On Progression and Query Evaluation in First-Order Knowledge Bases with Function Symbols
Vaishak Belle, Gerhard Lakemeyer
In a seminal paper, Lin and Reiter introduced the notion of progression of basic action theories. Unfortunately, progression is second-order in general. Recently, Liu and Lakemeyer improve on earlier results and show that for the local-effect and normal actions case, progression is computable but may lead to an exponential blow-up. Nevertheless, they show that for certain kinds of expressive first-order knowledge bases with disjunctive information, called proper+, it is efficient. However, answering queries about the resulting state is still undecidable. In this paper, we continue this line of research and extend proper+ to include functions. We prove that their progression wrt local-effect, normal actions, and range-restricted theories, is first-order definable and efficiently computable. We then provide a new logically sound and complete decision procedure for certain kinds of queries.