I. INTRODUCTION
Compared with the off-line scheduling in which all related tasks information have been pre-determined at the decision point, the job shop on-line scheduling fully represents the dynamic stochastic characteristic of modern scheduling. In the solving procedure, the original problem constantly varies because of the additions or deletions of the new variables and constraints. The existing methods, which usually focus on the static model, can hardly apply to the production environment in which the factors of job attributes, the resources availability and etc are randomly distributed [1] [2].