MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 2: An Introduction to SQL and ODBC
A standard data stream protocol is one way to access data in heterogeneous DBMSs. In fact, standard data stream protocols already exist: the proposed ANSI/ISO Relational Data Access (RDA) standard and the IBM Distributed Relational Database Architecture (DRDA). Although both systems show promise, neither is widely implemented today.