Database Models

The database models can be widely classified into two ways:

•    Record-based Model
•    Object-based Model

The Object-based model is used to describe the collection of tools that elaborate the data, data relationships etc. The record-based model as the name says describes the access methods of a DBMS and the data structures.

Record-based Model

The Record-based model consists of three kinds of models:
•    Hierarchical Model
•    Network Model
•    Relational Model

In the HIERARCHIAL MODEL, data is located in the form of parent-child relationship. It is more like a tree explodes and structure from a parent to one or more children in the tree. The parent is known as root and the children or branches are known as nodes. The last node is called the leaf node. Data stored at variant levels are accessible from the nodes.

The main disadvantage of this system is which; it is not possible to straightly enter a new node.

- In case of the NETWORK MODEL, parent-child relationship is not predictable since the data are going to be referred using pointers or locators that locate the data. Also any data connections can be made at the time of defining the data. The disadvantage of this kind of model is that it leads to complexity in the structure since data are accessed using locators.

- In 1970s Dr. Edgar F. Codd first introduced the RELATIONAL MODEL. It was an attempt to simplify the data structure. In the database all the data are represented using a tabular structure or a simple row- column type.