Windows Open Services Architecture. A set of API s for the Windows environment to enable Windows applications to talk to other systems across a network (notably to a mainframe using SNA). WOSA was developed by a consortium of 20 vendors headed by Microsoft. IBM was a member, although initially it rather sniffily said that WOSA won’t be able to do much that you can’t already do from OS/2 anyway. By the mid 1990s, WOSA had created MAPI, SAPI, TAPI, among other standards.