition of two theories can be related to the intersection of the models of the composing theories. In particular, under these conditions, logical consequence will be preserved under composition. Keywords : Logic Programming, Knowledge representation. CR Subject Classific..