We explore phase transitions of plan modification, which mainly focus on the conformant planning problems. By analyzing features of plan modification in conformant planning problems, quantitative results are obtained. If the number of operators is less than, almost all conformant planning problems can't be solved with plan modification. If the number of operators is more than, almost all conformant planning problems can be solved with plan modification. The results of the experiments also show that there exists an experimental threshold of density (ratio of number of operators to number of propositions), which separates the region where almost all conformant planning problems can't be solved with plan modification from the region where almost all conformant planning problems can be solved with plan modification.

This agent receives on-the-fiy requests from other (human) agents for tasks such as: bring copies of paper to David today, bring a book to George this afternoon, or warn Ronny immediately that a meeting is postponed. Each task requires a sequence of actions, such as: go to the location of the paper, get the paper, take the paper to the copy room, etc. The agent must plan its actions in real time in order to react effectively to the incoming stream of requested tasks.