A language for default reasoning about actions

Action languages allow for a concise representation of actions and their effects while at the same time being easily readable and writable for humans. In this paper, we introduce D, the first action language that centres around default reasoning about actions and change. It allows to specify normal Reiter-style defaults and provides a semantics that has at its core the groundedness of conclusions. This is not only of use for default conclusions, but also for D's solution to the ramification problem. Additionally, our language does not suffer from Yale Shooting-like counterexamples since it uses different mechanisms for default persistence and default change. The answer set programming paradigm is used as the basis of D's implementation, which we prove sound and complete with respect to the language's semantics. We finally present a showcase application for the language: its straightforward solution to the qualification problem.