1. ACCESS MATRIX
Wayne De Souza
411107

2. An Access Matrix is an abstract model of protection.
The rows of it represent the domains and the columns represent objects.
Every entry in the access matrix consists of a set of access rights.
The entry access(i,j) defines the set of operations that a process executing in domain Di can invoke on object Oj.

3. A process executing in domain Di can access objects specified in row i, and then also only as allowed by the entries.

4. The access matrix provides an appropriate mechanism for both the static and dynamic association between processes and domains.
We can switch a process from one domain to another by using the switch operation.
This is possible only if the domains are present as objects in d access matrix.
Switching between domains is allowed only if the matrix entry between the two domains in question has the access right switch.

6. Access Matrix With Copy Rights
The ability to copy an access right from one row of the access matrix to another is denoted by an asterisk (*) appended to the access right.
A right is copied from accessi,j to access k,j and then removed from accessi,j.
Propagation of the copy right may be limited i.e. when the right R* is copied from accessi,j to accessk,j only the right R is copied (Not R*).

8. Access Matrix With Owner Rights
The owner right is the mechanism with which we can make modifications to rights like adding or removing rights.
If accessi,j includes the owner right, then a process executing in domain Di can add or remove any right in any entry of column j.

10. Access Matrix With Control Rights
The copy and owner rights allow a process to change the entries only in a column.
The mechanism with which we can change the entries in rows is called the control right.
It is applicable only to domain objects.
If accessi,j includes the control right, then a process executing in domain Di can remove any access right from row j.

12. Reference:-
Operating System Concepts
(Pgs ) – Galvin
Important Questions:-
Write a short note on Access Matrix [5mks]
(May/June 2012) (Nov/Dec 2011)

13. THANK YOU