Computation proceeds by a sequence of messages, each transmitted by one agent and received by zero or more others. Transmission is autonomous, but reception is not. As in CCS, agents learn about the environment only through the messages they read. Programming such a system is hard because we have to ensure that messages are read.
Testing resembles a viva-voce examination.
Observation, restriction and hidden actions differ from their CCS counterparts, as does testing equivalence. We use transition systems with transmit, read and discard actions. Discards are self-loops, and only auxiliary. We have some results on strong bisimulation and testing, but much work remains to make CBS tractable. Updated and subsumed by the consolidating journal paper on CBS , but not all of the ideas here appear there.