Domain-Driven Design (DDD) is an approach to software development that focuses on understanding and modeling the problem domain as a central aspect of the development process. It was introduced by Eric Evans in his book “Domain-Driven Design: Tackling Complexity in the Heart of Software.”
At its core, DDD encourages collaboration between technical experts (developers) and domain experts (those who understand the problem being solved) to create a shared understanding of the problem domain. Here are some key concepts in DDD:
- Ubiquitous Language: DDD promotes the use of a common language that is shared between developers and domain experts. This language should be used consistently in conversations, code, and documentation, helping to bridge the gap between technical and non-technical stakeholders.
- Bounded Contexts: Large and complex domains can be divided into smaller, more manageable chunks called bounded contexts. Each bounded context defines its own terms, concepts, and rules within a specific area of the domain. This helps to reduce complexity and enables teams to focus on specific parts of the system.
- Entities and Value Objects: DDD distinguishes between entities, which have a unique identity and are mutable, and value objects, which are immutable and defined solely by their attributes. These concepts help to model domain concepts more accurately and guide the design of the system.
- Aggregates: Aggregates define consistency boundaries within the domain, ensuring that changes to one part of the aggregate maintain consistency with other parts.
- Domain Events: Domain events represent meaningful occurrences within the domain that are relevant to the business. By capturing domain events, developers can model the behavior of the system more accurately and make it easier to understand the flow of data and processes.
- Repositories: Repositories provide a way to abstract the data access layer from the domain model. They encapsulate the logic for retrieving and storing domain objects, allowing the domain model to remain focused on business logic rather than infrastructure concerns.
Overall, DDD provides a set of principles and patterns for building complex software systems that are closely aligned with the problem domain. By focusing on the core concepts of the domain and using a common language shared between developers and domain experts, DDD aims to reduce complexity and improve the maintainability of software systems.