For the purpose of solving the current problems in the role-based network model ( RNM) , this paper improved RNM from two aspects: time constrained, and the inheritance relationship between roles. And it realized the time constrained role-based network model (TRNM) based on the improved RNM. This model not only inherited all the advantages of RNM, but also provided time constrained and the proper inheritance relationship between roles. This paper specified the development methods about TRNM in the end.%从当前角色网络模型(RNM)所存在的问题入手,通过加入时限约束和解决角色间继承关系上的缺陷对角色网络模型进行改进,并进一步提出基于时限约束的角色网络模型( TRNM).该模型在继承角色网络模型全部优势的同时,一方面解决了原有RNM中角色间继承关系上的缺陷,使高层角色可以部分继承底层角色的权限；另一方面则通过对时限约束特征的定义和分析,给出了在时限约束条件下TRNM的组成成员和形式化描述,最后具体给出了TRNM的开发方法流程.
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