Many Historians will collection information from internal nodes or from some underlying system. The collected information might be obtained using non-OPC UA communication. This type of historical configuration is vendor specific.

Some Historians might collected information from other OPC UA Servers. The Historian might mirror the point in their own information models and use the HasCurrentData or the HasCurrentEvent Reference to indicate the source node for the data or Event. Mirroring Variables is typically simple. Variables usually do not have complex structure or nested Variables under them. For Events, the source of Events might be the Server Node or some higher level Object and replicating that Object or entire Server and the complex structure under it would not make sense.