Elisa Bertino Elena Ferrari Vijayalakshmi Atluri The Specification and Enforcement of Authorization Constraints in Workflow Management Systems. 65-104 1999 2 ACM Trans. Inf. Syst. Secur. 1 http://doi.acm.org/10.1145/300830.300837 db/journals/tissec/tissec2.html#BertinoFA99