Ricardo Nabhen Edgard Jamhour Carlos Maziero A Policy Based Framework for Access Control. 47-59 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2836&spage=47 2003 conf/icics/2003 ICICS db/conf/icics/icics2003.html#NabhenJM03