Representing Actions over Dynamic Domains

Abstract

Current action theories are usually based on static domains in the sense that objects in the domain are fixed and actions only change properties or relationships related to these objects, but cannot create new objects or destroy current objects in the domain. In this paper, we propose a new action language called $\mathcal{D}$ which handles dynamic domains. In the context of $\mathcal{D}$ actions may not only have normal effects as in other action theories, but also have effects of creating or destroying things in the domain. $\mathcal{D}$ has a similar syntax of $\mathcal{A}$ family languages but with a different model theoretic semantics in which a term is allowed to be undefined in the domain at some states. We also investigate the semantic properties of $\mathcal{D}$ in detail and illustrate how our approach overcomes the difficulty in representing actions over dynamic domains.