Sending cache notifications to the backend ABAP

Hi,

1. How the cache notifications are sent to the backend ABAP?

2. What is the role of INTEGRATION_DIRECTORY_HMI ( /dir/CacheRefresh )?

3. If I need to require cache notifications to be sent from PI (ABAP 7.1) to ECC (ABAP 7.0), do i need to have INTEGRATION_DIRECTORY_HMI in ECC?

Thanks and regards,

Sreehari