When you add the a:a tag to a device or point in a Supervisor station, that device or point becomes an ancestor to similar points in remote stations. You can use these ancestors to find certain tags, such as hs:zoneAirTempSensor and potentially aggregate or access the information from the remote station.

Hierarchies group tags hierarchically. Any device or point to which you assign a tag as part of a hierarchy can serve as an ancestor tag.