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Evolution of Data Models

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The Evolution of Data Models
The quest for better data management has led to different models that attempt to resolve the file system’s critical shortcomings. Because each data model evolved from its predecessors, it is essential to examine the major data models in roughly chronological order.

1.1 The Hierarchical Model
A Hierarchical Database Model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only parent. All attributes of a specific record are listed under an entity type.

Example of a hierarchical model
In a database an entity type is the equivalent of a table. Each …show more content…

Codd.

The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.

Diagram of an example database according to the Relational Model

The relational model of data permits the database designer to create a consistent, logical representation of information. Consistency is achieved by including declared constraints in the database design, which is usually referred to as the logical schema. The theory includes a process of database normalization whereby a design with certain desirable properties details are handled by the DBMS engine, and are not reflected in the logical model. This contrasts with common practice for SQL DBMS in which performance tuning often requires changes to the logical model.

Advantages 1. Structural independence 2. Improved conceptual simplicity 3. Easier database design, implementation, management, and use 4. Ad hoc query capability 5. Powerful database management system

Disadvantages 1. Substantial hardware and system software

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