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State transition diagrams for invocation tasks

Invocation tasks support people when they invoke services. During the lifecycle of an invocation task, certain interactions are possible only in certain task states, and these interactions, in turn, influence the state of the task.

The person who creates and starts the invocation task becomes the task originator. When the task is started, it automatically invokes the service and waits for its result. When the service result is available, the invocation task stores it and the originator can retrieve it as long as the task exists.

The following diagram shows the state transitions that can occur during the lifecycle of invocation tasks:

After creation, the task reaches the inactive state. In this state, you can update task properties, or set custom properties. To invoke the service, the task must be started. It can be started by the originator or one of the potential starters.

After the task starts, it is put into the running state. In this state the task waits for the invoked service to return. The following exceptional events can occur in this state:

The normal task flow is that the service returns with an output or fault message. The task is then put into the finished state if an output message is returned, or the failed state if a fault message is returned. In both cases, the message is available to the task originator and starter.

The failed, terminated, finished, and expired states are end states.

If the task template specifies automatic deletion, the task is either deleted after the deletion timer expires, or it is deleted manually. By default, invocation tasks are not automatically deleted so that the result of the invoked service can be accessed.

A task in one of the end states can be restarted. The task is put back into the running state. Escalations associated with the task are canceled and the deletion timer is also canceled.

Some additional rules apply to inline invocation tasks. These tasks are an integral part of the BPEL process, and thus the process can control their lifecycle:

Lifecycle of human tasks