@Article{Kahl-2001a,
  author = 	 {Wolfram Kahl},
  title = 	 {Parallel Composition and Decomposition of Specifications},
  journal = 	 {Information Sciences},
  year = 	 {2001},
  volume = 	 {139},
  number = 	 {3--4},
  pages = 	 {197--220},
  month = 	 DEC,
  URL = {http://www.elsevier.com/gej-ng/10/23/143/95/33/30/abstract.html},
  abstract = {In the discipline of derivation of programs from specifications
     by refinement the \emph{demonic calculus of relations} is a
     well-established tool, which allows the use of
     \emph{demonic} operators on relations considered as
     specifications of a program's input-output-behaviour together with
     the standard relation algebraic operators to reason about
     specifications ordered by the \emph{refinement} ordering.

     The central contribution of this paper is
     the introduction of a \emph{demonic product} operator
     that embodies a natural concept of parallel composition of specifications.
     Of course, this raises the question of parallel decomposition,
     which in turn motivates the introduction of \emph{demonic implication}
     and \emph{totalisation} operators.
     Finally, we also present first results concerning parallel decomposition.}
}