Advanced Database Management System - Tutorials and Notes: Codd's Twelve Rules - Rule 8 - Physical Data Independence

Monday, 23 February 2015

Codd's Twelve Rules - Rule 8 - Physical Data Independence


Codd's Twelve Rules - Rule 8 - Physical Data Independence



Rule 8
Physical Data Independence
Rule
Changes in the physical level must not lead to a change in the next higher level called logical level.
Description
Any change in the physical level (lowest level that talks about how data is stored in a database, say for example, in arrays or linked lists etc.) must not lead to a change in the logical level (tables, columns, rows etc.).
Applications that are defined on the physical level should be able to continue to work even when changes are made to the internal implementation of data storage and access methods.
The way the data stored physically must be independent of how its accessed logically.
Example
For example, relations are stored as unordered files. If the change from unordered files to some other representation would not require a change in the table design, attribute types etc.
Some DBMS that fulfills this property
Almost all Relational DBMSs support this property.



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