We consider an extended definition of well-typed programs to general logic programs, i.e., logic programs with negated literals in the body of the clauses. This is a quite large class of programs which properly includes all the well-moded ones. We study termination properties of well-typed general logic programs while employing the Prolog's left-to-right selection rule. We introduce the notion of typed acceptable program and provide an algebraic characterization for the class of well-typed programs which terminate on all well-typed queries.

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.

Recent logic programming languages employ dynamic scheduling of calls to improve efficiency of programs. Dynamic scheduling is realized by allowing some calls to be dynamically "delayed" until their arguments are sufficiently instantiated. To this end, logic languages are extended with constructs such as delay declarations. However, many declarative properties that hold for logic and pure Prolog programs do not apply any longer in this extended setting. In particular, the equivalence between the model-theoretic and operational semantics does not hold. In this paper, we study the class of input-consuming programs. Firstly, we argue that input-consuming logic programs are suitable for modeling programs employing delay declarations. Secondly, we show that -- under some syntactic restrictions -- the S-semantics of a program is correct and fully abstract also for input-consuming programs. This allows us to conclude that for a large class of programs employing delay declarations there ...

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