Comment on “A framework to practical predictive maintenance modeling for multi-state systems” by Tan C.M. and Raghavan N. [Reliab Eng Syst Saf 2008;93(8):1138–50]

“System-perspective” proposed by “A framework to practical predictive maintenance modeling for multi-state systems” by Tan C.M. and Raghavan N. [A framework to practical predictive maintenance modeling for multi-state systems. Reliab Eng Syst Saf 2008;93(8):1138–50] is a very useful method to evaluate and optimize the maintenance strategy for complex systems, especially for multi-state systems (MSS). The commented paper proposes an innovative process and modeling method to present imperfect maintenance effects on MSS, but there exist some incorrect points and misunderstandings. In this paper, these problems are pointed out and are attempted to be corrected under the original framework of the commented paper.