SAP BW is now called SAP NetWeaver BI and is a part of :
SAP NetWeaver is the open integration and application platform that integrates people, information and processes into one hub, across technologies and organizations, to reduce the total cost of ownership (TCO).
SAP NetWeaver ’04 Master Guide section Technical Scenarios of SAP NetWeaver → SAP Business Information Warehouse → Installation.
SAP Business Warehouse Installation 3.5 - Installation of Components Used for SAP BW