Layered Models Top-Down Querying of Normal Logic Programs

Abstract. For practical applications, the use of top-down query-driven proofprocedures is essential for an efficient use and computation of answers using Logic Programs as knowledge bases. Additionally, abductive reasoning on demand is intrinsically a top-down search method. A query-solving engine is thus highly desirable. The current standard 2-valued semantics for Normal Logic Programs (NLPs), the Stable Models (SMs) semantics, does not allow for top-down query-solving because it does not enjoy the relevance property -- and moreover, it does not guarantee the existence of a model for every NLP. To overcome these current limitations we introduce here a new 2-valued semantics for NLPs -- the Layered Models semantics -- which conservatively extends the SMs, enjoys relevance and guarantees model existence among other useful properties. Moreover, for existential query answering there is no need to compute total models, but just the partial models that sustain the answer to the query, or o...

• Type: Conference
• Year: 2009
• Where: PADL
• Authors: Alexandre Miguel Pinto, Luís Moniz Pereira
• Keywords: Layered Models Semantics, PADL 2009, Programming Languages, Standard 2-valued Semantics, Top-down Search Method