CodEagle

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.

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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…