Fred B. Schneider Kevin Walsh Emin Gün Sirer Nexus authorization logic (NAL): Design rationale and applications. 8 2011 14 ACM Trans. Inf. Syst. Secur. 1 http://doi.acm.org/10.1145/1952982.1952990 db/journals/tissec/tissec14.html#SchneiderWS11