I want to build a report which shows who is current assignee of the task and who was previous owner of the task.

Those are all valid points, @sikhivahans, but the smart service Ambrish is referring to allows an external party to reassign a task. For instance, someone goes home sick, so the manager wants to reassign that individual's tasks to someone else.

Other than the smart service, you could use exception flow that is triggered by a variable getting updated via a process-to-process message. It would essentially do the same thing as the smart service, but you would have more control over the process steps prior to the task getting re-assigned.

Those are all valid points, @sikhivahans, but the smart service Ambrish is referring to allows an external party to reassign a task. For instance, someone goes home sick, so the manager wants to reassign that individual's tasks to someone else.

Other than the smart service, you could use exception flow that is triggered by a variable getting updated via a process-to-process message. It would essentially do the same thing as the smart service, but you would have more control over the process steps prior to the task getting re-assigned.