What kind of Webservice-Communication-Technologies are available?

Question

I try to make a list of the available web service com techniques and what they're specially good for (pros and cons).

I know:

XML: One way (client asks server for data)

XML-RPC: Bidirectional (client can command server, get data, send data)

Hessian: Very fast because binary form? Better for images, not good for text? Not sure?

What else?

Answer 1

I've used REST based services using JSON. I've used the following open source code:

Kosmaczewski's REST wrapper although most now prefer ASIHTTPRequest - for making the HTTP calls TouchJSON for serializing request/response dictionaries to/from JSON

A search for iPhone REST on SO also turns up a lot of useful answered questions