EF Code 12 Rules for RDBMS

EF Code 12 Rules for  RDBMS

Edger Frank “Ted ” code(august 1923-18 April 2003) was an English computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational database Code proposed thirteen rules, numbered 0 to 12.

 According to him if a database meets these rules, it can be called relational database management system.  The system must qualify as relational as a database and as a management system. For a system to qualify as a relational database management system, that system must use its relational facilities to manage database.

The other 12 rules derive this rule.

All information (including metadata) is stored to be represented as stored data in cells of table. The rows and columns have to be strictly unordered Each unique piece of data (atomic value) should be accessible by Table Name + Primary key (row) + Attribute (column)NULL has several meanings, it can mean missing data, not applicable or no value. It should be handled consistently. Primary key must not be NULL. Expression on NULL must give NULL. Database dictionary must have description of Database. Catalogue to be governed by same rule as rest of the database. The same query language to be used on catalogue as on applicable database. One well defined language must be there to provide all manners of access to data Eg SQL

All view that are theoretically updatable should be updatable by the system View is a virtual table There must be Insert, Delete, Update operations at each level of relations. Set operation like Union, Intersection and minus should also be supported. The physical storage of data should not matter to the system. If say some file supporting table were renamed or moved from one disk to another, it’s should not affect the application. If there is change in the logical structure (table structure) of the database the user view of data should not change. Say, if a table is split into two tables, a new view should give result as the join of the two tables. This rule is most difficult to satisfy. The database should be able to conforce its own integrity rather than using other programs. Key and check constraints. Trigger etc should be stored in data Dictionary. This also make RDBMS impendent of front end. A database should work property regardless of its distribution across a network. This lays foundation of distributed database. If low level Access is allowed to a system it should not be able to subvert or by pass integrity rule to change data. This can be achieved by some sort of looking or encryption