Abstract: This paper proposes a role and task based workflow access control model, describes the relationship both the key elements of the model, static and dynamic constraints. And then an intuitive formal language called ERCL is proposed, which takes the model as context to specify workflow authorization constraints based on role and task. ERCL uses system functions, sets and variable symbols as its basic elements. Finally, gives a application of the model in a workflow system.

Key words: workflow, access control, role, task