Information Distance: New Developments
  In pattern recognition, learning, and data mining one obtains information from information-carrying objects. This involves an objective definition of the information in a single object, the information to go from one object to another object in a pair of objects, the information to go from one object to any other object in a multiple of objects, and the shared information between objects. This is called "information distance." We survey a selection of new developments in information distance. 
P. M. B. Vitanyi (National Research Center for Mathematics and   Computer Science in the Netherlands (CWI), Amsterdam)
cs.CV cs.IT math.IT physics.data-an