  We address the problem of belief change in (nonmonotonic) logic programming
under answer set semantics. Unlike previous approaches to belief change in
logic programming, our formal techniques are analogous to those of
distance-based belief revision in propositional logic. In developing our
results, we build upon the model theory of logic programs furnished by SE
models. Since SE models provide a formal, monotonic characterisation of logic
programs, we can adapt techniques from the area of belief revision to belief
change in logic programs. We introduce methods for revising and merging logic
programs, respectively. For the former, we study both subset-based revision as
well as cardinality-based revision, and we show that they satisfy the majority
of the AGM postulates for revision. For merging, we consider operators
following arbitration merging and IC merging, respectively. We also present
encodings for computing the revision as well as the merging of logic programs
within the same logic programming framework, giving rise to a direct
implementation of our approach in terms of off-the-shelf answer set solvers.
These encodings reflect in turn the fact that our change operators do not
increase the complexity of the base formalism.
