Relational Interface System (RIS) is Intergraph Corporation's middleware for connecting client software and DBMS. Was developed for UNIX (including CLIX) many years before ODBC and last years for Apple Macintosh and Windows computers.
It is used in geographic information systems Modular GIS Environment (MGE) and GeoMedia, the digital photogrammetric station ImageStation, security systems, CAD software (such as MicroStation) and mechanical-design software I/EMS (predecessor of Solid Edge).
References
Relational Interface System Wikipedia(Text) CC BY-SA