Date Added: Jul 2012
The purpose of access control models is to assign permissions to users. The most interesting would be to have the ability to set dynamic permissions, i.e., context-dependent. Contexts express different types of extra conditions or constraints that control activation of rules expressed in the access control policy. there are several types of context: the Temporal context that depends on the time at which the subject is requesting for an access to the system, the Spatial context that depends on the subject location, the User-declared context that depends on the subject objective (or purpose), and the Prerequisite context that depends on characteristics that join the subject, the action and the object.