Data Models

Ø  Data Model is a logical structure of Database.

Ø  Data Models are fundamental entities to introduce abstraction in a DBMS.

Ø  It provides the conceptual tools for describing the design of a database at each level of data abstraction.

Ø  Data models define how data is connected to each other and how they are processed and stored inside the system.

Ø  A Data Model in Database Management System (DBMS) is the concept of tools that are developed to summarize the description of the database. 

Ø  Data Models provide us with a transparent picture of data which helps us in creating an actual database. It shows us from the design of the data to its proper implementation of data.

Ø  It describes the design of database to reflect entities, attributes, relationship among data, constraints etc.

Ø  It is the modelling of the data description, data semantics, and consistency constraints of the data.

Ø  Therefore, there are following four data models used for understanding the structure of the database:

1)   Relational Data Model: 

Ø  This type of model designs the data in the form of rows and columns within a table.

Ø  Thus, a relational model uses tables for representing data and in-between relationships.

Ø  Tables will contain multiple columns with unique names in the database

Ø  Tables are also called relations.

Ø  It is also known as record-based model (Fixed format records of several data types). Each record type defines a fixed no. of fields or attributes

Ø  The relational data model is the widely used model which is primarily used by commercial data processing applications.

Ø  Most widely used data models

2)    Entity-Relationship Data Model: 

Ø  An E-R model is the logical representation of data as objects and relationships among them.

Ø  These objects are known as entities, and relationship is an association among these entities.

Ø  It is widely used in database designing.

Ø  An entity is a real-world thing or object which is distinguishable from other objects

Ø  It is basically a conceptual design (Pictorial representation) of any database which is easy to design the view of data.

Components of ER Model:

o   Entity: An entity is referred to as a real-world object. It can be a name, place, object, class, etc. These are represented by a rectangle in an ER Diagram.

o   Attributes: An attribute can be defined as the description of the entity. These are represented by Eclipse in an ER Diagram. It can be Age, Roll Number, or Marks for a Student.

o   Relationship: Relationships are used to define relations among different entities. Diamonds and Rhombus are used to show Relationships.

3)    Object-Based Data Model: 

Ø  An extension of the ER model with notions of functions, encapsulation, and object identity, inheritance etc.

Ø  Object-Based Model = E-R Model + Object Oriented Features

Ø  Suppose if our front end is designed using OOP languages like C++, Java, C# etc then we need to have back end which also support front end, in that case we are in the need of Object-Based Model.

Ø  This model supports a rich type system that includes structured and collection types. 

Components of Object-oriented Data Model:       

Ø  Objects – 
An object is an abstraction of a real-world entity or we can say it is an instance of class. Objects encapsulates data and code into a single unit which provide data abstraction by hiding the implementation details from the user. For example: Instances of student, doctor, engineer in above figure. 

Ø  Attribute – 
An attribute describes the properties of object. For example: Object is STUDENT and its attribute are Roll no, Branch, Setmarks() in the Student class. 

Ø   Methods – 
Method represents the behavior of an object. Basically, it represents the real-world action. For example: Finding a STUDENT marks in above figure as Setmarks(). 

Ø   Class – 
A class is a collection of similar objects with shared structure i.e. attributes and behavior i.e. methods. 

4)     Semi-Structured Data Model: 

Ø  This type of data model is different from the other three data models.

Ø  The semi-structured data model allows the data specifications at places where the individual data items of the same type may have different sets of attributes

Ø  Two applications need to communicate with each other, and if they want to use Database then we can go for Semi-structured data model.

Ø  The Extensible Markup Language, also known as XML, is widely used for representing the semi-structured data.

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