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Data Models: 

# Data Model is a collection of conceptual tools that are used to describe data, relationships among data, consistency constraints, and data semantics.

# The relation model of data is the most widely used model today.

Data Models can be categorized as follows: 

The data model is a concept under the Abstraction Level.

High-Level or Conceptual Model: Provide concepts about how the data are perceived by users. Generally, users do not aware of the database and DBMS, so in that case, some diagrams (picture view) are used to represent the database or total function to the user or client. Here E-R diagram is used popularly used.

Representational or Implementation Data Model 

In this layer data which are stored into tables are represented and manipulated by SQL. 

Physical Data Model: 

Here define the structure of the schema, database, data – dictionary and how they are stored and related. And also store how to access table and all.

The database will be completed if we complete these three above three data models. 

Apart from these above models, some other models are described as follows:

• Object-oriented data model- This model incorporates the features like encapsulation, methods or functions, and object identity. It extends the features of the E-R model.

• Object-relational data model- This model incorporates the features of both the Object-oriented data model and relational data model.

• Semi-structured data model- This model allows having a different set of attributes for the same type of data. The extensible markup language (XML) is used to represent Semi-structured data.