Conceptual data modeling is the stage where we discover the data requirements by going through the requirements of an application. We document these data requirements as conceptual data models using Entity-Relationship (ER) diagrams, which is an informal standard of documenting data models.

Let's look at an example. Based on the Register user story and the Log in user story in the TaskAgile application as created in Chapter 4, TaskAgile - A Trello-like Task Management Tool, under Users the section, we can discover that we need to store users' data upon registration and also provide the ability to query each user's data based on a username or an email address during login.

Let's use the Create a team user story created in Chapter 4, TaskAgile - A Trello-like Task Management Tool, under the Teams section as another example. As a registered user, I want to create teams so that I can organize the tasks of different teams. We can discover that we will need to store the teams, and also the relationship between users and teams, which is who created which teams, and with a closer look, you can discover that we will also need to store the task's data and probably the relationship between tasks and teams. There are no further details for this data requirement, but we will get a better understanding of it once we finish analyzing all of the other user stories.