the thing was that Jose needed to know the package_id of a given package instance for a given community_id, so with having the community_id you can get the url of it, and then joining url + the package-key to form the full url for the specific application instance, and then, with that full url using site_node::get to get the package_id.
i.e.
../classA/ (we know the community_id)
../classA/evaluation (we want to know the package_id for the evaluation instance)
solution: site_node::get -url "../classA/evaluation" will return among other things, the package_id
=)
