  This paper describes a system, called PLP, for compiling ordered logic
programs into standard logic programs under the answer set semantics. In an
ordered logic program, rules are named by unique terms, and preferences among
rules are given by a set of dedicated atoms. An ordered logic program is
transformed into a second, regular, extended logic program wherein the
preferences are respected, in that the answer sets obtained in the transformed
theory correspond with the preferred answer sets of the original theory. Since
the result of the translation is an extended logic program, existing logic
programming systems can be used as underlying reasoning engine. In particular,
PLP is conceived as a front-end to the logic programming systems dlv and
smodels.
