Hi,
a little update about web services in Moodle 2.2:
Moodle 2.2 will come with many web service improvements. Most of them have already been integrated: MDL-29276
The major ones are:
* the web service developer documentation is less wordy and more code oriented: http://docs.moodle.org/dev/Web_services
* the web service user documentation has been reduced too: http://docs.moodle.org/20/en/Web_services
* more code examples supporting the documentation: demo clients and thrid party web service function template
* SOAP and XML-RPC servers return clear error messages when Moodle debug mode >= NORMAL
* any error at the web service description level is clearly indicated => which parameter/returned value is wrong, and what was expected.
* REST server can return JSON too.
* Web service naming convention is clearly defined
* An API Roadmap is available: http://docs.moodle.org/dev/Web_services_Roadmap