Domain Driven Design: Specification Question

Question

currently the system I am working on is layered like this

• Web UI
• Application
• Domain
• Infrastructure

In which layer would I put the specification implementations? Infrastrucutre?

Answer 1

Specifications are part of the Domain Model.

This pattern is described in Domain-Driven Design, and since this book deals explicitly with Domain Modeling, I think it's fair to say that it belongs in the Domain Layer.