Application Programming Interface - (API) - Maybe known as Core Middleware and typically can be found in middleware. The API is a computerized system or program library that provides support (and thus fulfills) service requests that other computer programs make of it. For instance, the Windows API concerns itself with the interaction between the operating system and applications. The API is a series of functions that programs can use to make the operating system perform specific tasks. APIs can allow for faster development, since programming to a device's API is designed to be easier than programming directly to the device. APIs can also allow programming without having intimate knowledge of the device or software that you're sending commands to. The API can be the underlying technical facility for features such as the Electronic Program Guide, Digital Video Recorders (DVRs) and many Interactive Television services.
https://en.wikipedia.org/wiki/Application_Programming_Interface

Interactive TV Application

Interactive TV Platforms

Middleware