12.4. Task Lifecycle

A human task is created when a user task node is encountered during the execution. The process leaves the user task node only when the associated human task is completed or aborted. The human task itself has a complete life cycle as well. The following diagram describes the human task life cycle.
Diagram from the WS-HumanTask specification

Figure 12.1. Human Task Life Cycle

A newly created task starts in the Created stage. It then automatically comes into the Ready stage. The task then shows up on the task list of all the actors that are allowed to execute the task. The task stays in the Ready stage until one of these actors claims the task. When a user then eventually claims the task, the status changes to Reserved. Note that a task that only has one potential (specific) actor is automatically assigned to that actor upon creation of the task. When the user who has claimed the task starts executing it, the task status changes from Reserved to InProgress.
Once the user has performed and completed the task, the task status changes to Completed. In this step, the user can optionally specify the result data related to the task. If the task could not be completed, the user may indicate this by using a fault response, possibly including fault data, in which case the status changes to Failed.
While this life cycle explained above is the normal life cycle, the specification also describes a number of other life cycle methods, including:
  • Delegating or forwarding a task, so that the task is assigned to another actor.
  • Revoking a task, so that it is no longer claimed by one specific actor but is (re)available to all actors allowed to take it.
  • Temporarily suspending and resuming a task.
  • Stopping a task in progress.
  • Skipping a task (if the task has been marked as skippable), in which case the task will not be executed.