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5 Exception Handling 149
By describing these factors in detail for a given exception, it is possible to pre-
cisely describe a strategy to handle it with, both in terms of dealing with the affected
work item and also more generally in terms of mitigating its overall effects. Each of
the possible configurations for each of these factors follow.

5.2.1 Exception Types

The first factor that is relevant to how an exception will be handled is the type of
the exception. A comprehensive review of the workflow literature and current com-
mercial offerings indicate that there are five distinct types of exceptional events that
can occur during the execution of a business process that are able to be effectively
remedied. These are as follows:

Work Item Failure (WIF)

Work item failure is characterized by the inability of a currently executing work
item to either continue executing or to progress any further in its current execution
state. This may be a consequence of a variety of distinct causes such as user-initiated
termination of the program that implements the work item; the failure of a hardware,
software, or network resource associated with the work item; or a user indication
that the associated work item should considered as having failed rather than having
completed successfully. Often this form of failure cannot easily be dealt with within
the context of a process model or the effects of such failure are not localized to
a specific part of the process and an exception-based handling strategy offers an
effective means of managing the situation such that both later work items and the
process as a whole continue to behave correctly.

Deadline Expiry (DEX)

The use of deadlines within business processes are a common means of enforc-
ing organizational performance requirements within a business process. Generally,
they are associated with a specific work item and indicate when it should be com-
pleted, although commencement deadlines are also possible. Often when specifying
a deadline, it is also useful to define the action that will be pursued if the deadline is
reached and the work item has not been started or completed.

Resource Unavailability (RUN)
It is often the case that a work item requires access to one or more resources during
its execution. These may be data resources that contain information required for the