How to take action or trigger a process based on Task state change

@tobil To the best of my knowledge, there isn't a clear solution for this. It might be relatively easier to write assigned status(trigger a sub-process as soon as the user input task is hit) and completed status(post completion of the task).

But the statuses such as Reassign, Accept, Reject, Return Task to actual assignees etc are hard to capture until you depend on a process that makes use of a timer to query the task status frequently and I believe this kind of mechanism is really expensive. The problem here is, Appian hasn't yet provided the capability to capture the Reassign, Accept, Reject, Return events that we perform on a Task.

One option you might think of is, having all the functionalities such as Reassign, Accept etc on the form but it may not be a great idea to override or ignore the OOTB functionalities extend this kind of functionalities to each and every task. Have you had a look at 'Task Metric Utilities' plugin at http://bit.ly/2cY6mgB? If not, try to do so. It doesn't fit your requirement for sure but might give you a kick start in case if you think of a batch process. (Difference is that the plugin is designed to run on nightly basis afaik whereas the one which you want should actually run a process which will constantly monitor the status of Task)

The other option you might need to think of is to visit the API and see what it offers to you in order to retrieve the desired information.

Finally, I would also suggest giving thoughts over the value addition to Business in doing so. Maybe if you can elaborate the business use case, the practitioners here might come up with some alternate solutions.

@tobil To the best of my knowledge, there isn't a clear solution for this. It might be relatively easier to write assigned status(trigger a sub-process as soon as the user input task is hit) and completed status(post completion of the task).

But the statuses such as Reassign, Accept, Reject, Return Task to actual assignees etc are hard to capture until you depend on a process that makes use of a timer to query the task status frequently and I believe this kind of mechanism is really expensive. The problem here is, Appian hasn't yet provided the capability to capture the Reassign, Accept, Reject, Return events that we perform on a Task.

One option you might think of is, having all the functionalities such as Reassign, Accept etc on the form but it may not be a great idea to override or ignore the OOTB functionalities extend this kind of functionalities to each and every task. Have you had a look at 'Task Metric Utilities' plugin at http://bit.ly/2cY6mgB? If not, try to do so. It doesn't fit your requirement for sure but might give you a kick start in case if you think of a batch process. (Difference is that the plugin is designed to run on nightly basis afaik whereas the one which you want should actually run a process which will constantly monitor the status of Task)

The other option you might need to think of is to visit the API and see what it offers to you in order to retrieve the desired information.

Finally, I would also suggest giving thoughts over the value addition to Business in doing so. Maybe if you can elaborate the business use case, the practitioners here might come up with some alternate solutions.