Ricardo Nabhen Edgard Jamhour Carlos Maziero A Policy-based Framework for RBAC. 181-193 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2867&spage=181 2003 conf/dsom/2003 DSOM db/conf/dsom/dsom2003.html#NabhenJM03