Software Reliability: Philosophical Underpinnings.

Discusses qualities, such as flexibility, modifiability, creativity, and power, that can be inhibited by overemphasizing small-scale reliability. Is a system that always produces a given output for a given input more reliable than one producing better output for the most important inputs? Rigid hierarchical systems have high reliability at low levels but cannot compensate for incompetence or immorality at the top. Democratic, diffused organizations may mishandle details but are not incapacitated by leadership failure and are likelier to respond suitably to complex problems. Tight organization produces rigidity and inability to innovate. In software systems (1) nonhierarchical control flow may prove more fault tolerant; (2) loosely coupled modules may combine reliability and modifiability; (3) software should be instrumented for runtime fault diagnosis (dynamic reliability); (4) dealing with complex constraints may require internal debate; and (5) properties needed for large-scale system reliability may be incompatible with small-scale reliability. The poem "The Blind Men and the Elephant" is appended. (Prepared for 1975 International Conference on Software Reliability, Los Angeles.) 20 pp. Ref.