Action language ℬℭ+

Joseph Babb, Joohyung Lee

Abstract: Action languages are formal models of parts of natural language that are designed to describe effects of actions. Many of these languages can be viewed as high-level notations of answer set programs structured to represent transition systems. However, the form of answer set programs considered in the earlier work is quite limited in comparison with the modern Answer Set Programming (ASP) language, which allows several useful constructs for knowledge representation, such as choice rules, aggregates and abstract constraint atoms. We propose a new action language called B C +, which closes the gap between action languages and the modern ASP language. The main idea is to define the semantics of B C + in terms of general stable model semantics for propositional formulas, under which many modern ASP language constructs can be identified with shorthands for propositional formulas. Language B C  + turns out to be sufficiently expressive to encompass the best features of other action languages, such as languages B , C , C + and B C . Computational methods available in ASP solvers are readily applicable to compute B C +, which led to an implementation of the language by extending system cplus2asp .