grid naming abstraction is attached to the process list;
each process is specified by a 
pair (e.g., in the PO Box).
Through inheritance, row and column mailers are defined in each process
as the appropriate subsets of the two-dimensional grid. This class has
received the most extensive use because of the natural application to
linear algebra and related computations.
Class-specific primitives for G2-Class mail have been defined for both higher efficiency and better abstraction. Small-g calls require mailer specification while big-G calls do not, analogous to the y- and Y-type calls defined generically above.