Link to operation mapping

Link stands for a relationship from one resource to the other, not an action between them, for example, from a book store resource to a book collection resource. With the relationship, the client actually can do more than one operations, i.e., get books (GET), add a book (POST), etc. Thus, link to operation is not one-one mapping, but one-to-many mapping.

In OAI’s Link Object, I see operationRef or operationId is a singular attribute. This seems like not fully comply with the link relation’s original intention.

[gentlewind]

@darrelmiller , thanks for your answering. It’s nice to define links independently and late bound to operations as link instances. The other use case that shall get benefits from this is, in a resource response, there could be multiple links with the same rel name. Some popular media types support this scenario. For instance, in HAL (hypertext application language), a link object’s key is the rel, and its value could either be a link object or an array of link objects. We would love to see this flexibility in OAI.

[handrews]

JSON Hyper-Schema allows multiple links with the same rel (it may be one of the few that does, apparently?) Our assumption is that, in terms of rel driving the semantics of the link, if you have multiple links with the same rel then they should be treated the same. There’s no clear mechanism of distinction that makes a lot of sense, or at least not that we’ve found so far.

You may end up using the target and/or context URI to distinguish them (or even target attributes like title, although I’d advise against using human-oriented fields for machine processing), but that doesn’t change the information imparted by rel.

Note that in draft-04, people used this to repeat links separately for each HTTP method. This was not the intended model and not the use case for the feature.