Information extraction is the gleaning of needed information from large amounts of data.
We are surrounded with ever-increasing amounts of data that occurs in various forms, including images, text and sound. The challenge of this information overload has pushed emphasis from the generation of new data to the discovery of knowledge taken from diverse and copious data repositories. At its lowest level, an information hierarchy starts with data represented as pixels, waveforms, pulses, and features. It ascends from data to information, developed by combining various forms of data. The hierarchy culminates at the level of knowledge, which conditions information upon the background of experience and likelihood.