As a result of our experience, the SR distributed programming language has evolved. One change is that resources and processes are now dynamic rather than static. Another change is that operations and processes are now integrated in a novel way: all the mechanisms for process interaction — remote and local procedure call, rendezvous, dynamic process creation, and asynchronous message passing — are expressed in similar ways. This paper explains the rationale for these and other changes. We examine the fundamental issues faced by the designers of any distributed programming language and consider the ways in which these issues could be addressed. Special attention is given to the design objectives of expressiveness, simplicity, and efficiency.