Interface A shared boundary between various systems or programs. An interface is also the equipment or device that makes it possible to interoperate two systems. From : www.nps.gov/gis/gps/glossary.htm A shared boundary across which information is passed. [IEEE 91] An abstraction of the behavior of an object obtained by hiding observable actions of that object outside a specified subset. [open distributed processing (ODP)]. From : www.sei.cmu.edu/opensystems/glossary.html