Every business application is faced with different kinds of problems throughout the development. The goal of domain-driven design is to isolate the complexity of an application, making it easy to change and maintain, by providing a language as well as a set of rules for the interaction of objects in the domain.

As we have seen throughout the book, domain-driven design is all about modeling business logic, so it can be accessible for domain experts to judge and evaluate. This is an important part of an application and, if done right, it can save a lot of trouble throughout the development cycle. When driving an application through domain-driven design, we need to identify the core domain and its subdomains. Depending on what our domain is about, the pure business complexity that is there to model is, not the only complexity so.

Neither is every application complex for the business rules, nor does every application lend itself nicely to being modeled in an object...