Domain-driven design separates the model layer “M” of MVC into an application, domain and infrastructure layer. The infrastructure layer is used to retrieve and store data. The domain layer is where the business knowledge or expertise is. The application layer is responsible for coordinating the infrastructure and domain layers to make a useful application. Typically, it would use the infrastructure to obtain the data, consult the domain to see what should be done, and then use the infrastructure again to achieve the results.