Domain Driven Design or DDD for short is a huge but interesting topic. It has many complex subjects focused on business and technical perspectives. In the technology industry, people always talk about how both perspectives should work together in order to give the business benefits. However, that is not an easy task and it is when DDD appears in the scene. In this course, you are going to learn the most important concepts of DDD. You will see some concerns, techniques to model, how DDD can be implemented using hexagonal architecture and many other amazing concepts.

Domain Driven Design (DDD) Made Easy

Continuing with the example regarding a restaurant, let us implement the use case layer on top of the domain.


# Example definition
The business case that is being implemented is related to a restaurant that wants to allow a customer to order something by using its website. The idea is to expose an **API** to fulfill this business case. It is required to comply with these business rules: 
* If a customer has no created orders, it is possible to create a new one
* If a customer has already created orders, it is not possible to create a new one  

## Model definition
The following diagram depicts the use case layer that defines two artifacts. Additionally, this layer makes use of the domain layer.


Learn what the use case layer in hexagonal architecture is and how to implement it.

Introduction

Mapping Domain to Model

Domain Activities

Domain Objects

Domain Abstractions

Hexagonal Architecture

Use Case Layer

Example definition