Thank you for the reply.
As an example, suppose a resource is deleted, and -- as a side effect -- the relationship on a related resource is changed server-side. I am used to returning the related resource, containing an updated relationship that no longer contains the foreign key (or resource identifier, if you will) of the first resource.
There is no cascade -- only the first resource is deleted, and the relationship on the second resource is modified.
In this example, all that is changing (besides the deletion) is the relationship on the second, related resource. In my current paradigm, the only way to keep the client up-to-date is to return the related resource.
As a side note, I inspected the current Ember Data source, and it appears that the JSON serializer treats the response from a DELETE much in the same way as other methods. Thus, this perhaps less practical, and more a question about the JSON API specification.