SSC IMD SA 2017 – Question 140

Which of the following is included in the global table implementation of an access matrix?

• Domain
• Object
• Right-set
• All options are correct

Detailed Explanation:

The correct answer is d) All options are correct (सभी विकल्प सही हैं).

In operating systems, the Access Matrix is an abstract model for specifying protection states. One common method of implementing this matrix is the Global Table approach:

• The Global Table is the simplest implementation of an access matrix, stored as a centralized table consisting of ordered triples:$$\langle \text{Domain}, \text{Object}, \text{Rights-Set} \rangle$$
• Domain ($D$): Identifies the protection domain of the executing process.
• Object ($O$): Identifies the specific hardware or software entity being accessed.
• Rights-Set ($R$): Specifies the set of allowable access operations (read, write, delete, execute).
• When an operation $M$ is attempted on object $O$ within domain $D$, the OS searches the global table for the entry $\langle D, O, R_k \rangle$ where $M \in R_k$. If found, the operation proceeds; otherwise, a protection violation is flagged.

Therefore, Domain, Object, and Rights-Set are all integral components of the Global Table implementation.