A search facility is used to predict the impact of change on events detected in application logic, where the change may involve a computing resource used by or referenced by the application logic andor by event detection logic. Several user profiles are provided from which a user may be associated. The task network represents the relationships between the tasks of the first process. The second upright portion is biased towards and yieldingly interlocks with the channel. The invention thereby provides a timing generation circuit which can contribute to miniaturization and reduction of the cost of the set and a display apparatus of the active matrix type in which the timing generation circuit is incorporated.