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Fig. 5.8 Required exception interface

to determine if an exception has occurred. Also, certain tasks may have associated
deadlines that have passed, a task being performed by an application or process may
fail, or an exception may be raised externally. With all of these events, the context of
the current instance is important in determining the appropriate action to take. That
action may include suspending, canceling, restarting, or completing a task and/or
case instance, as well as performing some compensatory activities. Often a series of
such actions will be needed to successfully handle an exception. Also, action may
need to be taken at the task level, the case instance level, or may even affect all of
the current case instances for a specification.
In the Worklet Service, all of the necessary actions are captured in an exception-
handling process (exlet). As mentioned previously, an exlet may contain a series
of steps incorporating the actions described earlier, and may include one or more
worklets to perform compensatory activities as part of an exception-handling
process.