In a task definition, you can specify one or more deadlines by which a task must be started and also one or more deadlines by which a task must be completed. If a particular start date or completion date is missed, you can trigger a particular action to occur.
There are several actions that are available, as described in
About Task Deadlines and Escalations
In addition, you can create and deploy a BPEL process to provide your own custom action.
To Create the Custom Notification Process:
File > New > Bpel Process
Name the file and click next.
In the BPEL templates page, select Custom B4P Notification.
A process is started for you, with the receive already implemented. You can add the programming logic you wish.
The interface that is implemented is:
<input message="aeb4pnw:processCustomNotificationRequest" />
Adding the Service to the Start or Completion Deadline Property:
Once you have created and deployed your BPEL process, you can select process invocation, as described in
Invoking a Process When a Task Deadline Occurs