Susan Stepney, Samuel L. Braunstein, John A. Clark, Andy Tyrrell, Andrew Adamatzky, Robert E. Smith, Tom Addis, Colin Johnson, Jonathan Timmis, Peter Welch, Robin Milner, Derek Partridge.
Journeys in Non-Classical Computation I: A Grand Challenge for computing research.

International Journal of Parallel, Emergent and Distributed Systems 20(1):5-19. March 2005


A gateway event is a change to a system that leads to the possibility of huge increases in kinds and levels of complexity. It opens up a whole new kind of phase space to the system’s dynamics. Gateway events during evolution of life on earth include the appearance of eukaryotes (organisms with a cell nucleus), an oxygen atmosphere, multi-cellular organisms, and grass. Gateway events during the development of mathematics include each invention of a new class of numbers (negative, irrational, imaginary, …), and dropping Euclid’s parallel postulate.

A gateway event produces a profound and fundamental change to the system: once through the gateway, life is never the same again. We are currently poised on the threshold of a significant gateway event in computation: that of breaking free from many of our current “classical computational” assumptions. Our Grand Challenge for computer science is

to journey through the gateway event obtained by breaking our current classical computational assumptions, and thereby develop a mature science of Non-Classical Computation
  author = "Susan Stepney and Samuel L. Braunstein and John A. Clark and Andy Tyrrell
            and Andrew Adamatzky and Robert E. Smith and Tom Addis and Colin Johnson
            and Jonathan Timmis and Peter Welch and Robin Milner and Derek Partridge",
  title = "Journeys in Non-Classical Computation {I}:
           A Grand Challenge for computing research",
  journal = "International Journal of Parallel, Emergent and Distributed Systems",
  volume = 20,
  number = 1,
  pages = "5--19",
  month = mar,
  year = 2005 )