While the intention rules describe a distribution over starting intentions, a utility function gives a value to each plan. It should be used to evaluate the different outcomes at the leaves of the game tree, producing a number, which is then used to compare different alternatives in the game tree. In section 2.13 it was stated that in planned dialogue, a compositional evaluation function is required that can be used on every element of the plan search space. Here, the two most important evaluation measures are taken, task completion and execution time, although others such as speech recognition error and response time are also compositional and can be used in the same way. Since evaluation is compositional, a recursive search of the plan structure is required that adds up all of the utility contributions of the acts in the plan. For task completion, the presence of the goal node in the complete plan is an indication of success, for which a positive utility is gained. Therefore the designer specifies a reward and goal node for the system. Each dialogue act is assumed to have some constant cost in terms of execution time. Therefore, the designer needs to specify this number for each of the terminals that appear in its plan rules. The system should search the plan structure automatically, using those given numbers. Finally, a weighted sum should be used, as in the PARADISE framework, to obtain an overall utility for the dialogue.