Finally, in our brief roundup of emerging JSON standards, we have HAL, which stands for Hypertext Application Language. Although filed as an Internet Engineering Task Force (IETF) Request For Comment (RFC), the last such submission was for version 8, which expired in May, 2016 (https://tools.ietf.org/html/draft-kelly-json-hal-08). As with JSON:API, HAL has its own accepted Content-Type header:

Content-Type: application/hal+json

The proposal is much like JSON:API. In contrast to JSON:API, however, the specification for hal+json has fewer mandatory (that is, required) keys, and more recommended (that is, should include) ones. As with JSON:API, hal+json includes provisions for a self-referencing JSON response, such that the client can retrieve the same information and learn where to go for further information. Furthermore, again as with JSON:API, there is provision for multiple responses and embedded documents within the response.

Here is an example based on the one shown...