Pietro Mazzoleni Bruno Crispo Swaminathan Sivasubramanian Elisa Bertino XACML Policy Integration Algorithms. 2008 11 ACM Trans. Inf. Syst. Secur. 1 http://doi.acm.org/10.1145/1330295.1330299 db/journals/tissec/tissec11.html#MazzoleniCSB08