HTML Forms can declare a method, the HTTP verb that is used when the form is submitted, the value of this method is GET or POST.
The HTML5 spec briefly had PUT and DELETE as valid methods for the form method but has now removed them. Firefox also added support and subsequently removed them.
Recently over the course of Brexit night at The Guardian we got into a discussion about why this was the case and what the “right” way to map a form into a REST-like resource system would be.
The first piece of research was to dig into why the additional methods had been added and then removed. The answer (via Ian Hickson) was simple: PUT and DELETE have implied idempotency, the nature of form submission is that it is inherently uncacheable and therefore cannot be properly mapped onto those verbs.
So, basic problem solved, it also implies the solution for the url design for a form. A form submission represents a user submitting an untrusted data payload to a resource, this resource in turn choose to make PUT or DELETE requests but it would be dangerous to have the form do this directly.
The resource therefore is one that represents the form submission. In terms of modelling the URL I would be tempted to say that it takes the form
:entity/form/submission, so for example:
There may be an argument that POSTing to the form resource represents submission so the submission part of the structure is unnecessary. In my imagination though the form resource itself represents the metadata of the form while the submission is the resource that essentially models a valid sumbission and the resource that represents the outcome of the submission.