Life Cycle Of A Relational Database

THE ESSENCE OF THE 12 SPECIFIC RULES ARE AS FOLLOWS:12 RULES

1.   Representation of information. All information in a relational database is represented explicitly at the logical level and in exactly one way- by values in tables.

2.   Guaranteed logical accessibility. Each and every datum (atomic value) in a relational database is guaranteed to be logically accessible by resorting to a combination of the table name, primary key value, and column name.

3.   Systematic representation of mission information. Null values (distinct form the empty character string or a string of blank characters and distinct from zero or any other number) are supported in a fully relational DBMS for representing missing information and inapplicable information in a systematic way independent of data type.

4.   Dynamic online catalog. The database description is represented at the local level in the same way as ordinary data, so that authorized users can query it in the same relational language that they use in working with the regular data.

5.   Comprehensive data sublanguage. A relational system may support several languages and various modes of terminal use. For example the fill-in-the-blanks mode. However, there must be at least one language whose statements are expressible, in some well-defined syntax, as character strings. Also, it must be comprehensive in supporting all of the following items.

·    Data definition

·    View definition

·    Data manipulation (interactive and by program)

·    Integrity constraints

·    Authorization

·    Transaction boundaries (begin, commit, and rollback)

6.   Updateable views. All views that are theoretically updateable are also updateable by the database system.

7.   High-level insert, update, and delete. The capability of handling a base relation or a derived relation as a single operand applies not only to retrieving data but also to inserting, updating, and deleting of data.

8.   Physical data independence. Application programs and terminal activities remain logically unimpaired whenever any changes are made in either storage representations or access methods.

9.   Logical data independence. Application programs and terminal activities remain logically unimpaired when information’s preserving appropriate changes for any kind are made to the base tables.

10. Integrity independence. Integrity constraints specific to a particular database must be definable in the relational data sublanguage and storable in the catalog. Not in the application program.

11. Distribution independence. Whether or not a system supports database distribution. It must have a data sublanguage that can support distributed databases without impairing the application programs or terminal activities.

12. No subversion. If a relational system has a low-level (single-record-at-a-time) language, that low-level language cannot be used to subvert or bypass the integrity rules and constraints expressed in the higher level relation language (multiple-records-at-a-time).