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<title>Moodle Docs: Developers Manual</title>
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<h2>Developers Manual</h2>
<p>This document describes some of Moodle's design and how you can contribute.</p>
<p>Sections in this document:</p>
<li><a href="#architecture">Moodle architecture</a></li>
<li><a href="#contribute">How you can contribute</a>
<li><a href="#activities">Learning activities</a></li>
<li><a href="#themes">Themes</a></li>
<li><a href="#languages">Languages</a></li>
<li><a href="#database">Database Schemas</a></li>
<li><a href="#courseformats">Course formats</a></li>
<li><a href="#doc">Documentation and articles</a></li>
<li><a href="#bugs">Participating in the bug tracker</a></li>
<h3><a name="architecture"></a>1. Moodle architecture</h3>
<p>From a system administrator's perspective, Moodle has been designed according
to the following criteria:</p>
<li><strong>Moodle should run on the widest variety of platforms</strong><br>
The web application platform that runs on most platforms is PHP combined with
MySQL, and this is the environment that Moodle has been developed in (on Linux,
Windows, and Mac OS X). Moodle also uses the ADOdb library for database abstraction,
which means Moodle can use <a href="">more
than ten different brands of database</a> (unfortunately, though, it can not
yet <em><strong>set up tables</strong></em> in all these databases - more
on this later). <br><br>
<li><strong>Moodle should be easy to install, learn and modify</strong><br>
Early prototypes of Moodle (1999) were built using <a href="">Zope</a>
- an advanced object-oriented web application server. Unfortunately I found
that although the technology was pretty cool, it had a very steep learning
curve and was not very flexible in terms of system administration. The PHP
scripting language, on the other hand, is very easy to get into (especially
if you've done any programming using any other scripting language). Early
on I made the decision to avoid using a class-oriented design - again, to
keep it simple to understand for novices. Code reuse is instead achieved by
libraries of clearly-named functions and consistent layout of script files.
PHP is also easy to install (binaries are available for every platform) and
is widely available to the point that most web hosting services provide it
as standard.<br><br>
<li><strong>It should be easy to upgrade from one version to the next</strong><br>
Moodle knows what version it is (as well as the versions of all plug-in modules)
and a mechanism has been built-in so that Moodle can properly upgrade itself
to new versions (for example it can rename database tables or add new fields).
If using CVS in Unix for example, one can just do a &quot;cvs update -d&quot;
and then visit the site home page to complete an upgrade.<br><br>
<li><strong>It should be modular to allow for growth</strong><br>
Moodle has a number of features that are modular, including themes, activities,
interface languages, database schemas and course formats. This allows anyone
to add features to the main codebase or to even distribute them separately.
More on this below in the next section.<br><br>
<li><strong>It should be able to be used in conjunction with other systems</strong><br>
One thing Moodle does is keep all files for one course within a single, normal
directory on the server. This would allow a system administrator to provide
seamless forms of file-level access for each teacher, such as Appletalk, SMB,
NFS, FTP, WebDAV and so on. The authentication modules allow Moodle to use
LDAP, IMAP, POP3, NNTP and other databases as sources for user information.
Otherwise, there is work yet to do. Features planned
for Moodle in future versions include: import and export of Moodle data using XML-based
formats (including IMS and SCORM); and increased use of style sheets for
interface formatting (so that it can be integrated visually into other web sites).</li>
<h3><a name="contribute" id="contribute"></a>2. How you can contribute</h3>
<p>As mentioned above, Moodle has a number of features that are modular. Even
if you are not a programmer there are things you can change or help with.</p>
<p><strong><a name="activities" id="activities"></a>Learning Activities</strong></p>
<p>These are by far the most important modules, and reside in the 'mod' directory.
There are seven default modules: assignment, choice, forum, journal, quiz,
resource, and survey. Each module is in a separate subdirectory and consists
of the following mandatory elements (plus extra scripts unique to each module):</p>
<li>mod.html: a form to set up or update an instance of this module</li>
<li>version.php: defines some meta-info and provides upgrading code</li>
<li>icon.gif: a 16x16 icon for the module</li>
<li>db/: SQL dumps of all the required db tables and data (for each database
type) </li>
<li>index.php: a page to list all instances in a course</li>
<li>view.php: a page to view a particular instance</li>
<li>lib.php: any/all functions defined by the module should be in here. If
the modulename if called widget, then the required functions include:
<li>widget_add_instance() - code to add a new instance of widget</li>
<li>widget_update_instance() - code to update an existing instance</li>
<li>widget_delete_instance() - code to delete an instance</li>
<li>widget_user_outline() - given an instance, return a summary of a user's
<li>widget_user_complete() - given an instance, print details of a user's
<li>To avoid possible conflict, any module functions should be named starting
with widget_ and any constants you define should start with WIDGET_
<li>Lastly, each module will have some language files that contain strings
for that module. See below.</li>
<p>The easiest way to start a new learning activity module is to use the template
in <strong><a href="">mod/</a>.</strong>
Unzip it and follow the README inside. </p>
<p>You might also like to post first in the <a href="" target="_top">Activities
modules forum on Using Moodle</a>.</p>
<p> <strong><a name="themes" id="themes"></a>Themes</strong></p>
<p>Themes (or skins) define the look of a site. A number of simple themes are
provided in the main distribution, but you may want to copy one of these and
customise it to suit your own needs (eg local logo, colours, styles, graphics
etc). Each theme is in a subdirectory of the &quot;theme&quot; directory.
You can copy the &quot;standard&quot; theme or any other theme as a template
for your own.</p>
<p>Here is what each of the files does:</p>
<li><strong>config.php</strong>: defines your theme colours used throughout
the site</li>
<li><strong>styles.php</strong>: the style sheet, containing CSS definitions
for standard HTML elements as well as many Moodle elements.</li>
<li><strong>header.html</strong>: Included at the top of each page. This is
what you need to edit to add a logo at the top of pages, for example.</li>
<li><strong>footer.html</strong>: Included at the bottom of each page.</li>
<p>Note that Moodle upgrades <em>may</em> break themes slightly, so check the
release notes carefully if you are using a custom theme.</p>
<p>In particular, Moodle 2.0 will have a completely new display system, based
on a XSL transformations of XML output from Moodle. It is likely that the
themes for this will be a completely different format, but the advantage will
be a much higher possible degree of customisation (including moving elements
around the page).</p>
<p>More discussion about this in the <a href="">Themes
forum on Using Moodle</a>.<br>
<p><strong><a name="languages" id="languages"></a>Languages</strong></p>
<p>Moodle has been designed for internationalisation. Each 'string' or 'page'
of text that is displayed as part of the interface is drawn from a set of
language files. Each language is a subdirectory of the directory 'lang'. The
structure of the lang directory is as follows:</p>
<p><strong>lang/en</strong> - directory containing all files for one language
(eg English)</p>
<li>moodle.php - strings for main interface</li>
<li>assignment.php - strings for assignment module</li>
<li>choice.php - strings for choice module</li>
<li>forum.php - strings for forum module</li>
<li>journal.php - strings for journal module </li>
<li>quiz.php - strings for quiz module</li>
<li>resource.php - strings for resource module</li>
<li>survey.php - strings for survey module</li>
<li>.... plus other modules if any.<br>
A string is called from these files using the <strong><em>get_string()</em></strong><em>
</em>or<em> <strong>print_string()</strong> </em>functions. Each string
supports variable substitution, to support variable ordering in different
</em>eg $strdueby = get_string(&quot;assignmentdueby&quot;, &quot;assignment&quot;,
userdate($date)); <br>
If a string doesn't exist in a particular language, then the equivalent
in English will automatically be used instead.</li>
<p><strong>lang/en/help</strong> - contains whole help pages (for popup context-sensitive
<p>Main help pages are situated here, while help pages specific to each module
are located in subdirectories with the module's name.</p>
<p>You can insert a helpbutton in a page with the helpbutton function.</p>
<p>eg helpbutton(&quot;text&quot;, &quot;Click here for help about text&quot;);</p>
<p>and for modules:</p>
<p>helpbutton(&quot;forumtypes&quot;, &quot;Forum types&quot;, &quot;forum&quot;);</p>
<p>Note that you can edit languages online, using the administration web tools
under &quot;Check this language&quot;. This makes it easy to not to only create
new languages but to refine existing ones. If you are starting a new language,
please contact me, <a href="">Martin Dougiamas</a>. </p>
<p>You might also like to post in the <a href="" target="_top">Languages
forum on Using Moodle</a>. </p>
<p>If you are maintaining a language an ongoing basis, I can give you <a href="cvs.html">CVS
write access to the Moodle source code</a> so that you can directly maintain
the files.</p>
<strong><a name="database" id="database"></a>Database Schemas</strong></p>
<p>Given a working database with defined tables, the intentionally simple SQL
used in Moodle should work fine with a wide variety of database brands.</p>
<p>A problem exists with <strong>automatically creating</strong> new tables
in a database, which is what Moodle tries to do upon initial installation.
Because every database is very different, there doesn't yet exist any way
to do this in a platform-independent way. To support this automation in each
database, schemas can be created that list the required SQL to create Moodle
tables in a particular database. These are files in <strong>lib/db</strong>
and inside the <strong>db</strong> subdirectory of each module.</p>
<p>Currently, only MySQL is supported because that's what I know. If you are
familiar with another database (especially open source databases) and are
willing to help port the MySQL schema, please get in contact with me (<a href="">Martin
<p><strong><a name="courseformats" id="courseformats"></a>Course Formats</strong></p>
<p>Moodle 1.x supports three different course formats: weekly, topics and social.
<p>These are a little more connected to the rest of the code (and hence, less
&quot;pluggable&quot;) but it is still quite easy to add new ones.</p>
<p>If you have any ideas for different formats that you need or would like to
see, get in touch with me and I'll do my absolute best to have them available
in future releases.</p>
<p><strong><a name="doc" id="doc"></a>Documentation and articles</strong></p>
<p>If you feel like writing a tutorial, an article, an academic paper or anything
else about Moodle, please do! </p>
<p>Put it on the web and make sure you include links to <a href=""></a></p>
<p><strong><a name="bugs" id="bugs"></a>Participating in the bug tracker</strong></p>
<p>Finally, I would like to invite you to register on the &quot;bug tracker&quot;
at <a href=""></a> so you can file any
bugs that you find and perhaps participate in discussing and fixing them.
<p>&quot;Bugs&quot; not only includes software bugs with current versions of
Moodle, but also new ideas, feature requests and even constructive criticism
of existing features. The beauty of open source is that anyone can participate
in some way and help to create a better product for all of us to enjoy. In
this project, your input is very welcome!</p>
<p align="center">Thanks for using Moodle!</p>
<p align="center">Cheers,<br>
<a href="" target="_top">Martin Dougiamas</a></p>
<p align="CENTER"><font size="1"><a href="." target="_top">Moodle Documentation</a></font></p>
<p align="CENTER"><font size="1">Version: $Id: developer.html,v 1.2 2001/12/09
10:34:19 martin Exp $</font></p>
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