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The execution of a particular activity or process is restricted by a schedule. This schedule provides restrictions on when the respective element may be executed, i.e., the schedule defines time slots in which the respective activity may be started or completed. Usually, the structure of the schedule is known at build-time, while the concrete date is set during run-time (i.e., at the process instance level). Schedules may contain exceptions (e.g., every year except leap years).

A schedule is attached to the respective activity or process.

A schedule restriction can be realized using a timer which is started at process instantiation time and expires at the first endpoint of one of the respective time slots (i.e., when entering or leaving a valid time frame of the particular schedule). The timer is then reset and its expiration date is set to the next endpoint of one of the time slots. This is repeated until the respective activity (process) has been started / completed (cf. Design Choice F) or no more valid time slots are available according to the schedule. Outside of a valid time slot the start of the respective activity (process) should be prevented by the system. If the completion of the respective activity (process) does not occur within a valid time slot or there is no longer a valid time slot available according to the schedule, exception handling is required.