A computer-implemented system (90) is provided that supports a high degree of separation between processing elements. The computer-implemented system (90) comprises a plurality of cells (92) residing on the computer-implemented system, where each cell (92) includes a domain of execution (94) and at least one processing element (96); a separation specification (99) that governs communication between the processing elements (96); and a kernel (98) of an operating system that facilitates execution of the processing elements (96) and administers the communication between the processing elements (96) in accordance with the separation specification (99), such that one processing element (96) can influence the operation of another processing element (96) only as set forth by the separation specification (99). In particular, the separation specification provides memory allocation, remote procedure calls and exception handling mechanisms.