Strong Stability in an (R, s, S ) Inventory Model Boualem RABTA * and Djamil A ¨ ISSANI L.A.M.O.S. Laboratory of Modelization and Optimization of Systems University of Bejaia, 06000 (Algeria) E-mail : lamos bejaia@hotmail.com Abstract In this paper, we prove the applicability of the strong stability method to inven- tory models. Real life inventory problems are often very complicated and they are resolved only through approximations. Therefore, it is very important to justify these approximations and to estimate the resultant error. We study the strong stability in a periodic review inventory model with an (R, s, S ) policy. After showing the strong v-stability of the underlying Markov chain with respect to the perturbation of the demand distribution, we obtain quantitative stability estimates with an exact computation of constants. Keywords : Inventory control, (R, s, S ) policy, Markov chain, Perturbation, Strong Stability, Quantitative Estimates. Introduction When modelling practical problems, one may often replace a real system by another one which is close to it in some sense but simpler in structure and/or components. This approximation is necessary because real systems are generally very complicated, so their analysis can not lead to analytical results or it leads to complicated results which are not * Corresponding author : Boualem RABTA, L.A.M.O.S., Laboratory of Modelization and Optimization of Systems, University of Bejaia, 06000 (Algeria). Tel : (213) 34 21 08 00. Fax : (213) 34 21 51 88. E-mail : brabta@yahoo.fr. 1