REST: HTTP headers or request parameters

Question

I've been putting in some research around REST. I noticed that the Amazon S3 API uses mainly http headers for their REST interface. This was a surprise to me, since I assumed that the interface would work mainly off request parameters.

My question is this: Should I develop my REST interface using mainly http headers, or should I be using request parameters?

Answer 1

The question mainly is whether the parameters defined are part of the resource identifier (URI) or not. if so, then you would use the request parameters otherwise HTTP custom headers. For example, passing the id of the album in a music gallery must be part of the URI.

Remember, for example /employee/id/45 (Or /employee?id=45, REST does not have a prejudice against query string parameters or for clean slash separated URIs) identifies one resource. Now you could use content-negotiation by sending request header content-type: text/plain or content-type: image/jpg to get the info or the image. In this respect, resource is deemed to be the same and header only used to define format of the resource.

Generally, I am not a big fan of HTTP custom headers. This usually assumes the client to have a prior knowledge of the server implementation (not discoverable through natural HTTP means, i.e. hypermedia) which always is considered a REST anti-pattern

HTTP headers usually define aspects of HTTP orthogonal to what is to be achieved in the process of request/response. Authorization header (really a misnomer, should have been authentication) is a classic example.