I try to use RPC with JavaScript on a public website without a login. I tried this (just to test and show you what I did):

var session = new openerp.Session();
var suchmodel = new openerp.Model(session, 'such.model');
suchmodel .call('such.function', [suchvalue])
    .then(function (result) {
        console.log('then');
        console.dir(result);
    })
    .fail(function (result) {
        console.log('fail');
        console.dir(result);
    });

The fail function is called and the result.data.debug contains this error message:

Traceback (most recent call last):
  File "/var/www/openerp/http.py", line 532, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/var/www/openerp/addons/base/ir/ir_http.py", line 151, in _dispatch
    auth_method = self._authenticate(func.routing["auth"])
  File "/var/www/openerp/addons/base/ir/ir_http.py", line 92, in _authenticate
    getattr(self, "_auth_method_%s" % auth_method)()
  File "/var/www/openerp/addons/base/ir/ir_http.py", line 69, in _auth_method_user
    raise http.SessionExpiredException("Session expired")
SessionExpiredException: Session expired

I tried to use openerp.session but this is empty.

Is it possible to do this calls without a login?