An improved role hierarchy model is introduced against the drawback of RBAC96;some new concepts such as public permission, private permission and scope of inheritance are presented in the model.

By using the concepts of role-permission inheritance limit and extreme limit in the relation of role-permission assignment,the role permissions are divided into private permissions and public ones,and the concepts of privatizing inheritance and publicizing inheritance are defined.

In order to overcome shortages of the processing method of RBAC96 model′s private permission,an improved model is put forward from a point of implementation view.

Due to the fact that foreign companies defeated Chinese companies in water industry with the strategy of "High Price, Unfair Competition" , this paper analyses the management of Limited Real Right, and presents its benefits to Chinese Water market.