In this note, the authors characterize the scope of the product form solution that has been presented in the paper, ‘A closed form solution for the G/M/r machine interference model’. In this paper, the machine interference problem has been solved for N heterogeneous machines that are ‘repaired’ by a set of r operatives, which repair the machines in a service-in-random-order fashion. The authors solve the model allowing for different, independent and identically distributed times between breakdowns for each machine and different negative-exponential repair times for each machine. In this short critique, they show that the solution presented by Bunday and Khorram does not solve the classical machine interference problem unless the hypothesis of heterogeneous machines is relaxed. [See IAOR 42750.]
