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 Communicating Sequential Processesmodel 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.
In a relation group, there is no significance to the order in which relations are linked, unlike the order in which ports are linked to relations. Also, unlike links between relations and ports, there is no significance to multiple links between the same relations. Any two relations are either linked or not linked.
The MoMLParser includes a list of backward compatibility filters that make certain changes on models when read, handling such issues as actors being moved or renamed and parameter names being changed. The filters themselves are defined in ptolemy.moml.filter. If you have developed your own actors under earlier versions of Ptolemy II by writing your own Java files, you should recompile all your java code with the new release. In theory, copying the .class files should work, but recompiling is safer.