Properties of Input-Consuming Derivations

We study the properties of input-consuming derivations of moded logic programs. Input-consuming derivations do not employ a fixed selection rule, and can be used to model the behavior of logic programs using dynamic scheduling and employing constructs such as delay declarations. We consider the class of nicely-moded programs and queries. We show that for these programs one part of the well-known Switching Lemma holds also for input-consuming derivations. Furthermore, we provide conditions which guarantee that all input-consuming derivations starting in a Nicely-Moded query are finite. The method presented here is easy to apply and generalizes other related works.