~azzar1/unity/add-show-desktop-key

.. IVLE - Informatics Virtual Learning Environment

   Copyright (C) 2007-2009 The University of Melbourne

.. This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 2 of the License, or

   (at your option) any later version.

.. This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

.. You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

*********************

Architecture overview

*********************

This page describes the various subsystems of IVLE.

.. image:: /images/ivle-system-diagram.png

The IVLE web application

========================

User management server

======================

The "user management" server (:file:`usrmgt-server`) is an

inappropriately-named program which must be run as root in the background of

an IVLE instance. It is responsible for performing tasks at the request of the

IVLE web application, which require root privileges:

* Activating users when they first log into the system (including the creation

  of jails and user Subversion repositories).

* Creating group Subversion repositories.

* Rebuilding Subversion configuration files.

Subversion server

=================

User jails

==========

Scripts

=======

Database

========

Authentication

==============

There are two mechanisms by which IVLE can connect to an external server to

get information about users. These are typically used to connect to an

institution's central database to authenticate students, and download student

details (such as names and subject enrolment details).

Neither of these mechanisms are necessary; they are only useful where

third-party authentication is required.

.. _ref-auth-modules:

Auth modules

------------

IVLE's database contains user accounts, which includes a password (hash)

field. In this way, IVLE is fully-functioning without third-party

authentication modules. However, it is also often desirable to allow users to

log in without storing their password hash in the local database. IVLE allows

plug-in "auth modules" which can authenticate users with arbitrary logic, and

also create new user accounts.

This has at least the following two use cases:

* Allowing users to authenticate upon each login with a remote server. This

  allows users to log in without ever storing their password hash locally.

* Allowing users who have never used IVLE to log in, without an IVLE user

  account. Upon seeing an unknown username, an auth module can connect to a

  remote server, authenticate the unknown user, and create an IVLE user

  account on-the-fly, optionally downloading additional details (such as full

  name).

TODO: Describe how auth modules work.

.. _ref-subject-pulldown-modules:

Subject pulldown modules

------------------------

IVLE maintains lists of enrolled students in each subject, providing access to

worksheets and allowing submissions for enrolled users. Again, enrolments can

be made manually, but IVLE also allows plug-in "subject pulldown modules"

which can enrol students with arbitrary logic.

This allows a third-party server to dictate which IVLE users are enrolled in

which IVLE subjects.

Subject pulldown modules are used by the :program:`ivle-enrolallusers` script

to automatically enrol all existing users in subjects. Note that this does not

enrol users who are not in the IVLE database (perhaps because a third-party

auth module is being used to create user accounts on-the-fly, and some

students have not yet logged in for the first time).

Because of this, subject pulldown modules are also used whenever a student

logs in. This ensures that students who log in for the first time are

automatically enrolled in all subjects, according to the third-party server,

and also ensures that enrolments are kept up-to-date, should the third-party

server add new enrolments, or should new subjects be created in IVLE.

.. note::

   Enrolments are never removed by subject pulldown modules, only added.

   Students can only be un-enrolled from a subject by an administrator.

TODO: Describe how subject pulldown modules work.