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Domain Driven Design

Domain Driven Design: “What” not “How”

Many years have past since Eric Evans release the blue book: Domain Driven Design.  A lot has changed over the years but I find the core ideas still hold very true. In some ways, I think some of the concepts outlined are even more prevalent now than they have ever been. Ubiquitous Language The Ubiquitous Language is a shared language developed by the team.  The team is everyone working on the project: developers, domain experts, QA, BA. Everyone on the team. The ubiquitous language isn’t developed by the domain expert(s) alone.  If you have more than one domain expert, they may struggle with… Read More »Domain Driven Design: “What” not “How”

Clean up your Domain Model with Event Sourcing

I recently had a discussion with a developer who was new to Domain Driven Design, CQRS and Event Sourcing.  They were using Greg Young’s Simple CQRS Example to create there own simple app as learning exercise. After taking a quick look at their aggregate root, one thing that immediately stood out to me was a class field that contained current state.  Why this is interesting is because this field was not in any invariant. When I first started reading and exploring Event Sourcing, this was a big “ah ha!” moment for me. The realization that only certain data within my domain model was really important. We… Read More »Clean up your Domain Model with Event Sourcing

Bounded Context and Subdomains

In a previous blog, I discussed how I recently discovered through eventual consistency that I had poor business alignment.  With more thoughts and insights, I wanted to extend that post by discussion bounded contexts and how they fit within subdomains. 1 to 1? I’ve often thought of a bounded context as being a one-to-one relationship with a subdomain.   To take that further, you may get the impression that they are indeed the same thing.  When I was first introduced to the concept many years ago, I was under the impression that they mapped directly one to one. I’m not entirely… Read More »Bounded Context and Subdomains