Transformations between signed and classical clause logic

In the last years two automated reasoning techniques for clause normal form arose in which the use of labels are prominently featured: signed logic and annotated logic programming, which can be embedded into the first. The underlying basic idea is to generalise the classical notion of a literal by adorning an atomic formula with a sign or label which in general consists of a possibly ordered set of truth values. In this paper we relate signed logic and classical logic more closely than before by defining two new transformations between them. As a byproduct we obtain a number of new complexity results and proof procedures for signed logics.