eXtensible Access Control Markup Language (XACML) is an OASIS standard allowing for XML-based communication of access control policy statements and assertions. XAMCL facilities the deployment of attribute-based access control, which is a superset of systems such as role-based access control (RBAC).
References:
https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=xacml
https://www.oasis-open.org/committees/download.php/2713/Brief_Introduction_to_XACML.html
http://www.itu.int/ITU-T/studygroups/com17/tutorials/tutorial_2006_04_25_barbir.pdf