Date Added: Jul 2009
Modular non-Monotonic Logic Programs (MLPs) under the answer-set semantics have been recently introduced as an ASP formalism in which modules can receive context-dependent input from other modules, while allowing (mutually) recursive module calls. This can be used for more succinct and natural problem representation at the price of an exponential increase of evaluation time. In this paper, the authors aim at an efficient top-down evaluation of MLPs, considering only calls to relevant module instances. To this end, they generalize the well-known Splitting Theorem to the MLP setting and present notions of call stratification, for which they determine sufficient conditions. Call-stratified MLPs allow to split module instantiations into two parts, one for computing input of module calls, and one for evaluating the calls themselves with subsequent computations.