The Free On-line Dictionary of Computing (30 December 2018):

Kent Applicative Operating System
KAOS

    (KAOS) A functional operating system
   concept using dynamic process creation and inter-process
   communication.  KAOS was described in 1989 by Dr. John Cupitt
   in his PhD thesis at the University of Kent.  It was based on
   earlier work by Will R. Stoye.

   KAOS allowed dynamic creation of "functional processes" -
   functions that transform an input stream to an output
   stream.  Process scheduling is based on evaluation on demand.
   Inter-process communication is by message passing based on
   Stoye's sorting office concept.

   (2015-05-30)