First Union National Bank, one of the largest banks in the U.S., is in the process of reengineering many of its applications using Java and XML. Like most large companies, its environment is heterogeneous, with OS/390, AIX, Solaris, HP/9000, and Windows NT servers and Windows NT, Windows 98, Solaris, and AIX clients. Given this environment, First Union chose Java for platform-independent code and XML for platform-independent data.