Ideal Flow of Data for a Layered Web Application

Let's see what an ideal flow of data for a layered web application looks like. Have a look at the following diagram:

Let's analyze the diagram. Here's the explanation:

• The Browser is the medium through which the user types the URL
• The appropriate Controller gets into action
• The Controller communicates with the Business Layer and the Data Layer
• The Business Layer returns the data requested by the user to the Controller

The business and the data layers constitute the model part of the MVC. Now, what are these layers? The business layer's job is to put the business logic or functionality to use. The data layer concerns with external systems such as databases. It provides access to these systems.