The API should be organized around resources. As mentioned earlier, resources are the key abstraction of information so a service makes them available to its clients. The internal structure of a resource should not leak through the APIs. For example, the details of an order might be stored separately in a relational database, so we should not create multiple resources to mirror that internal structure. APIs should focus on business entities and use resources as the abstraction to hide implementation details, making the API implementation evolvable.