“…At the ends of this spectrum lie the renewal process (Ross, 1996) and the non-homogeneous Poisson process (Cox and Lewis, 1966). In between, and thus capturing imperfect repair, lie mixed processes (Brown and Proschan, 1983;Kallen, 2011;Doyen, 2014) virtual age-reduction models (Kijima and Sumita, 1986;Kijima, 1989;Jack, 1998;Tanwar et al, 2014), geometric processes (Lam, 1988;Wang and Pham, 1996;Wu and Clements-Croome, 2006;Wu and Scarf, 2015;Zhang et al, 2015;Wu and Wang, 2018), hazard-reduction models (Doyen and Gaudoin, 2004;Percy and Alkali, 2006;Percy et al, 2010), virtual component models (Wu and Scarf, 2017); and generalizations of these (Doyen et al, 2017). All these attempt to model multicomponent systems parsimoniously.…”