Domain-Driven Design (DDD) Overview

The Domain-Driven Design (DDD) is a set of principles for software projects conceptualized by Eric Evans and formalized in his 2003 book of the same name.

Key Principles of DDD

Focus on Core Domain and Domain Logic

• DDD emphasizes the central objective of developing systems with a design centered around concepts closely aligned with the complexities and nuances of the problem domain, rather than merely addressing technical challenges.

Understanding the Domain

• The domain of a system encompasses the business area and problem it aims to solve.
• DDD advocates for developers to possess a deep understanding of the system's domain, acquired through frequent conversations with domain experts. The system's design should align with the domain rather than conforming to specific programming technologies.

Separation of Domain and Technology DDD promotes the separation of domain and technology, expressed in the system's architecture. Architectural patterns such as Layered Architecture, Clean Architecture, or Hexagonal Architecture can be employed for this purpose.

Ubiquitous Language is a key concept in DDD, involving a set of terms that must be fully understood by both domain experts and the development team (programmers, QA, UX). Successful software projects require a shared language between domain experts and developers, constituting the Ubiquitous Language of the system.

Bounded Contexts represent logical boundaries within which a specific domain model is defined, and business rules are consistently applied. Each delimited context is autonomous and independent, allowing for better organization and code scalability.

Within a bounded context, entities, aggregates, services, and business rules relevant to that specific domain are defined. Clear definition of context boundaries is crucial to avoid conflicts and ambiguities in the code.

Setup

Follow these steps to set up the project:

1. Clone the Repository:

   git clone git@github.com:flaviomdutra/ddd-nodejs.git

2. Install Dependencies: We are using PNPM for package management. If you haven't installed it yet, you can do so with npm install -g pnpm. After that, you can install the dependencies with:

   pnpm install

Applicability

When to Apply DDD

• DDD is particularly beneficial in systems with complex domains, where business rules are challenging to grasp immediately and intricate for developers to implement.
• DDD is also useful in projects with a large development team, where a shared language is essential to ensure everyone is on the same page.
• DDD is also recommended for projects with a long lifespan, where the domain is likely to evolve over time.

When Not to Apply DDD

• DDD is not recommended for simple systems with a straightforward domain, where the business rules are easy to understand and implement.
• DDD is also not recommended for projects with a small development team, where a shared language is not as crucial.
• DDD is also not recommended for projects with a short lifespan, where the domain is unlikely to evolve over time.