Interval scripts: A programming paradigm for interactive environments and agents

Abstract

In this paper we present interval scripts, a new paradigm for the programming of interactive environments and computer characters. In this paradigm, actions and states of the users and the system computational agents are associated with temporal intervals. Programming is accomplished by establishing temporal relationships as constraints between the intervals. Unlike previous temporal constraint-based programming languages, we employ a strong temporal algebra based in Allen's interval algebra with the ability to express mutually exclusive intervals and to define complex temporal structures. To avoid the typical computational complexity of strong temporal algebras we propose a method, PNF propagation, that projects the network implicit in the program into a simpler, 3-valued (past, now, future) network where constraint propagation can be conservatively approximated in linear time. The interval scripts paradigm is the basis of ISL, or Interval Scripts Language, that was used to build three large-scale, computer-vision-based interactive installations with complex interactive dramatic structures. The success in implementing these projects provides evidence that the interval scripts paradigm is a powerful and expressive programming method for interactive environments. © 2003 Springer-Verlag London Limited.