中文摘要：

针对目前的委托模型中只考虑撤销委托的权限，而不考虑被委托用户所做的分配任务，提出了委托任务、撤销任务的概念。在基于任务角色的访问控制模型的基础上增加了时间约束条件，扩展了一种新的模型一带时间约束的基于任务角色的委托模型（TTRBDM）；给出了形式化的定义及其表示，分析了模型的委托和撤销的机制，给出了委托授权规则，最终理论证明了此模型的委托可控性。

英文摘要：

In current delegation models, the delegation permission was only considered, but the tasks , which were assigned users to finished, were ＇ t considered. This paper presented the delegation task and the revocation task. Based on the role-based access control model, expanded a new model, named task-role-based delegation model with time constraints, which was added time constraint mechanism. Addressed its formal definition, expression and authorization rule, and analyzed its delegation and revocation too. Finally proved the delegation mechanism theoretically to be controllability.