Answer
a), b), c)
Work Step by Step
a. Ensure that a user’s access to the database is restricted to the appropriate subschema
Yes, this is a core function of a DBMS.
It enforces authorization and access control, ensuring users can only access data they're permitted to see, often through views or subschemas.
b. Translate commands stated in terms of the database model into actions compatible with the actual data storage system
Yes, this is part of the query processing and optimization role of a DBMS. It translates high-level queries (e.g., SQL) into low-level instructions that interact with the physical storage.
c. Disguise the fact that the data in the database is actually scattered among many computers in a network
Yes, in the case of distributed databases, the DBMS provides data abstraction and transparency. It hides the complexity of data distribution, making the system appear as a single unified database to users.
So, the correct answer is: All of the above (a, b, and c).
