Side-Change Transformation

Many logical problems, such as proof problems and query-answering problems, can be mapped into modelintersection (MI) problems, which constitute one of the largest and most fundamentally important classes of logical problems. To solve MI problems, many equivalent transformation rules have been employed. In this paper, we introduce a new transformation, called side-change transformation, and propose unfolding/sidechange computation control, i.e., when neither unfolding nor definite-clause removal is applicable, an attempt is made to transform a given problem using side-change transformation so as to derive an equivalent problem to which unfolding is applicable. The correctness of side-change transformation is shown. While a resolutionbased proof method increases problem size monotonically no matter what control is taken, a reduction of problem size can often be achieved by using the unfolding/side-change control.