[sujeetsr]

But what this doesn't say is, how do I get the structure of the data that I should post to a RESTful resource? For example, in level 3, with a starting uri of /doctors/mjones/slots?date=20100104&status=open, I get back two additional uris of the two slots, and if I want to book one, I send a POST to /slots/1234, with an xml structure containing the patient id. So, to be a completely discoverable api, shouldnt the response also tell me what the xml structure should look like?

When you look at a wsdl file, it tells you both where the service is located, as well as the structure of the data that one must send to it. I haven't been able to find an equivalent for the second part in the REST world. Anyone know?

[blasdel]

The API should take as input the same structure it gives in responses.

Ideally you would get different kinds of responses for the same resource by using the Accept header, so that browsers get text/html but your app gets application/xml or whatever you asked for. Unfortunately everyone seems to be following Rails' lead of just appending extensions onto the end of URLs — if you're lucky they'll use HATEOAS, but they usually just expect you to concatenate strings on your end using foreknowledge.