DBMS > Data Model > What is Entity Relationship Model?

Entity-Relationship Model (ER Model)

ER model is a high-level view of database. This model was designed by Peter Chen and published in 1976 papers. It is the logical representation of data as objects and relationships among them. 

Using this model, we represent the real-world problem in the pictorial form to make it easy for the stakeholders, developers to understand by just looking at the ER diagram. ER diagram as a visual tool to represent an ER Model. ER diagram has the following three components:

Entities: Entity is a real-world thing. Entity can be a person, place, or even a concept. Example: Teachers, Students, Course, Building, Department, etc. are some of the entities of a Student Management System.

Attributes: An entity contains a real-world property called attribute. This is the characteristics of that entity. Example: The entity student has the property like student id, name , registration date, department etc.

Relationship: Relationship tells how two attributes are related. Example: student admitted into a department.

 

In the above diagram, the entities are Student, Program and Department. Entities student and department are connected using the relationship. Hence  student and program, department and program are connected.  Here, each sudent admitted into a department, each dudent admitted into a program and each program are running under a department. 

Features of ER Model

• Graphical Representation for Better Understanding: It is very easy and simple to understand so it can be used by the developers to communicate with the stakeholders.
• ER Diagram: ER diagram is used as a visual tool for representing the model.
• Database Design: This model helps the database designers to create the database and is widely used in database design.

Advantages of ER Model

• Simple: Basically ER Model is very easy to build. Once we have the relationship between the attributes and the entities in hand we can easily build the ER Diagram for the model.
• Effective Communication Tool: This model is used widely by the database designers for communicating their ideas with other stakeholders.
• Easy Conversion to any Model: This model depicts well to the relational model and can be easily be  converted relational model into the tables. This model can also be converted to any other model like network model, hierarchical model etc.

Disadvatages of ER Model
No industry standard for notation: There is no industry standard for developing an ER model. So one developer might use notations which are not understood by other developers.
Hidden information: Some information might be lost or hidden in the ER model. As it is a high-level view so there are chances that some details of information might be hidden.

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