An intelligent interface cannot just respond passively to its user's commands and queries. It must be ableto take the initiative in order to volunteer information, correct user misconceptions, or reject unethical userrequests. To do these things, a system must be an intelligent agent. UCEgo is the intelligent agent componentof UC (UNIX Consultant), a natural-language system that helps the user solve problems in using the UNIXoperating system. UCEgo provides UC with its own goals and plans....