Current parallel programming languages support only a narrow range of
programming styles; force programmers to bind the specification of
parallelism too early in program development; and limit the class of
architectures for which they are effective.  This paper presents a
model for parallel programming based on uniform encapsulation and
control, concurrent operations on objects, synchronous invocation with
early reply, references to code in an environment, and a copy model of
parameters and variables.  This simple, coherent model enables
programmers to use different styles of programming and to bind
parallelism late in program development.  In addition, the model may be
efficiently implemented on a wide range of multiprocessor
architectures.