Yuri Demchenko Oscar Koeroo Cees de Laat Håkon Sagehaug Extending XACML authorisation model to support policy obligations handling in distributed application. 5 2008 MGC http://doi.acm.org/10.1145/1462704.1462709 conf/middleware/2008mgc db/conf/middleware/mgc2008.html#DemchenkoKLS08