A lot of extract-transform-load (ETL) work requires unloading and un-transforming first. Rather than \(ETL\), it’s \(L_A^{-1}T_A^{-1}ET_BL_B\). What the data provider did is \(A\). What you want to do is \(B\). The data provider gave you a “dump” of their data. You don’t know what it means. If you did, you could extract (subset) from it according to your needs – filter entities by some meaningful criteria and collect selected attributes.