Causal Laws and Multi-Valued Fluents

TL;DR

This paper extends causal logic and action language C to handle multi-valued fluents, enabling more expressive representations of actions and their attributes, and relates these extensions to existing formalisms like ADL.

Contribution

It introduces C+, an extension of language C that supports multi-valued fluents and attributes, enhancing elaboration tolerance and expressiveness in action representations.

Findings

C+ can be embedded into causal theories with multi-valued constants

Multi-valued constants can be reduced to Boolean constants

C+ relates closely to Pednault's ADL

Abstract

This paper continues the line of work on representing properties of actions in nonmonotonic formalisms that stresses the distinction between being "true" and being "caused", as in the system of causal logic introduced by McCain and Turner and in the action language C proposed by Giunchiglia and Lifschitz. The only fluents directly representable in language C+ are truth-valued fluents, which is often inconvenient. We show that both causal logic and language C can be extended to allow values from arbitrary nonempty sets. Our extension of language C, called C+, also makes it possible to describe actions in terms of their attributes, which is important from the perspective of elaboration tolerance. We describe an embedding of C+ in causal theories with multi-valued constants, relate C+ to Pednault's action language ADL, and show how multi-valued constants can be eliminated in favor of Boolean constants.