A Calculus of Broadcasting Systems
Paper in proceedings, 1991
CBS is a simple and natural CCS-like calculus where processes speak one at a time and are heard instantaneously by all others. Speech is autonomous, contention between speakers being resolved nondeterministically,
but hearing only happens when someone else speaks.
Observationally meaningful laws dier from those of CCS. The change
from handshake communication in CCS to broadcast in CBS permits several
advances. (1) Priority, which attaches only to autonomous actions,
is simply added to CBS in contrast to CCS, where such actions are the
result of communication. (2) A CBS simulator runs a process by returning
a list of values it broadcasts. This permits a powerful combination,
CBS with the host language. It yields several elegant algorithms. Only
processes with a unique response to each input are needed in practice, so
weak bisimulation is a congruence. (3) CBS subsystems are interfaced by
translators; by mapping messages to silence, these can restrict hearing
and hide speech. Reversing a translator turns its scope inside out. This
permits a new specification for a communication link: the environment
of each user should behave like the other user.
This paper reports the stable aspects of an evolving study.