Editing X-machine (section)

== 1980s ==
Interest in the X-machine was revived in the late 1980s by Mike Holcombe,<ref
  name="Hol88a">M. Holcombe (1988)
  'X-machines as a basis for dynamic system specification',
  ''Software Engineering Journal'' '''3'''(2), pp. 69-76.</ref> who noticed that the model was ideal for software [[formal specification]] purposes, because it cleanly separates ''control flow'' from ''processing''. Provided one works at a sufficiently abstract level, the control flows in a computation can usually be represented as a finite-state machine, so to complete the X-machine specification all that remains is to specify the processing associated with each of the machine's transitions. The structural simplicity of the model makes it extremely flexible; other early illustrations of the idea included Holcombe's specification of human-computer interfaces,<ref
  name="Hol88b">M. Holcombe (1988)
  'Formal methods in the specification of the human-machine interface', 
  ''International J. Command and Control, Communications and Info. Systems.'' '''2''', pp. 24-34.</ref>
his modelling of processes in cell biochemistry,<ref
  name="Hol86">M. Holcombe (1986)
  'Mathematical models of cell biochemistry'. 
  Technical Report CS-86-4, Dept of Computer Science, Sheffield University.</ref>
and Stannett's modelling of decision-making in military command systems.<ref
  name="Sta87">M. Stannett (1987) 
  'An organisational approach to decision-making in command systems.' 
  ''International J. Command and Control, Communications and Info. Systems.'' '''1''', pp. 23-34.</ref>