Actions vs. CRUD in REST

Question

Is it appropriate to perform actions with REST, other than simple create (POST), read (GET), update (PUT), and delete (DELETE)? I'm kind of new to the whole RESTful theology, so bear with me, but how should I accomplish the following:

• I have a web service that needs to talk to another web service. Web service A needs to "reserve" an object on Web service B. This object has a timeout of validity, but can be deleted immediately if need be. It's essentially a glorified permissions system which requires web services to reserve a space on web service B before taking any actions.

My initial thought was to 1. enable authentication of some sort, 2. in the serverside response to a GET call, reserve the space and return the result, and 3. provide immediate "unreservation" of the object via a DELETE call. Is this still being RESTful?

Answer 1

Yes, it's OK to perform actions with rest. What matters is that these actions should be guided by the representations you exchange.

If you think about the way the web works (via a browser), you do this all the time: you get an HTML form that lets you choose a number of actions you can perform. Then, you submit the form (typically via POST) and the action is performed.

It's good to be able to use DELETE via a programmatic client (which is something that non-AJAX requests in browsers wouldn't support), but the overall approach of a RESTful system should be very similar to what you find for websites (i.e. the focus should be on the representations: the equivalent of web pages in your system).

GET shouldn't have side effects, so don't use GET to make the reservation itself, use something like POST instead.