The three-schema architecture is a framework for database systems that separates the database into three levels of abstraction: the internal level, the conceptual level, and the external level. This architecture was proposed by the ANSI/X3/SPARC Study Group on Database Management Systems in 1975 and is designed to provide data abstraction and independence.

Three Levels of Schema Architecture

Internal Schema (Physical Level):

• Description: The internal schema defines the physical storage structure of the database. It includes details on how data is stored, indexed, and accessed. This level focuses on the efficiency of data storage and retrieval.
• Concerns: Storage allocation, file organization, indexing, and data compression.

Conceptual Schema (Logical Level):

• Description: The conceptual schema represents the logical structure of the entire database as perceived by the database administrator. It hides the physical storage details and provides a unified view of the data, defining entities, relationships, constraints, and data types.
• Concerns: Data models, relationships, constraints, and integrity rules.
• • • External Schema (View Level):

• Description: The external schema consists of multiple user views. Each view is a subset of the database tailored to the needs of a particular user or group of users. It provides a way to present data in different formats and structures to different users.
• Concerns: User-specific views, access control, and data customization.

Why Mapping Between Schema Levels is Needed

Mapping between the schema levels is crucial for the following reasons:

Data Abstraction:

• Purpose: Data abstraction hides the complexities of the database’s physical storage from users and applications. This allows users to interact with the database without needing to understand its underlying physical structure.
• Implementation: Mapping translates requests and data from one level to another, providing a seamless interface for users.

Data Independence:

• Logical Data Independence: The ability to change the conceptual schema without altering the external schemas or application programs. This ensures that modifications in the logical data structure do not affect how users view the data.
• Physical Data Independence: The ability to change the internal schema without impacting the conceptual schema. This allows changes in physical storage (like reorganization or optimization) without affecting the logical structure or user views.

Customization:

• User-Specific Views: Different users require different views of the data. Mapping allows the creation of customized views tailored to specific needs, enhancing usability and security.
• Access Control: By defining different external schemas, the system can enforce access control, ensuring users only see the data they are authorized to access.

Simplification of Database Management:

• Maintenance: Changes in data structure or storage mechanisms can be managed efficiently. Optimizations at the physical level can be performed without disrupting logical organization or user views.
• Consistency: Mapping helps maintain data consistency across different levels, ensuring that updates and changes propagate correctly.

The three-schema architecture is essential for managing data abstraction and independence in database systems. Mapping between the internal, conceptual, and external schemas provides a structured approach to handling the complexity of databases. It ensures that changes at one level do not adversely affect other levels, facilitates customization for different users, and supports efficient and consistent database management.

Blockchain is a decentralized, distributed ledger technology that records transactions in a secure, transparent, and immutable manner. Unlike traditional databases that are managed by a central authority, a blockchain is maintained by a network of nodes  that follow a consensus protocol to validate and record transactions.

Key Concepts of blockchain technology:

• Decentralization: Traditional databases are centralized with a single authority controlled by the data. Each node has copy of the blockchain and any updates to the ledger must be agreed upon by the network.
• Immutability: Once a transaction is recorded in a block and added to the blockchain, it can’t be altered. This is achieved through cryptographic hashing and linking of block.
• Transparency: Blockchain transactions are recorded on a public ledger that is visible to all participants. This ensures that all transactions can be independently verified, promoting trust and accountability.
• Security: Each participants has a unique private key used to sign transactions, ensuring authenticity and preventing unauthorized access.

Impact on Digital Transactions :

• Financial Services
• Supply Chain Management
•  Healthcare
• Voting System
• Real Estate

Impact on enhancing security and transparency in digital transaction:

• Cryptographic Techniques: Every transaction is hashed and linked to the previous transaction via cryptographic hashes. This creates a secure and unalterable chain of transactions. Digital Signature prevents unauthorized access and fraud.
• Consensus Mechanism: Requires computational work to validate transactions, making it difficult and expensive to alter transaction history.
• Public Ledger: Blockchain ledgers are typically public, allowing anyone to view transaction history. Every transaction is recorded in a public ledger, ensuring that all participants have the same information.
• Traceability:  Each transaction is time-stamped and linked to the previous transaction, creating a clear and traceable record from start to finish.
• Auditability: The immutable nature of blockchain provides a permanent audit trail, making it easy to conduct audits and verify transactions.

By leveraging decentralization, cryptographic security, immutability, and transparency, blockchain provides a robust solution for a wide range of applications. As the technology evolves and overcomes current challenges, it has the potential to revolutionize various industries, making processes more secure, efficient, and trustworthy.