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· A data model describes how the data can be represented and accessed from a software after complete implementation
· It is a simple abstraction of complex real world data gathering environment.
· The main purpose of data model is to give an idea as how the final system or software will look like after development is completed.
ollowing are the different types of a Data Model
1. Hierarchical Model
2. Relational Model
3. Network Database Model
4. Entity Relationship Model
5. Object Model
Hierarchical model was developed by IBM as Information Management System.
In Hierarchical model, data is represented as a simple tree like structure form. This model represents a one-to-many relationship ie parent-child relationship. One child can have only one parent but one parent can have many children. This model is mainly used in IBM Main Frame computers.
The Relational Database model was first proposed by E.F. Codd in 1970 . Nowadays, it is the most widespread data model used for database applications around the world.
The basic structure of data in relational model is tables (relations). All the information’s related to a particular type is stored in rows of that table. Hence tables are also known as relations in a relational model. A relation key is an attribute which uniquely identifies a particular tuple (row in a relation (table)).
Network database model is an extended form of hierarchical data model. The difference between hierarchical and Network data model is :
· In hierarchical model, a child record has only one parent node,
· In a Network model, a child may have many parent nodes. It represents the data in many-to-many relationships.
· This model is easier and faster to access the data.
School represents the parent node
Library, Office and Staff room is a child to school (parent node)
Student is a child to library, office and staff room (one to many relationship)
In this database model, relationship are created by dividing the object into entity and its characteristics into attributes.
It was developed by Chen in 1976. This model is useful in developing a conceptual design for the database. It is very simple and easy to design logical view of data. The developer can easily understand the system by looking at ER model constructed.
Rectangle represents the entities. E.g. Doctor and Patient
Ellipse represents the attributes E.g. D-id, D-name, P-id, P-name. Attributes describes the characteristics and each entity becomes a major part of the data stored in the database.
Diamond represents the relationship in ER diagrams
E.g. Doctor diagnosis the Patient
Object model stores the data in the form of objects, attributes and methods, classes and Inheritance. This model handles more complex applications, such as Geographic information System (GIS), scientific experiments, engineering design and manufacturing. It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.
An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model.
· Circle has the attribute radius.
· Rectangle has the attributes length and breadth.
· Triangle has the attributes base and height .
· The objects Circle, Rectangle and Triangle inherit from the object Shape.
Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.
Application Programmers or Software Developers
This user group is involved in developing and designing the parts of DBMS.
All modern applications, web or mobile, store user data. Applications are programmed in such a way that they collect user data and store the data on DBMS systems running on their server. End users are the one who store, retrieve, update and delete data.
Database designers: are responsible for identifying the data to be stored in the database for choosing appropriate structures to represent and store the data.
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