Book Image

ASP.NET 3.5 Application Architecture and Design

By : Vivek Thakur
Book Image

ASP.NET 3.5 Application Architecture and Design

By: Vivek Thakur

Overview of this book

Table of Contents (14 chapters)
About the Author
About the Reviewers

Entity-Relationship Diagram

Entity-Relationship diagrams, or ER diagrams in short, are graphical representations depicting relationships between different entities in a system. We humans understand and remember pictures or images more easily than textual information. When we first start to understand a project we need to see how different entities in the project relate to each other. ER diagrams help us achieve that goal by graphically describing the relationships.


An entity can be thought of as an object in a system that can be identified uniquely. An entity can have attributes; an attribute is simply a property we can associate with an entity. For example, a Car entity can have the following attributes: EngineCapacity, NumberofGears, SeatingCapacity, Mileage, and so on. So attributes are basically fields holding data to indentify an entity. Attributes cannot exist without an entity.

Let us understand ER diagrams in detail with a simple e-commerce example: a very basic Order Management...