XACML (Extensible Access Control Markup Language) is an open standard XML-based language designed to express security policies and access rights to information for Web services, digital rights management (DRM), and enterprise security applications. Ratified by the Organization for the Advancement of Structured Information Standards (OASIS) in February 2003, XACML was developed to standardize access control through XML so that, for example, a worker can access several affiliated Web sites with a single logon. XACML is sometimes referred to as Extensible Access Control Language (XACL).
XACML was designed to work in conjunction with Security Assertion Markup Language (SAML), another OASIS standard. SAML defines a means of sharing authorization information, such as user passwords and security clearance, between security systems. A rules engine (a program that examines established rules and suggests behaviors that comply with them) with policies expressed in XACML can compare such information with established criteria to ascertain user rights. The XACML specifications were developed through a collaborative effort of OASIS members including IBM, Sun Microsystems, and Entrust.