# Introduction to Data Models

A data model is a collection of tools for describing data and the associated relationships, semantics and constraints.

There are several kinds of data models:

* Relational Model
* ER (Entity-Relationship) Model
* Object-Based Data Models (Object-Oriented and Object-Relational)
* Semi-Structured Data Models
* Other Models (Network Model, Hierarchical Model etc.)

## Relational Model

This model assumes each table to be a relation.

The attributes/relation names are represented as columns of the table and the values for the relations are represented in the rows of the table.

![](/files/-M5-0_5-cL4Ut7PICgMn)

The Relational Model is discussed in detail in later chapters.

## ER (Entity-Relationship) Model

This model describes a set of entities and the relationships between them. It is mainly used for database design.

## Object-Based Data Model

It is an extension of the relational data model. It includes object orientation and constructs to support additional data types.

## Semi-Structured Data Model

It was created to represent data where data items of the same type may have different attributes. It can represent the information of some data sources that cannot be constrained by schema.

Semi-structured data model uses XML (Extensible Markup Language).


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