In this context, a car is an aggregate of several other objects (the engine, the brakes, the headlights, etc.) Drivers do not have to individually control each wheel of a car, for instance: they simply drive the car. The aggregate root checks the consistency of changes in the aggregate. Objects outside the aggregate are allowed to hold references to the root but not to any other object of the aggregate. Models can be bound together by a root entity to become an aggregate. A domain event is an event that domain experts care about. Models can also define events (something that happens). When people exchange business cards, for instance, they only care about the information on the card (its attributes) rather than trying to distinguish between each unique card. In contrast, a value object is an immutable object that contains attributes but has no conceptual identity. As an example, most airlines assign a unique number to seats on every flight: this is the seat's identity. In domain-driven design, the domain layer is one of the common layers in an object-oriented multilayered architecture.ĭomain-driven design recognizes multiple kinds of models.įor example, an entity is an object defined not by its attributes, but its identity. These aspects of domain-driven design aim to foster ubiquitous language, meaning that the domain model should form a common language shared by domain experts for describing system requirements, business users, sponsors and developers. From this, developers build a domain model: a system of abstractions that describes selected aspects of a domain and can be used to solve problems related to that domain. A software's domain governs its context, the setting in which a word or statement appears that determines its meaning. Of primary importance is domain, the subject area to which the user applies a program is the domain of the software.
For example, if a software processes loan applications, it might have classes like LoanApplication and Customer, and methods such as AcceptOffer and Withdraw.ĭDD connects the implementation to an evolving model.
In terms of object-oriented programming it means that the structure and language of software code (class names, class methods, class variables) should match the business domain.
Full end-to-end coding examples demonstrate techniques for integrating a decomposed and distributed solution space while coding best practices and patterns advise you on how to architect applications for maintenance and scale.Domain-driven design ( DDD) is a software design approach focusing on modelling software to match a domain according to input from that domain's experts. You will learn how to build effective domain models through the use of tactical patterns and how to retain their integrity by applying the strategic patterns of DDD. A focus is placed on the principles and practices of decomposing a complex problem space as well as the implementation patterns and best practices for shaping a maintainable solution space. Methods for managing complex software construction following the practices, principles and patterns of Domain-Driven Design with code examples in C# This book presents the philosophy of Domain-Driven Design (DDD) in a down-to-earth and practical manner for experienced developers building applications for complex domains.