Aug
12
2010
0

Value objects are only just playing a role

Recently I had an interesting discussion on the DDD mailing list about value objects.

Value objects: “These are the objects that describe things” [From: DDD, Evans]

The discussion centered on the immutability of value objects. The strange thing is that many developers (in the role a modeller) emphasize this immutability. I’ve seen this happen quite often. While I do not think that is the essence of a value object at all. read more…

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Jul
15
2010
0

No Exceptions made

In response to a finding during an internal project code review last Friday and an article in the latest Java Magazine we had an interesting discussion on the reasons for using exceptions. Eventually I supported two rules of thumb, one I had thought of myself, the other from a colleague of mine.

The following rules of thumb should be seen as in the context of a development platform that supports their use and a developer who uses as the following, basic rule for recognizing the situation to use an exception: use an exception if you cannot follow the normal execution path any more, in other words, if something extraordinary happens or has happened. read more…

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Mar
10
2010
4

CQRS & the architecture coming along

In my previous blog post I made a proposal in the footnotes to rename the architecture that often comes along with the pattern CQRS. I thought of a “Circular Architecture” to clearly contrast it with a “Layered Architecture”. After a brief discussion with Greg Young and Alistair Cockburn about this I decided to take this idea under the microscope. They both claimed that the “Hexagonal Architecture” describes this architecture sufficiently. That got me thinking, since I respect both their opinions very much. First some definitions.

read more…

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Mar
04
2010
0

CQRS && Validation && Business Rules

Validation and business rules within a CQRS architecture [1][2] continue to raise issues for those who first hear of it. Three specific questions are often asked: how does the validation of commands work, how can one enforce business rules on large collections (state) and how does the enforcement of business rules on multiple aggregates work? Hopefully I can help some readers with my three replies. First the questions. read more…

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Mar
12
2009
0

Seminar Fixed price + Agile + DDD

During the evening of March the 17th, Sogyo will organize another technical seminar. In this one, Sogyo employees Rick van der Arend (that’s me!) and André Boonzaaijer will explain how we can handle the wishes of many of our customers to get an agile software project, in a domain driven way, but with a planned and fixed budget.

Experiences they have had in several recent projects will play a central role. Workshop techniques and several other activities you should undertake during the domain exploration phase will be presented. Next to that, Rick and André will answer the question: how do you fill and estimate the SCRUM product backlog up front? In short, this will be an interesting evening.

The seminar starts at 18:00 with a bite to eat and at about 19:00, Rick and André will start their intro. The program will last until about 22:00. Sogyo employees can subcribe to the seminar by sending an e-mail to marketing@sogyo.nl. If you are not a Sogyo employee, but you are interested in this seminar, please e-mail Anneke van Beek at avbeek@sogyo.nl

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Feb
20
2009
0

Domain exploration – really

The last few week have been quite exhilirating! Two weeks of really exploring a domain, getting to know a new client’s business and language. I have always liked going through such a phase and one does not always get the chance to do something like that for two whole weeks at the client’s site. read more…

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