In the Rendezvous domain in Ptolemy II, each actor executes in its own thread of control, and communication between actors is by rendezvous. If an actor is ready to send a message, it blocks until the receiving actor is ready to receive it. Similarly if an actor is ready to receive a message, it blocks until the sending actor is ready to send it.
This domain supports both conditional and multi-way rendezvous. In conditional rendezvous, an actor is willing to rendezvous with any one of several other actors. In multiway rendezvous, an actor requires rendezvous with multiple other actors at the same time. When using conditional rendezvous, the choice of which rendezvous occurs is nondeterministic, in general.
The model of computation is based on the CSP model first proposed by Hoare in 1978. Rendezvous-based communication is also known as synchronous message passing, but we avoid this term to avoid confusion with the SR (synchronous/reactive) domain.