The transition to using Cognos with HR and Financial data will occur over time. An assessment of the current SAP Business Warehouse (BW) environment needs to occur first along with any resulting build out or rebuild of the BW.
In the mean time, reporting against the SAP BW occurs using Business Explorer (BEx).
Business Warehouse
Business Explorer (BEx)
Reporting against legacy data (pre-SAP) occurs with the data residing in the Decision Support System (DSS) using Brio.
DSS (Decision Support System)
Brio