A CONCEPTUAL MODEL OF MULTI-VERSION SOFTWARE
Bev Littlewood, Douglas R. Miller · 2005
Recent work by Eckhardt and Lee shows that independently developed program versions will fail dependently: specifically that simultaneous failure of several versions is greater than would be the case under true independence. We show there is a precise duality between inpuc choice and program choice in this model and consider a generalisation in which different versions may be developed using diverse methodologies. 'The use of diverse methodologies is shown to decrease the probability of simultaneous failure of several versions. For certain I-out-of-n systems we obtain an optimal method for allocating diversity between versions. For 2-nut-of-3 systems there seem to be no simple optimality results which do not depend on constraints which cannot be verified in practice.