1) IDL (interface definition language) is a generic term for a language that lets a program or object written in one language communicate with another program written in an unknown language. In distributed object technology, it's important that new objects be able to be sent to any platform environment and discover how to run in that environment. An Object Request Broker ( ORB ) is an example of a program that would use an interface definition language to "broker" communication between one object program and another one.
An interface definition language works by requiring that a program's interfaces be described in a stub or slight extension of the program that is compiled into it. The stubs in each program are used by a broker program to allow them to communicate.
2) IDL (Interactive Data Language) is a language for creating visualizations based on scientific or other data.
3) IDL (interactive distance learning) is a general term for learning that takes place through remote telecommunication and that allows students to participate from a distance. Television has been used for many years for non-interactive distance learning. Teleconference classes are becoming more common where higher bandwidth and such technologies as ISDN and satellite communication permit. The World Wide Web, with or without multimedia, offers new possibilities.