Data models are the foundation of an application. Getting them right at the beginning is much easier than changing the foundation later because, at the design stage, all of the changes you need to make can be done with papers and pencils. On the other hand, making a change to data models during the implementation of the application usually involves modifying all of the code through each layer of the application, and as we mentioned before that changes are unavoidable, building good data models can help you make those changes much easier.

In this chapter, we will design the data models of the TaskAgile application, and you will learn the following:

• The basics of data modeling
• The goals of doing data modeling
• Conceptual data modeling with ER diagrams
• Logical data modeling
• Physical data modeling for RDBMS
• Physical data modeling for MongoDB