Prior to SAP NetWeaver 7.0, the central object for the transformation was the InfoSource. The central fields of the DataSource are assigned to the corresponding InfoObjects here. The data can also be transformed using transfer rules. Update rules are then used to specify how the data (key figures, time characteristics, characteristics) is updated to InfoProviders from the communication structure of an InfoSource.
You can still use this concept, although we actually recommend switching to the new transformation concept as of SAP NetWeaver 7.0.
You can find the documentation about the update rules at .
You can find the documentation for InfoSource 3.x at .