An abstract design standard for DBMS is ANSI SPARC. ANSI SPARC stands for American National Standards Institute, Standards Planning And Requirements Committee started in 1975. Follow this link to know more about it HERE
The ANSI SPARC paradigm never adopted as a formal standard. No current DBMS systems are entirely based on it( they usually lack complete physical independence and disallow a direct user access to the conceptual level).
Three Level Architecture
Structure of Three Level Architecture
The Three Levels are:
External Level: A user’s database view specifies a section of the database that is relevant to that user. It filters out irrelevant information as well as information that the user has no authority to see.
Conceptual Level: It expresses what data to keep and how it should connect across the database. The database’s physical storage is not specified at the conceptual level. The following are some key details concerning this level:
- Database architecture works at this level.
- Structure of all users.
- Independent of hardware and software.
Internal Level: The internal level is concerned with the physical representation of the database on the computer system. It explains how the data is saved in the database and on the computer hardware.
Three Level Architecture Separate’s the User’s view:
- It provides for separate customizable user views: Each user should have access to the same data but a distinct customised view of it. These should be self-contained: modifications to one should not have an impact on the others.
- It shields users from physical database storage specifics: Users should not have to deal with physical database storage details.
- The database administrator should be able to modify database storage structures without impacting users’ views.
- Changes to the physical features of the storage should have no effect on the database’s internal structure: A switch to a new disk is an example.
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