Describe any five of the 12 commandments formulated by C. J. Date for distributed databases

Answer 1

With the rise of relational databases, most vendors implemented their own versions of distributed databases, generally highlighting their respective product's strengths. To make comparisons easier, C. J. Date formulated 12 "commandments" or basic principles of distributed databases. Although no current DDBMS conforms to all of them, they constitute a useful target. Students may choose any five of the following 12 commandments and describe them:

Rule 1: Local-site independence.
Each local site can act as an independent, autonomous, centralized DBMS. Each site is responsible for security, concurrency control, backup, and recovery.

Rule 2: Central-site independence.
No site in the network relies on a central site or any other site. All sites have the same capabilities.

Rule 3: Failure independence.
The system is not affected by node failures. The system is in continuous operation even in the case of a node failure or an expansion of the network.

Rule 4: Location transparency.
The user does not need to know the location of data to retrieve those data.

Rule 5: Fragmentation transparency.
Data fragmentation is transparent to the user, who sees only one logical database. The user does not need to know the name of the database fragments to retrieve them.

Rule 6: Replication transparency.
The user sees only one logical database. The DDBMS transparently selects the database fragment to access. To the user, the DDBMS manages all fragments transparently.

Rule 7: Distributed query processing.
A distributed query may be executed at several different data processor sites. Query optimization is performed transparently by the DDBMS.

Rule 8: Distributed transaction processing.
A transaction may update data at several different sites, and the transaction is executed transparently.

Rule 9: Hardware independence.
The system must run on any hardware platform.

Rule 10: Operating system independence.
The system must run on any operating system platform.

Rule 11: Network independence.
The system must run on any network platform.

Rule 12: Database independence.
The system must support any vendor's database product.