Access control matrix in computer science, introduced by Butler W. Lampson in 1971, is a security model of protection states. Access control matrix describes the privileges of each subject with respect to every object in the computer system.
Access control matrix defines the protection state of a computer system in two basic parts, one denotes the object and other denotes the subject. Object is a set of entities that contains files, memory pages, etc. whereas the subject set contains user, process, etc as set entity. Moreover, in access control matrix, there exist some privileges that actually define access policies to the subject in order to process the object.
Access control matrix