Domain Driven Design - What is it and why

What is DDD?

In very simple terms DDD is about making your software as a model of a real world system or a process. When practicing DDD you'll work with a domain expert to build a ubiquitous language (UL). UL is a conceptual description of the system. UL is written down in such a way that domain expert should be able to understand and verify the UL is correct.

UL will include words that is used in actual domain. UL forms the basis of the OO design. DDD will have  following object categories

• Value objects
• Entities
• Aggregate roots 

Recommended patterns for DDD

• Repository 
• Factory
• Service

When not to use DDD (airbrake)

DDD is not suitable for projects where requirements and domain expertise is less. DDD sometimes goes in as an iteration which may not be suited for some projects. It may not be suited for projects which involves high technical complexity as opposed to domain complexity as well. 

Thoughtworks - Designing Domain driven design service architecture

Also see Clean Domain Driven Design

Notes

https://stackoverflow.com/questions/1222392/can-someone-explain-domain-driven-design-ddd-in-plain-english-please/1222488#1222488

https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/microservice-ddd-cqrs-patterns/ddd-oriented-microservice

https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/microservice-ddd-cqrs-patterns/net-core-microservice-domain-model

https://hackernoon.com/clean-domain-driven-design-in-10-minutes-6037a59c8b7b