Alternative Historical Data

Hello

Could you help me with this question?

I'm trying to import alternative historical data to SAP-C. I found documentation in

At some point, it is said:

"In principle, alternative historical data can come from any data source.

· In SAP R/3, a technical link to the component SAP BW is provided as standard, which you can use to load alternative historical data into SAP R/3.

· You can link to any other data source using the Business Add-Ins (BAdI) provided."

This alternative data source, what does it refer to? Can it be another SAP componente (besides BW) or a different data source such as a .xls?

Thank you