How Can We Observe and Describe Chaos?
  We propose a new approach to define chaos in dynamical systems from the point of view of Information Dynamics. Observation of chaos in reality depends upon how to observe it, for instance, how to take the scale in space and time. Therefore it is natural to abandon taking several mathematical limiting procedures. We take account of them, and chaos degree previously introduced is redefined in this paper. 
Andrzej Kossakowski, Masanori Ohya and Yosio Togawa