atalog: A logic language for expressing search and optimization problems

Abstract

This paper presents a logic language for expressing NP search and optimization problems. Specifically, first a language obtained by extending (positive) DATALOG with intuitive and efficient constructs (namely, stratified negation, constraints, and exclusive disjunction) is introduced. Next, a further restricted language only using a restricted form of disjunction to define (nondeterministically) subsets (or partitions) of relations is investigated. This language, called NP Datalog, captures the power of DATALOG ¬ in expressing search and optimization problems. A system prototype implementing NP Datalog is presented. The system translates NP Datalog queries into Optimization Programming Language (OPL) programs which are executed by the ILOG OPL Development Studio. Our proposal combines easy formulation of problems, expressed by means of a declarative logic language, with the efficiency of the ILOG System. Several experiments show the effectiveness of this approach.

Incorporating Stratified Negation into Query-Subquery Nets for Evaluating Queries to Stratified Deductive Databases

“…These two semantics coincide for certain classes of logic programs [35,16,21], including stratified logic programs and stratified Datalog ¬ programs. The stable model semantics is used for answer set programming (ASP), and systems like DLV [27], NP Datalog [22] and clasp [17], which deal among others with ASP, can be used for answering queries to stratified Datalog ¬ databases. However, as the main aim of ASP engines is to find an answer set (i.e., a stable model) for a given logic program, they are not goal-driven and, in general, not as efficient as expected for answering queries to stratified Datalog ¬ databases.…”