How to identify the sub process instance id from REST API

[bhavanikrishnam]

i am trying to run a process model which contains a sub process in it. Once the process instance is created and the flow moves inside the sub process or once the process instance has been completed, i am not able to identify any id being generated for the sub process instance. Rather the tasks inside the sub process are treated as task of the parent process. So please throw some light on how to segregate sub process details from the main process using a REST API call.

[jbarrez]

You can't (at least not in v5), there is no difference in how those two tasks are stored.
So the only way to know is to use the BpmnModel to get the actual ids and check if they are in a subprocess in the process definition.