DDD: How to Identify Domain Entities
As a web developer, you may have encountered the concept of objects and data structures in your work. However, when it comes to Domain-Driven Design (DDD), it’s essential to think about entities in a different way. In this post, we’ll share some tips on how to identify domain entities in your web development project.
In DDD, an entity is a unique thing that is distinguishable from other things. It has a unique identity that sets it apart from others. Unlike a data structure, which is simply a way of organizing data, an entity is a specific thing with a distinct identity.
To understand entities better, let’s consider a simple example. Imagine that you’re building a web application for a library. In this case, some of the entities that you might identify are:
Books: Books have a unique ISBN or identifier that distinguishes them from other books. They have a title, author, and other attributes that define them as individual entities.
Users: Users of the library have a unique identifier such as a library card number that distinguishes them from other users. They have attributes such as name, address, and other information that define them as individual entities.
Loans: Loans represent the transaction where a user borrows a book from the library. A loan has a unique identifier such as a loan number, and it has a due date, loan date, and other attributes that define it as an individual entity.
Once you’ve identified entities in your application, you can use them to build a domain model that accurately reflects the business domain. For example, in our library application, we might build a domain model that represents the relationships between books, users, and loans.
In conclusion, identifying domain entities is crucial to applying Domain-Driven Design to web development. By gaining a thorough understanding of the business domain, looking for unique identities, considering the lifecycle of the entity, and analyzing relationships, you can identify entities that are important to the business and build a domain model that accurately reflects them. This can help you build software that meets business requirements and is easier to maintain over time.
