An interface description language or interface definition language (IDL) 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. IDLs are usually used to describe data types and interfaces in a language-independent way, for example, between those written in C++ and those written in Java.
IDLs are commonly used in remote procedure call software. In these cases the machines at either end of the link may be using different operating systems and computer languages. IDLs offer a bridge between the two different systems.
Software systems based on IDLs include Sun's ONC RPC, The Open Group's Distributed Computing Environment, IBM's System Object Model, the Object Management Group's CORBA (which implements OMG IDL, an IDL based on DCE/RPC) and Data Distribution Service, Mozilla's XPCOM, Microsoft's Microsoft RPC (which evolved into COM and DCOM), Facebook's Thrift and WSDL for Web services.
Serialization format from Google supporting zero-copy deserialization