Causal Laws and Multi-Valued Fluents
This work addresses a specific inconvenience in nonmonotonic formalisms for AI researchers, representing an incremental extension to improve elaboration tolerance.
The paper tackles the limitation of existing action languages that only support truth-valued fluents by extending causal logic and language C to allow multi-valued fluents from arbitrary sets, resulting in a new language C+ that enables action description via attributes and connects to related formalisms like ADL.
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.