> For the complete documentation index, see [llms.txt](https://mun.gitbook.io/dbms/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mun.gitbook.io/dbms/database/view-of-data/data-models.md).

# Data Models

Data Model is the modeling of the data description, data semantics, and consistency constraints of the data. It provides the conceptual tools for describing the design of a database at each level of data abstraction.

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

* Relational Data Model
* Entity-Relationship Data Model
* Object-based Data Model
* Semi-structured Data Model

## Relational Data Model

* This model was described by Edgar F. Codd, in 1969.
* Data are designed in rows and columns within a table.
* Tables are used to represent data and relationships. 
* Tables are called relations.
* It is the widely used model by commercial data processing applications.

## Entity-Relationship Data Model

* This model was designed by Peter Chen and published in 1976.
* It is the logical representation of data as objects and relationships.
* These objects are known as entities, and relationship is an association among these entities.
* A set of attributes describe the entities. For example, name, email, phone describes a person entity.
* A set of the same type of entities is known as an 'Entity set', and the set of the same type of relationships is known as 'relationship set'.
* It was widely used in database designing.

## Object-based Data Model

* Object-based Data Model were developed in 1980s.
* It is an extension of the ER model with notions of functions, encapsulation, and object identity.
* Objects are data carrying its properties.
* It supports a rich type system that includes structured and collection types.

## Semi structured Data Model:

* It is different from the other three data models.
* Same data items may have different attributes sets.
* The Extensible Markup Language (XML) is widely used to represent semi-structured data.