by Malte Reißig.
hey asha,
while "waiting for a reply" I can recommend you to go through http://docs.moodle.org/27/en/How_to_create_and_enable_a_web_service again.
As well have a look at the dialog on this page here, where jerome said:
> Hi Jackie,
Here is what I think about that: To enable this kind of "token authentication" you need to set your "External service"-Configuration to "Required capability set". Then your moodle webservice knows and checks the capabilities and roles of each requesting user through the wstoken you send.
For more infos on working with roles and capabilities in moodle please check the link in one of jeromes answers above.
Hope this helps + Cheers!