Question: Changing parent status by child statuses

[TheFellow]

We would like to setup our workflow so that the parent (PBI) items have a Done state which is set deterministically based on the child (Task) states.

Specifically, if all tasks are marked Done, then the PBI is Done. (Examples indicate this is possible)
If a child task is moved back into In Progress, then the PBI moves back to In Progress. (This seems like the same thing, so I don't see why this shouldn't be possible)

My question is this: What happens when all tasks are done (making the PBI Done) and a new task (perhaps already existing) is linked to the PBI. If that other task is not in a Done state then the PBI should be pushed back out to the In Progress state. Similarly, if all but one Task are done, and the unfinished Task is unlinked, will this still trigger the aggregation to be recalculated?

Thanks for your help!

[giuliov]

Work item relationships are computed on the fly, so in the first case should work (PBI go back to In Progress), while in the second case (orphaned Task) nothing should happen.