On Continual Planning with Runtime Variables

This article discusses the problem of planning and acting in partially observable environments. In many such domains conditional planning for all contingencies is prohibitively hard. Therefore we advocate a continual planning approach, where decisions can, by means of so-called \emphassertions, be deferred until execution time when more information is available. Additionally, we formalize the notion of \emphruntime variables as functional fluents, which can act as placeholders for sensing results unknown at planning time. Using runtime variables and assertions we show how a \emphseries of sequential plans can solve planning tasks that in non-continual planning would necessitate plans with conditional branching and loops.