Abstract: Access control model defines the whole framework of security system access control. The existing access control models are mostly static authorization models. Although the models can be extended to realize local dynamic nature(such as activate roles temporary by defining conditions of them)，but they arc restricted by the cxtensional elements in real applications,and most of them can not describe the dynamic changes of the authorized process. To solve the problem,this paper proposed a dynamic access control model based on situation calculus(SCDAC). SCDAC describes the attributes and strategy of access control with logic facts and rules and treats the authorization state at an instance of time as a situation. It can achieve the changes of situation through actions, and portrays the preconditions of the action and successor state axioms. Finally an example was adopted to illustrate describing the dynamic changes of authorization states by SCDAC is feasible.

Key words: Access control model,Dynamic,Situation calculus