I don't agree with equating cross cutting concerns with the purpose of "roles" in DCI. These are not mutually exclusive ideas. DCI is seems almost exclusively c

I don't agree with equating cross cutting concerns with the purpose of "roles" in DCI. These are not mutually exclusive ideas. DCI is seems almost exclusively concerned with changes in domain state. That is, organizing the interactions between actors in the domain model into contexts which, generally speaking, result in changes in state. I find, DCI doesn't say much with regards to how you query that state or present it to the user. I don't need a context or role to query data. Concerns do seem to provide some really nice ways to "DRY" things up on that end. Certainly you can use concerns to deal with interaction/role type issues, but then they really aren't all that "cross-cutting" they tend to be specific to a particular use case or scenario. In which case I think there are better options. DCI is one, domain services are another. But hey, if Concerns work as your golden hammer by all means. I have some doubts. I don't see this as a DCI vs. Concerns argument. However, if you want to argue it isn't possible to do DCI well in Ruby (extend sucks, yadda, yadda, yadda) go right ahead.