The idea is to use collections and items links for "defining" relations; but not for "resolving" them - at least not internally, and defining a full rest api is not particularly of interest in that setup.
To avoid diving into this and doing it wrong, i've set up something simple with element.parents and a write helper, that allows one to define how an element relates to others. As a toy model to full json schema.
Right now we're using some ad-hoc simple system. http://json-schema.org/latest/json-schema-hypermedia.html
The idea is to use collections and items links for "defining" relations; but not for "resolving" them - at least not internally, and defining a full rest api is not particularly of interest in that setup.