DDD Step By Step

DDD: Videos from Øredev

Leonard Petrica kindly pointed out that the videos from Øredev might be useful to those interested in Domain-Driven Design. They include talks from Jimmy Nilsson, Randy Stafford, Dan Berg Johnsson, Einar Landre and Eric Evans. So if you are interested...

Published Sun, Apr 26 2009 5:34 PM by Jak Charlton

Filed under: DDD

We Are Not Doing DDD

Recently I joined a new project, and within reason, and excluding some legacy systems we have to talk to, we have the “luxury” of an almost greenfield project. Probably as greenfield as you realistically get anyway. I was brought in partially as a good...

Published Wed, Apr 8 2009 7:36 PM by Jak Charlton

Filed under: DDD, Architecture, Services, Ubiquitous Language, Domain Experts

DDD: Invariants or Contextual Validation?

Greg Young made a good point to me regarding my last post about Validation, Consistency and Immutability , specifically around validation – even more specifically he thought I may have simplified it too far. I was trying to cover the basics of the subject...

Published Wed, Mar 11 2009 8:08 AM by Jak Charlton

Filed under: DDD, Architecture, Validation

DDD: Sample Application First Steps

As mentioned in my last post , the DDD Parcel Service is opening up for business soon. Also as mentioned, the first thing I did was to grab my Domain Expert and start some initial conversations around the first areas I am approaching – the Booking service...

Published Mon, Mar 9 2009 4:38 PM by Jak Charlton

Filed under: DDD, Domain Experts, Sample Code

DDD: The Beginning of My Sample Application

The Domain Driven Design Parcel Service is a small competitor in a hugely competitive market. With such competitors as UPS, FedEx and DHL, we are at a competitive disadvantage, and need a solution to cover our interactions with our customers, and to streamline...

Published Sat, Mar 7 2009 7:04 PM by Jak Charlton

Filed under: DDD, Architecture, Ubiquitous Language, Domain Experts, User Stories, Sample Code

DDD: Validity, Consistency and Immutability

There seems to be some confusion around these and similar concepts, so I thought it might be an idea to provide some clarification. Now these things aren’t specific to DDD, but they certainly have a lot of relevance there, and often provoke furious...

Published Wed, Mar 4 2009 11:39 AM by Jak Charlton

Filed under: DDD, Architecture, Validation

DDD: The Specification Pattern

Continuing our series on Domain Driven Design, we now get to one of the more interesting patterns in DDD – the Specification . A Specification is, in simple terms, a small piece of logic that sits on it’s own and gives an answer to a simple question ...

Published Mon, Mar 2 2009 10:55 AM by Jak Charlton

Filed under: DDD, Architecture, Double Dispatch, Specification

DDD: Living In The Enterprise

No, not that Enterprise! The other Enterprise – the big amorphous one that organisation spent a fortune putting SOA around. Domain Driven Design appears to be at odds with large scale distributed systems, it is after all methodology to design and...

Published Mon, Feb 23 2009 9:14 AM by Jak Charlton

Filed under: Distributed Systems, SOA, Enterprise

DDD: What Kind of Applications Is It Suited To?

In many conversations, and in many comments here, you hear phrases like “well that’s not really suited to DDD” or “DDD isn’t the best fit for that problem”. You even see those kind of comments on my blog, and often they are posted by me. This obviously...

Published Sun, Feb 22 2009 1:35 PM by Jak Charlton

Filed under: DDD, Architecture

DDD: The Repository Pattern

I seem to have taken a fairly long time to get here, and it has been mentioned in passing, but now we get to the last major part of the Domain Driven Design picture – Repository. In traditional architectures, your application talks to some kind of database...

Published Fri, Feb 20 2009 9:17 AM by Jak Charlton

Filed under: Repository, Persistence

DDD: Services

There can be no word more common in development, and no word used for such a multitude of different things as “service” It was therefore unfortunate that Eric Evans introduced yet another concept of Service in DDD, one which has since been referred to...

Published Wed, Feb 18 2009 1:35 PM by Jak Charlton

Filed under: Services, Domain Services

DDD: Aggregates and Aggregate Roots

We are family I got all my sisters with me Sister Sledge Some things belong together, like Apple Pie and Ice Cream, or Sonny and Cher. And so it is with Entities and Value Objects (VOs) – some of them belong together. Aggregates are groups of things that...

Published Mon, Feb 16 2009 3:49 PM by Jak Charlton

Filed under: DDD, Aggregate

DDD: Entities and Value Objects

Finally, after 5 posts in the series, we get to the beginning point, the basis of all things… Entities and Value Objects. OK, maybe a small exaggeration, but Entities and Value Objects (VO) form the core building blocks of Domain Driven applications....

Published Sat, Feb 14 2009 3:53 PM by Jak Charlton

Filed under: DDD, Value Objects, Entities

DDD : Command Query Separation as an Architectural Concept

There has been some confusion recently around a recent evolution of DDD, the idea of Command Query Separation (CQS) at the architectural level. This post is yet again jumping ahead into the “advanced” stuff, so go ahead and skip this if you just want...

Published Fri, Feb 13 2009 3:42 PM by Jak Charlton

Filed under: DDD, Architecture, SOA, Enterprise, Persistence, Bounded Context

DDD: There Is No Database

Do not try to bend the spoon; that's impossible. Instead only try to realize the truth: There is no spoon. The Matrix Again prompted by discussion on the DDD Yahoo list, this post is intended to explain what on the face of it is a pretty dumb assertion...

Published Thu, Feb 12 2009 3:37 PM by Jak Charlton

Filed under: DDD, Persistence

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