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<TITLE>Moodle Docs: Developers Manual</TITLE>
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<BODY BGCOLOR="#FFFFFF">
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<H2>Developers Manual</H2>
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<P>This document describes some of Moodle's design and how you can contribute.</P>
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<P>Sections in this document:</P>
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<OL>
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<LI><A HREF="#architecture">Moodle architecture</A></LI>
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<LI><A HREF="#contribute">How you can contribute</A>
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<ul>
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<li><A HREF="#activities">Learning activities</A></li>
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<li><A HREF="#themes">Themes</A></li>
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<li><A HREF="#languages">Languages</A></li>
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<li><A HREF="#database">Database Schemas</A></li>
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<li><a href="#courseformats">Course formats</a></li>
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<li><a href="#doc">Documentation and articles</a></li>
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<li><a href="#bugs">Participating in the bug tracker</a></li>
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</ul>
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</LI>
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</OL>
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<P> </P>
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<H3><a name="architecture"></a>1. Moodle architecture</H3>
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<P>From a system administrator's perspective, Moodle has been designed according
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to the following criteria:</P>
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<ol>
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<li><strong>Moodle should run on the widest variety of platforms</strong><br>
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<br>
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The web application platform that runs on most platforms is PHP combined with
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MySQL, and this is the environment that Moodle has been developed in (on Linux,
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Windows, and Mac OS X). Moodle also uses the ADOdb library for database abstraction,
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which means Moodle can use <a href="http://php.weblogs.com/ADOdb_manual#drivers">more
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than ten different brands of database</a> (unfortunately, though, it can not
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yet <em><strong>set up tables</strong></em> in all these databases - more
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on this later). <br><br>
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</li>
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<li><strong>Moodle should be easy to install, learn and modify</strong><br>
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<br>
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Early prototypes of Moodle (1999) were built using <a href="http://www.zope.org/">Zope</a>
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- an advanced object-oriented web application server. Unfortunately I found
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that although the technology was pretty cool, it had a very steep learning
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curve and was not very flexible in terms of system administration. The PHP
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scripting language, on the other hand, is very easy to get into (especially
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if you've done any programming using any other scripting language). Early
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on I made the decision to avoid using a class-oriented design - again, to
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keep it simple to understand for novices. Code reuse is instead achieved by
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libraries of clearly-named functions and consistent layout of script files.
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PHP is also easy to install (binaries are available for every platform) and
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is widely available to the point that most web hosting services provide it
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as standard.<br><br>
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</li>
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<li><strong>It should be easy to upgrade from one version to the next</strong><br>
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<br>
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Moodle knows what version it is (as well as the versions of all plug-in modules)
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and a mechanism has been built-in so that Moodle can properly upgrade itself
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to new versions (for example it can rename database tables or add new fields).
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If using CVS in Unix for example, one can just do a "cvs update -d"
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and then visit the site home page to complete an upgrade.<br><br>
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</li>
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<li><strong>It should be modular to allow for growth</strong><br>
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<br>
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Moodle has a number of features that are modular, including themes, activities,
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interface languages, database schemas and course formats. This allows anyone
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to add features to the main codebase or to even distribute them separately.
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More on this below in the next section.<br><br>
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</li>
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<li><strong>It should be able to be used in conjunction with other systems</strong><br>
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<br>
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One thing Moodle does is keep all files for one course within a single, normal
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directory on the server. This would allow a system administrator to provide
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seamless forms of file-level access for each teacher, such as Appletalk, SMB,
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NFS, FTP, WebDAV and so on. The authentication modules allow Moodle to use
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LDAP, IMAP, POP3, NNTP and other databases as sources for user information.
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Otherwise, there is work yet to do. Features planned
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for Moodle in future versions include: import and export of Moodle data using XML-based
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formats (including IMS and SCORM); and increased use of style sheets for
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interface formatting (so that it can be integrated visually into other web sites).</li>
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</ol>
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<p> </p>
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<H3><a name="contribute" id="contribute"></a>2. How you can contribute</H3>
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<P>As mentioned above, Moodle has a number of features that are modular. Even
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if you are not a programmer there are things you can change or help with.</P>
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<P><strong><a name="activities" id="activities"></a>Learning Activities</strong></P>
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<blockquote>
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<p>These are by far the most important modules, and reside in the 'mod' directory.
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There are seven default modules: assignment, choice, forum, journal, quiz, resource,
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and survey. Each module is in a separate subdirectory and consists of the
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following mandatory elements (plus extra scripts unique to each module):</p>
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<ul>
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<li>mod.html: a form to set up or update an instance of this module</li>
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<li>version.php: defines some meta-info and provides upgrading code</li>
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<li>icon.gif: a 16x16 icon for the module</li>
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<li>db/: SQL dumps of all the required db tables and data (for each database
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type) </li>
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<li>index.php: a page to list all instances in a course</li>
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<li>view.php: a page to view a particular instance</li>
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<li>lib.php: any/all functions defined by the module should be in here. If
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the modulename if called widget, then the required functions include:
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<ul>
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<li>widget_add_instance() - code to add a new instance of widget</li>
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<li>widget_update_instance() - code to update an existing instance</li>
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<li>widget_delete_instance() - code to delete an instance</li>
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<li>widget_user_outline() - given an instance, return a summary of a user's
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contribution</li>
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<li>widget_user_complete() - given an instance, print details of a user's
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contribution<br>
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</li>
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<li>To avoid possible conflict, any module functions should be named starting
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with widget_ and any constants you define should start with WIDGET_
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</li>
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</ul>
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</li>
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<li>Lastly, each module will have some language files that contain strings
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for that module. See below.<br>
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</li>
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</ul>
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</blockquote>
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<p> <strong><a name="themes" id="themes"></a>Themes</strong></p>
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<blockquote>
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<p>Themes (or skins) define the look of a site. A number of simple themes are
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provided in the main distribution, but you may want to copy one of these and
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customise it to suit your own needs (eg local logo, colours, styles, graphics
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etc)</p>
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<p>Each theme is in a subdirectory of the "theme" directory. You can
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copy the "standard" theme as a template.<br>
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</p>
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</blockquote>
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<p><strong><a name="languages" id="languages"></a>Languages</strong></p>
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<blockquote>
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<p>Moodle has been designed for internationalisation. Each 'string' or 'page'
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of text that is displayed as part of the interface is drawn from a set of
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language files. Each language is a subdirectory of the directory 'lang'. The
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structure of the lang directory is as follows:</p>
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<p><strong>lang/en</strong> - directory containing all files for one language
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(eg English)</p>
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<ul>
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<li>moodle.php - strings for main interface</li>
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<li>assignment.php - strings for assignment module</li>
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<li>choice.php - strings for choice module</li>
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<li>forum.php - strings for forum module</li>
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<li>journal.php - strings for journal module </li>
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<li>quiz.php - strings for quiz module</li>
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<li>resource.php - strings for resource module</li>
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<li>survey.php - strings for survey module</li>
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<li>.... plus other modules if any.<br>
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<br>
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A string is called from these files using the <strong><em>get_string()</em></strong><em>
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</em>or<em> <strong>print_string()</strong> </em>functions. Each string
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supports variable substitution, to support variable ordering in different
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languages.<em><br>
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<br>
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</em>eg $strdueby = get_string("assignmentdueby", "assignment",
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userdate($date)); <br>
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<br>
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If a string doesn't exist in a particular language, then the equivalent
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in English will automatically be used instead.</li>
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</ul>
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<p><strong>lang/en/help</strong> - contains whole help pages (for popup context-sensitive
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help)</p>
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<blockquote>
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<p>Main help pages are situated here, while help pages specific to each module
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are located in subdirectories with the module's name.</p>
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<p>You can insert a helpbutton in a page with the helpbutton function.</p>
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<p>eg helpbutton("text", "Click here for help about text");</p>
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<p>and for modules:</p>
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<p>helpbutton("forumtypes", "Forum types", "forum");</p>
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</blockquote>
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</blockquote>
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<p><br>
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<strong><a name="database" id="database"></a>Database Schemas</strong></p>
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<blockquote>
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<p>Given a working database with defined tables, the intentionally simple SQL
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used in Moodle should work fine with a wide variety of database brands.</p>
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<p>A problem exists with <strong>automatically creating</strong> new tables
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in a database, which is what Moodle tries to do upon initial installation.
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Because every database is very different, there doesn't yet exist any way
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to do this in a platform-independent way. To support this automation in each
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database, schemas can be created that list the required SQL to create Moodle
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tables in a particular database. These are files in <strong>lib/db</strong>
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and inside the <strong>db</strong> subdirectory of each module.</p>
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<p>Currently, only MySQL is supported because that's what I know. If you are
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familiar with another database (especially open source databases) and are
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willing to help port the MySQL schema, please get in contact with me (<a href="mailto:martin@moodle.com">martin@moodle.com</a>).</p>
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</blockquote>
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<p> </p>
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<p><strong><a name="courseformats" id="courseformats"></a>Course Formats</strong></p>
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<blockquote>
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<p>Moodle 1.0 supports three different course formats: weekly, topics and social.
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</p>
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<p>These are a little more connected to the rest of the code (and hence, less
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"pluggable") but it is still quite easy to add new ones.</p>
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<p>If you have any ideas for different formats that you need or would like to
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see, get in touch with me and I'll do my absolute best to have them available
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in future releases.</p>
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</blockquote>
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<p> </p>
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<p><strong><a name="doc" id="doc"></a>Documentation and articles</strong></p>
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<blockquote>
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<p>If you feel like writing a tutorial, an article, an academic paper or anything
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else about Moodle, please do! Put it on the web and make sure you include
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links to <a href="http://moodle.com/">http://moodle.com/</a></p>
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</blockquote>
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<p> </p>
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<p><strong><a name="bugs" id="bugs"></a>Participating in the bug tracker</strong></p>
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<blockquote>
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<p>Finally, I would like to invite you to register on the "bug tracker"
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at <a href="http://bugs.moodle.org">bugs.moodle.org</a> so you can file any
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bugs that you find and perhaps participate in discussing and fixing them.
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</p>
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<p>"Bugs" not only includes software bugs with current versions of
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Moodle, but also new ideas, feature requests and even constructive criticism
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of existing features. The beauty of open source is that anyone can participate
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in some way and help to create a better product for all of us to enjoy. In
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this project, your input is very welcome!</p>
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</blockquote>
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<p> </p>
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<blockquote>
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<blockquote>
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<blockquote>
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<p align="center">Thanks for using Moodle!</p>
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<p align="center">Cheers,<br>
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<a href="http://dougiamas.com/" target="_top">Martin Dougiamas</a></p>
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</blockquote>
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</blockquote>
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</blockquote>
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<p> </p>
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<p> </p>
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<blockquote>
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<p> </p>
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</blockquote>
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<P ALIGN="CENTER"><FONT SIZE="1"><A HREF="." TARGET="_top">Moodle Documentation</A></FONT></P>
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<P ALIGN="CENTER"><FONT SIZE="1">Version: $Id: developer.html,v 1.2 2001/12/09
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10:34:19 martin Exp $</FONT></P>
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</BODY>
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