On the Zend Framework blog there's a new post from project lead Matthew Weier O'Phinney covering REST representations in Expressive and the release of two new components to help with their implementation.
We've been working towards our various Apigility on Expressive goals, and have recently published two new components: zend-problem-details and zend-expressive-hal.
These two formats provide both JSON and XML representation options (the latter through a secondary proposal).
The post then goes on to talk about the idea of "representations" and how it relates back to the structure of the data returned and how the user knows what operations they can take on it. He also talks about the differences between normal responses and errors and gives example output helping to illustrate his points. The remainder of the post gets into the details of the two new components, their use and how to implement them in Expressive.