================================================================================
P9314   J.A. Bergstra, I. Bethke & A. Ponse
        "Process algebra with iteration"


We introduce iteration in process algebra by means of (the binary version
of) Kleene's star operator:  x * y is the process that chooses between
x and y, and upon termination of x has this choice again. It is proved that
adding respectively interleaving, communication and abstraction operators
increases expressivity up to the regular processes.  However, if the
distinction between (successful) termination and deadlock is dropped, ACP
(the Algebra of Communicating Processes, [BK84b]) with * is expressive up
to the regular processes.
Finally, some attention is paid to other iteration operators and fairness
issues, and some open questions are formulated.

Note: An earlier version of this work was presented at the REX
Symposium, Noordwijkerhout, June 1--4, 1993.

Added note (9603): An adaptation of this report is published as [BBP94].

[BK84b] J.A. Bergstra and J.W. Klop.
        Process algebra for synchronous communication.
        Information and Computation, 60(1/3):109--137, 1984.

[BBP94] J.A. Bergstra, I. Bethke, and A. Ponse.
        Process algebra with iteration and nesting.
        Computer Journal, 37(4):243--258, 1994.