Find Base-Processes using BPM APIs ProcessInstanceFilterCriteria

Hi,

using the BPM API I search all Processes with a user-defined Status and this works well.

But in this results, there are all processes (no matter base or sub process) on the samel level.

Is there a SAP-Solution to search ONLY Base Processes?

Currently, I iterate over all processes. Then I delete every process with "parentProcessId = null"

Now, in ProcessInstanceFilterCriteria is the Parent_Process_Instance_ID, but there you can only search for a specific ID. I set it to null or set it to blank, an exception ist thrown, the queryCriteria could not be interpreted..

Thanks in advance for your answers.