What is Domain Driven Design?

Question

Can somebody please explain (in succinct terms) what exactly is domain driven design? I see the term quite a lot but really don\'t understand what it is or what it looks like. H

Answer 1

As in TDD & BDD you/ team focus the most on test and behavior of the system than code implementation.

Similar way when system analyst, product owner, development team and ofcourse the code - entities/ classes, variables, functions, user interfaces processes communicate using the same language, its called Domain Driven Design

DDD is a thought process. When modeling a design of software you need to keep business domain/process in the center of attention rather than data structures, data flows, technology, internal and external dependencies.

There are many approaches to model systerm using DDD

• event sourcing (using events as a single source of truth)
• relational databases
• graph databases
• using functional languages

Domain object:

In very naive words, an object which

• has name based on business process/flow
• has complete control on its internal state i.e exposes methods to manipulate state.
• always fulfill all business invariants/business rules in context of its use.
• follows single responsibility principle

Answer 2

Here is another good article that you may check out on Domain Driven Design. if your application is anything serious than college assignment. The basic premise is structure everything around your entities and have a strong domain model. Differentiate between services that provide infrastructure related things (like sending email, persisting data) and services that actually do things that are your core business requirments.

Hope that helps.

Answer 3

DDD(domain driven design) is a useful concept for analyse of requirements of a project and handling the complexity of these requirements.Before that people were analysing these requirements with considering the relationships between classes and tables and in fact their design were based on database tables relationships it is not old but it has some problems:

• In big projects with complex requirements it is not useful although this is a great way of design for small projects.

• when you are dealing with none technical persons that they don,t have technical concept, this conflict may cause some huge problems in our project.

So DDD handle the first problem with considering the main project as a Domain and splitting each part of this project to small pieces which we are famous to Bounded Context and each of them do not have any influence on other pieces. And the second problem has been solved with a ubiquitous language which is a common language between technical team members and Product owners which are not technical but have enough knowledge about their requirements

Generally the simple definition for Domain is the main project that makes money for the owners and other teams.

Answer 4

EDIT:

As this seem to be a top result on Google and my answer below is not, please refer to this much better answer:

https://stackoverflow.com/a/1222488/1240557

OLD ANSWER (not so complete :))

In order to create good software, you have to know what that software is all about. You cannot create a banking software system unless you have a good understanding of what banking is all about, one must understand the domain of banking.

From: Domain Driven Design by Eric Evans.

This book does a pretty good job of describing DDD.

Register to download a summary of the book, or download the summary directly.

Answer 5

You CAN ONLY understand Domain driven design by first comprehending what the following are:

What is a domain?

The field for which a system is built. Airport management, insurance sales, coffee shops, orbital flight, you name it.

It's not unusual for an application to span several different domains. For example, an online retail system might be working in the domains of shipping (picking appropriate ways to deliver, depending on items and destination), pricing (including promotions and user-specific pricing by, say, location), and recommendations (calculating related products by purchase history).

What is a model?

"A useful approximation to the problem at hand." -- Gerry Sussman

An Employee class is not a real employee. It models a real employee. We know that the model does not capture everything about real employees, and that's not the point of it. It's only meant to capture what we are interested in for the current context.

Different domains may be interested in different ways to model the same thing. For example, the salary department and the human resources department may model employees in different ways.

What is a domain model?

A model for a domain.

What is Domain-Driven Design (DDD)?

It is a development approach that deeply values the domain model and connects it to the implementation. DDD was coined and initially developed by Eric Evans.

Culled from here

Answer 6

I believe the following pdf will give you the bigger picture. Domain Driven Design by Eric Evans

NOTE: Think of a project you can work on, apply the little things you understood and see best practices. It will help you to grow your ability to the micro service architecture design approach too.