Interruptible Activity Region   An interruptible activity region is a type of activity group which provides a mechanism for destroying all tokens and terminating all behaviors in the section of the activity enclosed within the boundary of the region. An interruptible activity region can contain any number of nodes and flows. When a token is accepted by a special kind of edge called an interrupting flow (edge), which is designated by a lightning bolt, it leaves the region and all other tokens are destroyed and behaviors within the region are terminated.

Explanation

When an activity has been invoked situations often arise where one or more actions contained in the activity need to be terminated under certain conditions. An interruptible activity region allows a number of nodes and flows to be grouped together inside a dashed boundary and may have an interrupting flow along which tokens travel when a particular event, behavior or event occurs. Once the interrupting flow receives the token all tokens and behaviors inside the region are terminated. Any tokens still within the region but destined to pass to nodes outside the region are allowed to flow out (including the one that resulted in the interruption). In our daily lives there are examples of this type of mechanism. When we purchase an airline ticket over the internet we typically have to select travel dates, flight times, provide information about the passenger(s), such as name and contact number and then our credit card payment details. The flight selection and passenger details sections of the forms could all be contained in an interruptible activity region since a customer could easily cancel the request during this part of the process. Once the credit card details have been entered and the payment button has been pressed the request cannot typically be interrupted. These latter processes would lie outside the region.

Related Entries

Exception Handler  Used Together An exception handler is related to an interruptible activity region in that both elements model how unusual or out of the ordinary events are handled. They both use a lightning bolt style flow as a conduit for the tokens. Both specify an alternate behavior when an event occurs that is exceptional or interrupts the main flow in the activity.