We propose a set of transformation rules for constraint logic programs with negation. We assume that every program is locally strati- ed and, thus, it has a unique perfect model. We give sucient conditions which ensure that the proposed set of transformation rules preserves the perfect model of the programs. Our rules extend in some respects the rules for logic programs and constraint logic programs already considered in the literature and, in particular, they include a rule for unfolding a clause with respect to a negative literal.

In questo articolo presentiamo brevemente la metodologia di trasformazione dei programmi per lo sviluppo di software corretto ed efficiente. Ci riferiremo, in particolare, al caso della trasformazione e dello sviluppo dei programmi logici con vincoli. In this paper we briefly describe the use of the program transformation methodology for the development of correct and efficient programs. We will consider, in particular, the case of the transformation and the development of constraint logic programs.