Re: Where can i find the original database rules from Codd?

This is C.J Date's version of the 12 Rules from AN INTRODUCTION TO DATABASE SYSTEMS (5th edition) as set forth in pages 389 - 393

0. (Yes, there is a Rule 0!)

For a system to qualify as a RELATIONAL, DATABASE, MANAGEMENT system, that system must use its RELATIONAL facilities (exclusively) to MANAGE the DATABASE.

1. The information rule

The information rule simply requires all information in the database to be represented in one and only one way, Namely by values in column positions within rows of tables.

2. The guaranteed access rule

This rule is essentially a restatement of the fundamental requirement for primary keys. It says that every individual scalar value in the database must be logically addressable by specifying the mane of the containing table, the name of the containing column and the primary key value of the containing row.

3. Systematic treatment of null values

The DBMS is required to support a representation of "missing information and inapplicable information" that is systematic, distinct from all regular values (for example, "distinct from zero or any other number," in the case of numeric values), and independent of data type. It is also implied that such representations must be manipulated by the DBMS in a systematic way.

4. Active online catalog based on the relational model

The system is required to support an online, inline, relational catalog that is accessible to authorized users by means of their regular query language.

5. The comprehensive data sublanguage rule

The system must support a least one relational language that (a) has a linear syntax, (b) can be used both interactively and within application programs, and (c) supports data definition operations (including view definitions), data manipulation operations (update as well as retrieval), security and integrity constraints, and transaction management operations (begin, commit, and rollback).

6. The view updating rule

All views that are theoretically updatable must be updatable by the system.

7. High-level insert, update, and delete

The system must support set-at-a-time INSERT, UPDATE, and DELETE operators.

8. Physical data independence

Self-explanatory.

9. Logical data independence

Self-explanatory

1. Integrity independence

Integrity constraints must be specified separately from application programs and stored in the catalog. It must be possible to change such constraints as and when appropriate without unnecessarily affecting existing applications.

1. Distribution independence

Existing applications should continue to operate successfully (a) when a distributed version of the DBMS is first introduced; (b) when existing distributed data is redistributed around the system.

1. The nonsubversion rule

If the system provides a low-level (record-at-a-time) interface, then that interface cannot be used to subvert the system (e.g.) bypassing a relational security or integrity constraint.

Codd also specified nine Structural features, three Integrity features and eighteen Manipulative features all of which are required as well. I'd repeat them here but this note is already too long. Received on Mon Mar 01 2004 - 21:47:25 CET