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.