Domain-driven design (DDD) is an approach to develop software for complex needs by connecting the implementation to an evolving model.

learn more… | top users | synonyms (1)

6
votes
1answer
1k views

Unique Value Object vs Entity

Trying to convert some entities into value objects I am stuck in a case where what seems a value object must be unique within an aggregate. Suppose we have a Movie entity which makes the root of an ...
6
votes
1answer
354 views

DDD: service contains two repository

Does it correct way to have two repository inside one service and will it be an application or domain service? Suppose I have a Passenger object that should contains Passport (government id) object. ...
6
votes
2answers
324 views

Avoiding ubiquitous language clashes

I have been reading DDD Quickly and wondered about how to avoid naming clashes with technical terms and domain terms. For example, if I commonly used the repository pattern (with classes such as ...
6
votes
3answers
529 views

Resources for popular domain models [closed]

I have come across many situations where I had to build a system for a library or a clinic or other popular domains. The thing is a domain model for a library was probably done 1000 times already with ...
6
votes
2answers
1k views

Are Persistence-Ignorant objects able to implement lazy loading?

Persistence Ignorance is an application of single responsibility principle, which in practice means that Domain Objects (DO) shouldn't contain code related to persistence, instead they should only ...
6
votes
2answers
649 views

DDD: Can immutable objects also be entities?

I've read countless posts on differences between Entities and Value objects and while I do think that at least conceptually I understand how the two differ, it appears that in some of these posts ...
6
votes
2answers
1k views

Unit Test Friendly Domain Driven Design

Many of the readings I've done on DDD, both in books and online, seem to represent code that, often times, is difficult or impossible to unit test. For example, there are numerous samples with static ...
6
votes
1answer
179 views

DDD Architecture in a MVC web application

I am putting together a web application using DDD however am strugleing to put the text book DDD model into a real world MVC application. I currently have these layers: Controllers > ...
6
votes
3answers
385 views

In domain driven design, how do I convert a database table with a primary key into a Value Object?

Lets suppose there's a database schema defined like this: Person.mail_address_key ----- Address.address_key Person.billing_address_key ----- Address.address_key A Person has a mailing address and a ...
6
votes
2answers
451 views

DDD / Layers and legacy systems

I have to refactor a complex C# app (many dialogs, mixed logic and so on). There is a part managing the communication with special hardware equipments (sending commands and receive data via ...
6
votes
1answer
538 views

To Repository Or Not To Repository

When I first learnt about Domain Driven Design, I was also introduced to the repository and unit of work patterns that once seemed to be top notch for the cool kids that threw SQL queries like ...
6
votes
3answers
3k views

Inject dependency as method parameter instead of constructor parameter

I'm using an ORM which doesn't allow me to inject dependencies in the constructor. Let's say I'm using DDD for the business logic, and the MVC pattern for the UI. Now one of my domain objects needs ...
6
votes
3answers
1k views

Duplication in parallel inheritance hierarchies

Using an OO language with static typing (like Java), what are good ways to represent the following model invariant without large amounts of duplication. I have two (actually multiple) flavours of the ...
5
votes
6answers
548 views

Should a domain expert make class diagrams?

The domain expert in our team uses UML class diagrams to model the domain model. As a result, the class diagrams are more of technical models rather than domain models (it serves of some sort of ...
5
votes
3answers
2k views

DDD - Aggregate Roots - Dealing with Efficiency and Concurrency

First off, I'll admit that I'm a newbie to DDD and need to read the "blue book". I'm building a system that has an AggregateRoot of type "Match". Each Match can have a collection of "Votes" and also ...
5
votes
6answers
252 views

In a team practicing Domain Driven Design, should the whole team participate in Stakeholder meetings?

In my experience, a Software Development Team that comprises: 1 Project Manager 1 Tech Lead 1 - 2 Senior Dev 2 - 3 Junior Dev (Fresh grad) Only the Tech Lead & PM (and/or Senor Dev/s) will ...
5
votes
3answers
323 views

Model relationships with DDD (or with sense)?

Here is a simplified requirement: User creates a Question with multiple Answers. Question must have at least one Answer. Clarification: think Question and Answer as in a test: there is one ...
5
votes
2answers
2k views

Do we achieve 100% Persistence Ignorance solution if we're not using ORM's POCO objects to model the Domain?

Persistence ignorance is ability to retrieve/persist standard objects, where standard objects are considered as classes focused on particular business problem and thus don't contain any ...
5
votes
2answers
87 views

Where should business logic go in a layered architecture?

First of all, i'm not talking about validation in the sense of the nullability or length of a field like in this and this questions where we can use isValid() methods in business classes or an ...
5
votes
2answers
2k views

Should I use an aggregate root when designing my repository?

I have an entity that is called Master which is composed of a number of Slave entities. There can only be one Master in my database and I want to query repositories to get the Slave for a given id. ...
5
votes
4answers
1k views

Refactoring jQuery spaghetti code to use DDD [closed]

Most of my client side code ends up as a long script in one file the mostly looks like this: <script> function someFunction1(){/*...*/} function someFunction2(){/*...*/} ... var ...
5
votes
3answers
796 views

Good practices to implement mappers in a multi-tier application

When you are working with a multi-tier application very often you run into task of converting objects in one layer to objects in another layer. This could be converting database objects into domain ...
5
votes
1answer
197 views

“Implementing DDD” by Vernon: value object or not?

On page 382 of this book there is a passage talking about using value objects in aggregates, under the (entity) root. There is an example of Product that, besides other values, contains a ...
4
votes
5answers
799 views

How to model an address type in DDD?

I have an User entity that has a Set of Address where Address is a value object: class User{ ... private Set<Address> addresses; ... public setAddresses(Set<Address> ...
4
votes
2answers
2k views

Equivalent of Domain Driven Design for functional programming languages

I really love the idea of domain driven design, however, as I'm learning Go, I'm wondering if there's the equivalent of DDD that's aimed at an effectively more functional language?
4
votes
1answer
301 views

Tools to support learning a new business domain [closed]

Suppose you just accepted a job, writing code in an industry sector that you've never worked in before. To be effective, you want to immerse yourself in the business domain - to understand the ...
4
votes
3answers
621 views

Scrum, DDD, and front-end development in an enterprise environment

So, I've been working for a bank for the past 4 years. My main responsibility has been online banking. Over the past year, we've been implementing the scrum methodology. We've also changed to domain ...
4
votes
4answers
398 views

Data access for composable applications

I'm wondering if anyone can share their thoughts, experience and guidance on how to approach the data access layer for a composable application? By composable application, I mean an application with ...
4
votes
3answers
2k views

DDD and Value Objects. Are mutable Value Objects a good candidate for Non Aggr. Root Entity?

Here is a little problem Have an entity, with a value object. Not a problem. I replace a value object for a new one, then nhibernate inserts the new value and orphan the old one, then deletes it. Ok, ...
4
votes
1answer
790 views

How to deal with queries that do not return full entities in Domain Driven Design?

In my application, I have a listing of information that is deducted from a query that combines information from several entities. In itself, a very common situation. Now, the corresponding repository ...
4
votes
2answers
846 views

Encapsulation in Domain Driven Design models?

I am using EF Code First and I had a model like below. public class Account { [Required] public string AccountNo { get; set; } [Required] public decimal Balance { get; set; } } I ...
4
votes
1answer
509 views

Is it Ok if Domain Object cross Service Boundary

Is it Ok if Domain Object cross Service-Boundary? Everyone recommend that only DTO should be returned by Services. I am creating simple CRUD application. Is it ok if my service methods return ...
4
votes
2answers
2k views

DDD – A rookie’s unanswered questions

I’ve decided to use DDD in one of my pet projects to find out what the fuss is about! Let me start off by saying that this (DDD) is the way software SHOULD be written, I’ve seen some strange patterns ...
4
votes
2answers
212 views

Is this too much work for a Gateway to do?

I'm writing a Gateway class that wraps access to a web service which provides information about a player's item inventory in a video game. This web service returns a variety of information, however I ...
4
votes
4answers
294 views

How to decide whether to implement an operation as Entity operation vs Service operation in Domain Driven Design?

I am reading Evans's Domain Driven Design. The book says that there are entity and there are services. If I were to implement an operation, how to decide whether I should add it as a method on an ...
4
votes
1answer
281 views

Should I be using separate 'domain' layer?

I have been reading a lot about domain layer and DDD. However I am still confused about it. To me they seem to be a fancy name for business classes however more modelled towards your application ...
4
votes
3answers
746 views

DDD, modularizing the application and domain layers without breaking the DIP

Quoting DDD theory: The application layer is thin in terms of domain logic - it merely coordinates the domain layer objects to perform the actual work. When it comes to modularization, and ...
4
votes
2answers
373 views

How should I include third-party models in my domain model?

I'm currently trying to design a little application using Domain Driven Design but I'm afraid I don't really get the concept yet. Let me try to explain this as clearly as possible. public interface ...
4
votes
2answers
403 views

How to define the seams between the domain layer and a database full of stored procedures?

We have a legacy database full of stored procedures. These stored procedures are somewhat CRUD-categorized but upon inspection of some procedures, they are not "simple" as they might update, delete, ...
4
votes
1answer
69 views

DDD – duplicity between Aggregates – should I use one table?

I understand that there exists duplicity of data between Bounded Contexts. The thing is that I'm not really sure about duplicity of data between Aggregate roots. Example: I have product in Product ...
4
votes
3answers
420 views

Architecting multi-model multi-DB ASP.NET MVC solution

I have an ASP.NET MVC 4 solution that I'm putting together, leveraging IoC and the repository pattern using Entity Framework 5. I have a new requirement to be able to pull data from a second database ...
4
votes
2answers
447 views

A design decision in composition or aggregation

I've recently had doubts about some design decisions that I frequently make, so this time I decided to take some time and try to analyze it to find the best solution. I will describe a simple scenario ...
4
votes
2answers
762 views

Justification for bidirectional relationship

I typically try and avoid bidirectional relationships at all costs. Recently I've been trying to follow a more domain centric design philosophy and I'm looking for advice in the best way to solve a ...
4
votes
2answers
448 views

Domain Objects with Interfaces

I'm in a situation where part of my system has a dependency on another module in the same system, but the modules themselves need to remain independently deployable, where the parts they depend on ...
4
votes
2answers
254 views

When is it appropriate to map a DTO back to its Entity counterpart

From what I've read and implemented, DTO is the object that hold a subset of value from a Data model, in most cases these are immutable objects. What about the case where I need to pass either new ...
4
votes
1answer
245 views

What and how much domain code should be put in an F# module

According to recommendations given here, F# modules should correspond to DDD bounded contexts, i.e. subdivisions of a business domain. The bounded context I'm working on right now has 2 aggregates ...
4
votes
5answers
547 views

Is DDD not appropriate for my website or should I introduce a Query Layer?

I have inherited an ASP.NET website application and the previous developer has used what I believe are some DDD concepts. I am new to DDD and I have to admit I am struggling with the practical side of ...
4
votes
1answer
1k views

DDD: Domain Model Factory Design

I am trying to understand how and where to implement domain model factories. I have included my Company aggregate as a demo of how I have done it. I have included my design decisions at the end - I ...
4
votes
1answer
206 views

OOP, domain models, and the user

When developing domain models, I can see two major ways of thinking about the user: The first one assumes that a program is a kind of "simulation" of what happens in the real world, and the user is ...
4
votes
3answers
689 views

Ensuring transactional consistency with DDD

I am starting out with DDD and understand that aggregate roots are used to ensure transnational consistency. We should not modify multiple aggregates in one application service. I would like to know ...