SR (Synchronizing Resources) is a language for writing concurrent programs,
developed in the University of Arizona.  The main language constructs are
resources and operations.  Resources encapsulate processes and variables
they share; operations provide the primary mechanism for process interaction.

SR provides a novel integration of the mechanisms for invoking and servicing
operations.  Consequently, all local and remote procedure call, rendezvous,
message passing, dynamic process creation, multicast, and semaphores are
supported.  SR also supports shared global variables and operations.  Has a
nice interface (X11 and xtango).

SR is the predecessor to the MPD programming language, which provides the
same capabilities using different syntax.

WWW: http://www.cs.arizona.edu/sr/