Unfold/fold transformations of CCP programs

We introduce a transformation system for concurrent constraint programming (CCP). We define suitable applicability conditions for the transformations which guarantee that the input/output ccp semantics is preserved also when distinguishing deadlocked computations from successful ones. The systems allows to optimize CCP programs while preserving their intended meaning. Furthermore, since it preserves the deadlock behaviour of programs, it can be used for proving deadlock freeness of a class of queries in a given program