Under the direction of a distinguished Editorial Board, Professor Madan Singh has commissioned over 90 articles which extend, up-date and revise original material from the highly acclaimed Systems & Control Encyclopedia. Particular attention has been paid to newly emerging areas of research and the increasing role of computers has been especially emphasized. Supplementary Volume 1 is the first in a series of biennial Supplements ensuring that the Systems & Control Encyclopedia remains the most comprehensive and up-to-date compendium of systems ideas, methods and applications available.