What is Domain Driven Design, Domain Driven Design, DDD

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What is Domain Driven Design?

Posted by Adrian M.

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Categories: Domain Modeling


Domain Driven Design (DDD) is not just a buzzword but a very important concept for business analysts and any technology practitioners involved in designing systems and software.  

Domain Driven Design is an approach to software design and architecture which, unsurprisingly, starts with an understanding of the problem domain for which the solution must be developed.   The DDD approach to software development and design focuses on creating software systems that closely align with and model the real-world domain they are intended to represent. 

The first step of Domain Driven Design  is to understand the problem domain and create an abstract model of the domain including its entities (nouns), functional (processes), business rules (logic/policies), and key goals and objectives.

There are three core principles of Domain Driven Design:

  • Focus on the core domain and domain logic - the practitioner must have a solid grasp of the problem domain and must have access to subject matter experts in the given domain
  • Design must be based on clear domain models - modeling the business domain is a top priority as it enables business experts to validate the practitioner’s understanding of the domain as well ensures corrections in that understanding
  • Based on ubiquitous language - the language used in the domain models must use language that the domain experts can read, understand, and verify. 

Deriving its roots from Object Oriented Analysis and Design (OOAD), the domain driven design approach relies on a number of interconnect concepts including:

  • Entities and Value Objects -  the DDD method distinguishes between entities and value objects. Entities are objects with a distinct identity that is defined by a unique identifier. Value objects, on the other hand, have no distinct identity and are defined solely by their attributes. 
  • Aggregates - An aggregate is a cluster of related entities and value objects that are treated as a single unit. Aggregates have a root entity that serves as the entry point for interacting with the cluster. Aggregates help maintain consistency and enforce business rules within a specific context.
  • Repositories - Repositories provide an abstraction layer for accessing domain objects, abstracting the underlying data storage and retrieval mechanisms. They enable the separation of domain logic from data access concerns.
  • Domain Services -  Domain services encapsulate domain-specific logic that doesn't naturally fit within an entity or value object. They are stateless and operate on domain objects to perform specific tasks.
  • Event Sourcing -  Event sourcing is a technique where changes to the state of a system are captured as a series of immutable events. This approach allows for reconstructing the system's state at any point in time and provides a historical record of all changes.
  • Domain Events -  Domain events are a way to capture and represent significant state changes within the domain. They can trigger actions in other parts of the system and help maintain consistency.

Domain Driven Design can greatly benefit business analysts by providing them with a structured framework for understanding, modeling, and communicating complex business domains. It encourages collaboration, clarity, and precision in requirements gathering and promotes the development of software systems that closely align with the real-world business needs.

Some of the ways in which domain driven design can help business analysts:

  • Shared Understanding - DDD encourages the use of a ubiquitous language that is shared between technical and non-technical team members. This common language ensures that everyone involved in the project has a clear and consistent understanding of the domain, its concepts, and its complexities.
  • Effective Communication - DDD encourages collaboration between business analysts and developers. By using the same domain terminology and concepts, business analysts can communicate requirements, constraints, and domain-specific knowledge more effectively to the development team.
  • Modeling Business Processes - DDD provides a framework for modeling business processes in a way that aligns with the domain's concepts and rules. This ensures that the resulting software accurately reflects the real-world business operations.
  • Identifying Domain Entities and Rules - The DDD approach  helps business analysts identify domain entities, their attributes, and the rules governing their behavior. This knowledge is essential for defining business requirements and constraints, as well as for ensuring that the software system enforces these rules correctly.
  • Bounded Contexts - This DDD concept helps business analysts define clear boundaries and contexts for different parts of the business domain. This ensures that each part of the system is designed to serve a specific purpose and that there is a clear understanding of where each boundary lies.
  • Event Modeling - DDD often involves event modeling, which is useful for capturing important state changes in the domain. Business analysts can help identify and prioritize domain events, as well as define how these events impact the business processes and data flow.
  • Requirements Elicitation - The DDD methodology encourages a deeper understanding of the domain, which can lead to more precise and well-informed requirements elicitation. Business analysts can leverage this understanding to gather and document requirements that align with the domain's intricacies.
  • User Story Definition - When defining user stories or use cases, business analysts can use DDD concepts to frame stories in the context of the domain. This ensures that user stories reflect the actual needs and goals of the business and that they are aligned with the domain model.



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Do your homework prior to the business analysis interview!

Having an idea of the type of questions you might be asked during a business analyst interview will not only give you confidence but it will also help you to formulate your thoughts and to be better prepared to answer the interview questions you might get during the interview for a business analyst position.  Of course, just memorizing a list of business analyst interview questions will not make you a great business analyst but it might just help you get that next job.



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