diff --git a/lib/db/install.xml b/lib/db/install.xml
index 277e4011547..0340da70c57 100644
--- a/lib/db/install.xml
+++ b/lib/db/install.xml
@@ -128,7 +128,7 @@
         <INDEX NAME="child_course" UNIQUE="false" FIELDS="child_course" PREVIOUS="parent_course"/>
       </INDEXES>
     </TABLE>
-    <TABLE NAME="course_modules" COMMENT="course_modules table retrofitted from MySQL" PREVIOUS="course_meta" NEXT="course_modules_completion">
+    <TABLE NAME="course_modules" COMMENT="course_modules table retrofitted from MySQL" PREVIOUS="course_meta" NEXT="course_modules_availability">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="course"/>
         <FIELD NAME="course" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="module"/>
@@ -137,6 +137,7 @@
         <FIELD NAME="section" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="instance" NEXT="idnumber"/>
         <FIELD NAME="idnumber" TYPE="char" LENGTH="100" NOTNULL="false" SEQUENCE="false" ENUM="false" COMMENT="customizable idnumber" PREVIOUS="section" NEXT="added"/>
         <FIELD NAME="added" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="idnumber" NEXT="score"/>
+
         <FIELD NAME="score" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="added" NEXT="indent"/>
         <FIELD NAME="indent" TYPE="int" LENGTH="5" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="score" NEXT="visible"/>
         <FIELD NAME="visible" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="false" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="indent" NEXT="visibleold"/>
@@ -146,12 +147,17 @@
         <FIELD NAME="groupmembersonly" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="only members of any group are allowed to access the activity" PREVIOUS="groupingid" NEXT="completion"/>
         <FIELD NAME="completion" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Whether the completion-tracking facilities are enabled for this activity. 0 = not enabled (database default) 1 = manual tracking, user can tick this activity off (UI default for most activity types) 2 = automatic tracking, system should mark completion according to rules specified in course_moduleS_completion" PREVIOUS="groupmembersonly" NEXT="completiongradeitemnumber"/>
         <FIELD NAME="completiongradeitemnumber" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="Grade-item number used to track automatic completion, if applicable." PREVIOUS="completion" NEXT="completionview"/>
+
         <FIELD NAME="completionview" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Controls whether a page view is part of the automatic completion requirements for this activity. 0 = view not required 1 = view required" PREVIOUS="completiongradeitemnumber" NEXT="completionexpected"/>
-        <FIELD NAME="completionexpected" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Date at which students are expected to complete this activity. This field is used when displaying student progress." PREVIOUS="completionview"/>
+        <FIELD NAME="completionexpected" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Date at which students are expected to complete this activity. This field is used when displaying student progress." PREVIOUS="completionview" NEXT="availablefrom"/>
+        <FIELD NAME="availablefrom" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="If set non-zero, the activity only becomes available from the time given here." PREVIOUS="completionexpected" NEXT="availableuntil"/>
+        <FIELD NAME="availableuntil" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="If set non-zero, the activity is only available until the time given here." PREVIOUS="availablefrom" NEXT="showavailability"/>
+        <FIELD NAME="showavailability" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="If this field is set to 1 and the activity is not available because the 'availablefrom' date has not been reached, or one of the conditions in course_modules_availability is not matched, then the item will be displayed greyed-out (unclickable) with an information message such as 'Available from (date)'. Otherwise, the item will not be displayed to students at all." PREVIOUS="availableuntil"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="groupingid"/>
         <KEY NAME="groupingid" TYPE="foreign" FIELDS="groupingid" REFTABLE="groupings" REFFIELDS="id" PREVIOUS="primary"/>
+
       </KEYS>
       <INDEXES>
         <INDEX NAME="visible" UNIQUE="false" FIELDS="visible" NEXT="course"/>
@@ -161,7 +167,27 @@
         <INDEX NAME="idnumber-course" UNIQUE="false" FIELDS="idnumber, course" COMMENT="non unique index (although programatically we are guarantying some sort of uniqueness both under this table and the grade_items one). TODO: We need a central store of module idnumbers in the future." PREVIOUS="instance"/>
       </INDEXES>
     </TABLE>
-    <TABLE NAME="course_modules_completion" COMMENT="Stores the completion state (completed or not completed, etc) of each user on each activity." PREVIOUS="course_modules" NEXT="course_sections">
+
+    <TABLE NAME="course_modules_availability" COMMENT="Table stores conditions that affect whether a module/activity is currently available to students or not." PREVIOUS="course_modules" NEXT="course_modules_completion">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="coursemoduleid"/>
+        <FIELD NAME="coursemoduleid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="ID of the module whose availability is being restricted by this condition." PREVIOUS="id" NEXT="sourcecmid"/>
+        <FIELD NAME="sourcecmid" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="If this condition is based on completion of another activity, then this is the course-module ID of that activity. Otherwise null." PREVIOUS="coursemoduleid" NEXT="requiredcompletion"/>
+        <FIELD NAME="requiredcompletion" TYPE="int" LENGTH="1" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="If this condition is on a module's completion, then this should be set to the required completion state. Otherwise null. Suitable values are 1 = completed, 2 = completed-passed, 3 = completed-failed." PREVIOUS="sourcecmid" NEXT="gradeitemid"/>
+        <FIELD NAME="gradeitemid" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="If this condition is based on a gradebook score, the item ID is given here (and the item will now not be available until a value is achieved for that grade). Otherwise null." PREVIOUS="requiredcompletion" NEXT="grademin"/>
+        <FIELD NAME="grademin" TYPE="number" LENGTH="10" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="If set, this is the minimum grade that must be reached in order for this module to appear. Otherwise null." PREVIOUS="gradeitemid" NEXT="grademax"/>
+        <FIELD NAME="grademax" TYPE="number" LENGTH="10" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="If set, this is the maximum grade that can be reached in order to display this item. Otherwise null." PREVIOUS="grademin"/>
+
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="fk_coursemoduleid"/>
+        <KEY NAME="fk_coursemoduleid" TYPE="foreign" FIELDS="coursemoduleid" REFTABLE="course_modules" REFFIELDS="id" PREVIOUS="primary" NEXT="fk_sourcecmid"/>
+        <KEY NAME="fk_sourcecmid" TYPE="foreign" FIELDS="sourcecmid" REFTABLE="course_modules" REFFIELDS="id" PREVIOUS="fk_coursemoduleid" NEXT="fk_gradeitemid"/>
+        <KEY NAME="fk_gradeitemid" TYPE="foreign" FIELDS="gradeitemid" REFTABLE="grade_items" REFFIELDS="id" PREVIOUS="fk_sourcecmid"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="course_modules_completion" COMMENT="Stores the completion state (completed or not completed, etc) of each user on each activity." PREVIOUS="course_modules_availability" NEXT="course_sections">
+
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="coursemoduleid"/>
         <FIELD NAME="coursemoduleid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="Activity that has been completed (or not)." PREVIOUS="id" NEXT="userid"/>
@@ -171,6 +197,7 @@
         <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="Time at which the completion state last changed." PREVIOUS="viewed"/>
       </FIELDS>
       <KEYS>
+
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
       </KEYS>
       <INDEXES>
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index 8904ad4c533..39a7f661be3 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -1056,6 +1056,61 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint($result, 2008111801);
     }
 
+    if ($result && $oldversion < 2008112400) {
+
+    /// Define field availablefrom to be added to course_modules
+        $table = new xmldb_table('course_modules');
+        $field = new xmldb_field('availablefrom', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, null, null, '0', 'completionexpected');
+
+    /// Conditionally launch add field availablefrom
+        if (!$dbman->field_exists($table, $field)) {
+            $dbman->add_field($table, $field);
+        }
+
+    /// Define field availableuntil to be added to course_modules
+        $field = new xmldb_field('availableuntil', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, null, null, '0', 'availablefrom');
+
+    /// Conditionally launch add field availableuntil
+        if (!$dbman->field_exists($table, $field)) {
+            $dbman->add_field($table, $field);
+        }
+        
+    /// Define field showavailability to be added to course_modules
+        $field = new xmldb_field('showavailability', XMLDB_TYPE_INTEGER, '1', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, null, null, '0', 'availableuntil');
+
+    /// Conditionally launch add field showavailability
+        if (!$dbman->field_exists($table, $field)) {
+            $dbman->add_field($table, $field);
+        }
+        
+    /// Define table course_modules_availability to be created
+        $table = new xmldb_table('course_modules_availability');
+
+    /// Adding fields to table course_modules_availability
+        $table->add_field('id', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, XMLDB_NOTNULL, XMLDB_SEQUENCE, null, null, null);
+        $table->add_field('coursemoduleid', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, null, null, null);
+        $table->add_field('sourcecmid', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, null, null, null, null, null);
+        $table->add_field('requiredcompletion', XMLDB_TYPE_INTEGER, '1', XMLDB_UNSIGNED, null, null, null, null, null);
+        $table->add_field('gradeitemid', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, null, null, null, null, null);
+        $table->add_field('grademin', XMLDB_TYPE_NUMBER, '10, 5', null, null, null, null, null, null);
+        $table->add_field('grademax', XMLDB_TYPE_NUMBER, '10, 5', null, null, null, null, null, null);
+
+    /// Adding keys to table course_modules_availability
+        $table->add_key('primary', XMLDB_KEY_PRIMARY, array('id'));
+        $table->add_key('fk_coursemoduleid', XMLDB_KEY_FOREIGN, array('coursemoduleid'), 'course_modules', array('id'));
+        $table->add_key('fk_sourcecmid', XMLDB_KEY_FOREIGN, array('sourcecmid'), 'course_modules', array('id'));
+        $table->add_key('fk_gradeitemid', XMLDB_KEY_FOREIGN, array('gradeitemid'), 'grade_items', array('id'));
+
+    /// Conditionally launch create table for course_modules_availability
+        if (!$dbman->table_exists($table)) {
+            $dbman->create_table($table);
+        }
+
+    /// Main savepoint reached
+        upgrade_main_savepoint($result, 2008112400);
+    }
+    
+    
     return $result;
 }
 
diff --git a/version.php b/version.php
index b7338a196f2..862ceefb0ef 100644
--- a/version.php
+++ b/version.php
@@ -6,7 +6,7 @@
 // This is compared against the values stored in the database to determine
 // whether upgrades should be performed (see lib/db/*.php)
 
-    $version = 2008112101;  // YYYYMMDD   = date of the last version bump
+    $version = 2008112400;  // YYYYMMDD   = date of the last version bump
                             //         XX = daily increments
 
     $release = '2.0 dev (Build: 20081124)';  // Human-friendly version name