A motion closed world asumption

  • Authors:

  • Fusun Yaman;Dana Nau;V. S. Subrahmanian

  • Affiliations:

  • Department of Computer Science, University of Maryland Institute for Advanced Computer Studies, Institute for Systems Research, University of Maryland, College Park, MD;Department of Computer Science, University of Maryland Institute for Advanced Computer Studies, Institute for Systems Research, University of Maryland, College Park, MD;Department of Computer Science, University of Maryland Institute for Advanced Computer Studies, Institute for Systems Research, University of Maryland, College Park, MD

  • Venue:
  • IJCAI'05 Proceedings of the 19th international joint conference on Artificial intelligence
  • Year:
  • 2005

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Abstract

Yaman et. al. [Yaman et al., 2004] introduce "go theories" to reason about moving objects. In this paper, we show that this logic often does not allow us to infer that an object is not present at a given place or region, even though common sense would dictate that this is a reasonable inference to make. We define a class of models of go-theories called coherent models. We use this concept to define a motion closed world assumption (MCWA) and develop a notion of MCWA-entailment. We show that checking if a go-theory has a coherent model is NP-complete. An in atom checks if a given object is present in a given region sometime in a given time interval. We provide sound and complete algorithms to check if a ground in literal (positive or negative in atom) can be inferred from a go-theory using the MCWA. In our experiments our algorithms answer such queries in less than 1 second when there are up to 1,000 go-atoms per object.