What an agent takes an instruction to mean must be able to evolve as the agent acts. All that is required is that he be able to establish a referent once he gets to the kitchen. The understanding process must be able to allow for this delay. When an agent is told Vacuum against the direction of the pile to leave it raised , the agent can find out through vacuuming what direction of sweep leaves the carpet pile raised. Again, he does not need to know the referent before starting to act, but he must be able to use the instruction to guide what it is he needs to know.
Animation follows from model-based simulation.
Different spatial environments can easily be constructed and modified, to enable designers to vary the situations in which the figures are acting. While the environment through which a Jack agent moves influences its low-level responses, we have found that a great many behavioral constraints can be derived through instruction understanding and planning. Further descriptions of work being done in the context of AnimNL can be found in CLiFF Note entries for Geib , Levison , Moore , Webber and White . References N. Badler, C. Phillips, and B. Webber. Oxford University Press, 1993.