# Khalil Stemmler - An Introduction to Domain-Driven Design (DDD) (Highlights) ![rw-book-cover|256](https://khalilstemmler.com/img/blog/ddd-intro/ddd-intro.png) ## Highlights - Because Domain Services are a part of the **Domain Layer** and adhere to the [dependency rule](https://khalilstemmler.com/wiki/dependency-rule/), Domain Services aren't allowed to depend on infrastructure layer concerns like [Repositories](https://khalilstemmler.com/articles/typescript-domain-driven-design/repository-dto-mapper/) to get access to the domain entities that they interact with. Application Services fetch the necessary entities, then pass them to domain services to run allow them to interact. ([View Highlight](https://read.readwise.io/read/01kzfkajxtgsgwpnvjhm442ta3)) ^1041907562