A flexible access control model for workflows

Access control models proposed so far can not satisfy the complicated access requirements in workflow systems very well. To address the issue, a flexible access control model for workflows is proposed in this paper, in which tasks and dependencies between tasks in workflows are classified and defined from the access control´s point of view, and for different types of tasks, different authorization strategies will be applied. Concepts of task amount and task authorization threshold are proposed for collaborative tasks. By the introduction of authorization policies, the flexible definition of task-related authorization is realized and the permission-relationship between senior and junior roles for a role hierarchy can be controlled flexibly. Furthermore, authorization-policy-related constraints are defined for the description of complicated security requirements associated with tasks. Effective static and dynamic conflict detection and resolution rules for constraints are also provided.