DDD (Domain-Driven Design): Applying in Practice

14 Mar DDD (Domain-Driven Design): Applying in Practice

Introduction

Domain-Driven Design (DDD) is an approach to software development focused on modeling business domains. Created by Eric Evans, DDD helps handle complex systems by improving communication between developers and domain experts. But how do you apply it in practice? In this article, we explore the key concepts and strategies for effectively implementing DDD.

1. Understanding the Domain and Defining the Context

Before implementing DDD, it is essential to understand the business domain. Engage domain experts in the development process and use tools such as Event Storming and Domain Storytelling to map processes and identify key concepts.

Additionally, define Bounded Contexts, which set clear boundaries within the system to ensure that different parts of the software accurately reflect business concepts without overlap or inconsistencies.

2. Creating a Ubiquitous Language

One of the pillars of DDD is the Ubiquitous Language, which establishes a shared vocabulary between developers and stakeholders. This vocabulary reduces ambiguities and facilitates communication, ensuring that everyone involved speaks the same language when discussing the system.

To apply this in practice, document key terms, use them in the code, and avoid unnecessary technical jargon that could hinder understanding by business specialists.

3. Implementing Entities and Value Objects

When modeling the domain, use Entities and Value Objects to represent essential business concepts.

• Entities: have a unique identity and may change over time. Example: a purchase order identified by an ID.
• Value Objects: do not have their own identity and are immutable. Example: an address, which can be replaced but not modified.

Defining these structures correctly helps ensure a more robust design aligned with the business domain.

4. Applying Aggregates and Repositories

Aggregates group related entities under a single root to maintain system consistency. This prevents different parts of the software from modifying data in an uncontrolled manner.

Repositories, on the other hand, encapsulate the logic for persisting and retrieving Aggregates, keeping the domain decoupled from the infrastructure. Use patterns like the Repository Pattern to maintain a clear separation of concerns.

5. Using a Rich Domain Model and Domain Services

A common mistake is implementing an anemic model, where all business logic is placed in separate services rather than in entities. In DDD, a Rich Domain Model is encouraged, where business rules are applied within entities whenever possible.

When logic does not fit within an entity or Value Object, use Domain Services to encapsulate these operations, ensuring a clean and cohesive system design.

Conclusion

DDD is a powerful approach to handling complex domains and improving communication between development teams and stakeholders. By applying concepts such as Bounded Contexts, Ubiquitous Language, Entities and Value Objects, Aggregates, and Domain Services, it is possible to create a well-structured system aligned with business needs.

Although DDD requires an initial investment in learning and adaptation, its long-term benefits justify its application, making software development more efficient and sustainable.