Three Level ANSI SPARC Architecture
The three-level architecture seeks to keep each user's perception of the database independent from the database's actual representation.
External Level of ANSI SPARC Architecture:
This level provides users with a view of the database from their perspective. It describes the data in the database that is relevant to a particular user. The external level is composed of various external database views, offering a tailored presentation of entities, attributes, and relationships desired by the user. It's important to note that the same data can be interpreted differently by different users. For instance, one person may interpret "name" as (firstname, lastname), while another may see it as (firstname, lastname) or (lastname, firstname).
Conceptual Level of ANSI SPARC Architecture:
The conceptual level represents entities, their attributes, and their relationships, elucidating what data is stored in the database. It includes information on the data's semantics, security, and integrity. Positioned as the middle or second level in the three-level architecture, this level encompasses the entire logical structure of the database. It provides the organization's overall perspective on the database, irrespective of storage requirements.
Internal Level of ANSI SPARC Architecture:
At the internal level, the database is physically represented on the computer. This level focuses on the physical implementation of the database to optimize storage space utilization, runtime performance, and employs data encryption techniques. Interacting with the operating system, it manages tasks such as placing data in storage files, creating storage space, and retrieving data. The internal level deals with the nitty-gritty of how the data is stored and processed within the computer system.
