From 4f089b2155fd7487beb99d20608975315016a5d1 Mon Sep 17 00:00:00 2001
From: tjhunt <tjhunt>
Date: Fri, 15 Aug 2008 07:23:18 +0000
Subject: [PATCH] MDL-6095 - Question bank tables are created by the quiz
 module. The really core tables are now created by lib/db, the
 datasetdependent tables are not created by the datasetdependent question
 type, and the question_numerical_units table is now created by the numerical
 question type. The last two are shared by the calculated question type, but
 there is no problem with them being created in the order they are now created
 in. In the past, before the policy that upgrade to 2.0 woudl have to go via
 1.9, there would have been bit problems to do with the order of updates, but
 fortunately that is no longer an issue.

---
 lib/db/install.xml                            | 115 +++++++++++-
 mod/quiz/db/install.xml                       | 171 +-----------------
 question/type/calculated/db/install.xml       |   2 +-
 question/type/datasetdependent/db/install.xml |  48 +++++
 question/type/datasetdependent/db/upgrade.php |  38 ++++
 question/type/numerical/db/install.xml        |  17 +-
 6 files changed, 217 insertions(+), 174 deletions(-)
 create mode 100644 question/type/datasetdependent/db/install.xml
 create mode 100644 question/type/datasetdependent/db/upgrade.php

diff --git a/lib/db/install.xml b/lib/db/install.xml
index f3ea7b4830..61bf12a08d 100644
--- a/lib/db/install.xml
+++ b/lib/db/install.xml
@@ -934,7 +934,7 @@
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
       </KEYS>
     </TABLE>
-    <TABLE NAME="user_info_data" COMMENT="Data for the customisable user fields" PREVIOUS="user_info_category" NEXT="mnet_enrol_course">
+    <TABLE NAME="user_info_data" COMMENT="Data for the customisable user fields" PREVIOUS="user_info_category" NEXT="question_categories">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="userid"/>
         <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="id from the user table" PREVIOUS="id" NEXT="fieldid"/>
@@ -945,7 +945,118 @@
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
       </KEYS>
     </TABLE>
-    <TABLE NAME="mnet_enrol_course" COMMENT="Information about courses on remote hosts" PREVIOUS="user_info_data" NEXT="mnet_enrol_assignments">
+    <TABLE NAME="question_categories" COMMENT="Categories are for grouping questions" PREVIOUS="user_info_data" NEXT="question">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="name"/>
+        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="contextid"/>
+        <FIELD NAME="contextid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="context that this category is shared in" PREVIOUS="name" NEXT="info"/>
+        <FIELD NAME="info" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="contextid" NEXT="stamp"/>
+        <FIELD NAME="stamp" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="info" NEXT="parent"/>
+        <FIELD NAME="parent" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="stamp" NEXT="sortorder"/>
+        <FIELD NAME="sortorder" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="999" SEQUENCE="false" ENUM="false" PREVIOUS="parent"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="parent"/>
+        <KEY NAME="parent" TYPE="foreign" FIELDS="parent" REFTABLE="question_categories" REFFIELDS="id" COMMENT="note that to make this recursive FK working someday, the parent field must be declared NULL" PREVIOUS="primary"/>
+      </KEYS>
+      <INDEXES>
+        <INDEX NAME="contextid" UNIQUE="false" FIELDS="contextid" COMMENT="links to context table"/>
+      </INDEXES>
+    </TABLE>
+    <TABLE NAME="question" COMMENT="The questions themselves" PREVIOUS="question_categories" NEXT="question_answers">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="category"/>
+        <FIELD NAME="category" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="parent"/>
+        <FIELD NAME="parent" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="category" NEXT="name"/>
+        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="parent" NEXT="questiontext"/>
+        <FIELD NAME="questiontext" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="name" NEXT="questiontextformat"/>
+        <FIELD NAME="questiontextformat" TYPE="int" LENGTH="2" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="questiontext" NEXT="image"/>
+        <FIELD NAME="image" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="questiontextformat" NEXT="generalfeedback"/>
+        <FIELD NAME="generalfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="to store the question feedback" PREVIOUS="image" NEXT="defaultgrade"/>
+        <FIELD NAME="defaultgrade" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="generalfeedback" NEXT="penalty"/>
+        <FIELD NAME="penalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0.1" SEQUENCE="false" ENUM="false" PREVIOUS="defaultgrade" NEXT="qtype"/>
+        <FIELD NAME="qtype" TYPE="char" LENGTH="20" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="penalty" NEXT="length"/>
+        <FIELD NAME="length" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="qtype" NEXT="stamp"/>
+        <FIELD NAME="stamp" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="length" NEXT="version"/>
+        <FIELD NAME="version" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="stamp" NEXT="hidden"/>
+        <FIELD NAME="hidden" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="version" NEXT="timecreated"/>
+        <FIELD NAME="timecreated" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="time question was created" PREVIOUS="hidden" NEXT="timemodified"/>
+        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="time that question was last modified" PREVIOUS="timecreated" NEXT="createdby"/>
+        <FIELD NAME="createdby" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="userid of person who created this question" PREVIOUS="timemodified" NEXT="modifiedby"/>
+        <FIELD NAME="modifiedby" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="userid of person who last edited this question" PREVIOUS="createdby"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="category"/>
+        <KEY NAME="category" TYPE="foreign" FIELDS="category" REFTABLE="question_categories" REFFIELDS="id" PREVIOUS="primary" NEXT="parent"/>
+        <KEY NAME="parent" TYPE="foreign" FIELDS="parent" REFTABLE="question" REFFIELDS="id" COMMENT="note that to make this recursive FK working someday, the parent field must be declared NULL" PREVIOUS="category" NEXT="createdby"/>
+        <KEY NAME="createdby" TYPE="foreign" FIELDS="createdby" REFTABLE="user" REFFIELDS="id" COMMENT="foreign (createdby) references user (id)" PREVIOUS="parent" NEXT="modifiedby"/>
+        <KEY NAME="modifiedby" TYPE="foreign" FIELDS="modifiedby" REFTABLE="user" REFFIELDS="id" COMMENT="foreign (modifiedby) references user (id)" PREVIOUS="createdby"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="question_answers" COMMENT="Answers, with a fractional grade (0-1) and feedback" PREVIOUS="question" NEXT="question_attempts">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="answer"/>
+        <FIELD NAME="answer" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="fraction"/>
+        <FIELD NAME="fraction" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answer" NEXT="feedback"/>
+        <FIELD NAME="feedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="fraction"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
+        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="question_attempts" COMMENT="Student attempts. This table gets extended by the modules" PREVIOUS="question_answers" NEXT="question_states">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="modulename"/>
+        <FIELD NAME="modulename" TYPE="char" LENGTH="20" NOTNULL="true" DEFAULT="quiz" SEQUENCE="false" ENUM="false" PREVIOUS="id"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="question_states" COMMENT="Stores user responses to an attempt, and percentage grades" PREVIOUS="question_attempts" NEXT="question_sessions">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="attempt"/>
+        <FIELD NAME="attempt" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="attempt" NEXT="originalquestion"/>
+        <FIELD NAME="originalquestion" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="seq_number"/>
+        <FIELD NAME="seq_number" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="originalquestion" NEXT="answer"/>
+        <FIELD NAME="answer" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="seq_number" NEXT="timestamp"/>
+        <FIELD NAME="timestamp" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answer" NEXT="event"/>
+        <FIELD NAME="event" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timestamp" NEXT="grade"/>
+        <FIELD NAME="grade" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="event" NEXT="raw_grade"/>
+        <FIELD NAME="raw_grade" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="grade" NEXT="penalty"/>
+        <FIELD NAME="penalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="raw_grade"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="attempt"/>
+        <KEY NAME="attempt" TYPE="foreign" FIELDS="attempt" REFTABLE="question_attempts" REFFIELDS="id" PREVIOUS="primary" NEXT="question"/>
+        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="attempt"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="question_sessions" COMMENT="Gives ids of the newest open and newest graded states" PREVIOUS="question_states" NEXT="mnet_enrol_course">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="attemptid"/>
+        <FIELD NAME="attemptid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="questionid"/>
+        <FIELD NAME="questionid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="attemptid" NEXT="newest"/>
+        <FIELD NAME="newest" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="questionid" NEXT="newgraded"/>
+        <FIELD NAME="newgraded" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="newest" NEXT="sumpenalty"/>
+        <FIELD NAME="sumpenalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="newgraded" NEXT="manualcomment"/>
+        <FIELD NAME="manualcomment" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="sumpenalty"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="attemptid"/>
+        <KEY NAME="attemptid" TYPE="foreign" FIELDS="attemptid" REFTABLE="question_attempts" REFFIELDS="id" PREVIOUS="primary" NEXT="questionid"/>
+        <KEY NAME="questionid" TYPE="foreign" FIELDS="questionid" REFTABLE="question" REFFIELDS="id" PREVIOUS="attemptid" NEXT="newest"/>
+        <KEY NAME="newest" TYPE="foreign" FIELDS="newest" REFTABLE="question_states" REFFIELDS="id" PREVIOUS="questionid" NEXT="newgraded"/>
+        <KEY NAME="newgraded" TYPE="foreign" FIELDS="newgraded" REFTABLE="question_states" REFFIELDS="id" PREVIOUS="newest"/>
+      </KEYS>
+      <INDEXES>
+        <INDEX NAME="attemptid-questionid" UNIQUE="true" FIELDS="attemptid, questionid"/>
+      </INDEXES>
+    </TABLE>
+    <TABLE NAME="mnet_enrol_course" COMMENT="Information about courses on remote hosts" PREVIOUS="question_sessions" NEXT="mnet_enrol_assignments">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" COMMENT="Unique remote-course ID" NEXT="hostid"/>
         <FIELD NAME="hostid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="remoteid"/>
diff --git a/mod/quiz/db/install.xml b/mod/quiz/db/install.xml
index b40eab101b..e9e6ad60ad 100755
--- a/mod/quiz/db/install.xml
+++ b/mod/quiz/db/install.xml
@@ -4,176 +4,7 @@
     xsi:noNamespaceSchemaLocation="../../../lib/xmldb/xmldb.xsd"
 >
   <TABLES>
-    <TABLE NAME="question_categories" COMMENT="Categories are for grouping questions" NEXT="question">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="name"/>
-        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="contextid"/>
-        <FIELD NAME="contextid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="context that this category is shared in" PREVIOUS="name" NEXT="info"/>
-        <FIELD NAME="info" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="contextid" NEXT="stamp"/>
-        <FIELD NAME="stamp" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="info" NEXT="parent"/>
-        <FIELD NAME="parent" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="stamp" NEXT="sortorder"/>
-        <FIELD NAME="sortorder" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="999" SEQUENCE="false" ENUM="false" PREVIOUS="parent"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="parent"/>
-        <KEY NAME="parent" TYPE="foreign" FIELDS="parent" REFTABLE="question_categories" REFFIELDS="id" COMMENT="note that to make this recursive FK working someday, the parent field must be declared NULL" PREVIOUS="primary"/>
-      </KEYS>
-      <INDEXES>
-        <INDEX NAME="contextid" UNIQUE="false" FIELDS="contextid" COMMENT="links to context table"/>
-      </INDEXES>
-    </TABLE>
-    <TABLE NAME="question" COMMENT="The questions themselves" PREVIOUS="question_categories" NEXT="question_answers">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="category"/>
-        <FIELD NAME="category" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="parent"/>
-        <FIELD NAME="parent" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="category" NEXT="name"/>
-        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="parent" NEXT="questiontext"/>
-        <FIELD NAME="questiontext" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="name" NEXT="questiontextformat"/>
-        <FIELD NAME="questiontextformat" TYPE="int" LENGTH="2" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="questiontext" NEXT="image"/>
-        <FIELD NAME="image" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="questiontextformat" NEXT="generalfeedback"/>
-        <FIELD NAME="generalfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="to store the question feedback" PREVIOUS="image" NEXT="defaultgrade"/>
-        <FIELD NAME="defaultgrade" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="generalfeedback" NEXT="penalty"/>
-        <FIELD NAME="penalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0.1" SEQUENCE="false" ENUM="false" PREVIOUS="defaultgrade" NEXT="qtype"/>
-        <FIELD NAME="qtype" TYPE="char" LENGTH="20" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="penalty" NEXT="length"/>
-        <FIELD NAME="length" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="qtype" NEXT="stamp"/>
-        <FIELD NAME="stamp" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="length" NEXT="version"/>
-        <FIELD NAME="version" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="stamp" NEXT="hidden"/>
-        <FIELD NAME="hidden" TYPE="int" LENGTH="1" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="version" NEXT="timecreated"/>
-        <FIELD NAME="timecreated" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="time question was created" PREVIOUS="hidden" NEXT="timemodified"/>
-        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="time that question was last modified" PREVIOUS="timecreated" NEXT="createdby"/>
-        <FIELD NAME="createdby" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="userid of person who created this question" PREVIOUS="timemodified" NEXT="modifiedby"/>
-        <FIELD NAME="modifiedby" TYPE="int" LENGTH="10" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="userid of person who last edited this question" PREVIOUS="createdby"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="category"/>
-        <KEY NAME="category" TYPE="foreign" FIELDS="category" REFTABLE="question_categories" REFFIELDS="id" PREVIOUS="primary" NEXT="parent"/>
-        <KEY NAME="parent" TYPE="foreign" FIELDS="parent" REFTABLE="question" REFFIELDS="id" COMMENT="note that to make this recursive FK working someday, the parent field must be declared NULL" PREVIOUS="category" NEXT="createdby"/>
-        <KEY NAME="createdby" TYPE="foreign" FIELDS="createdby" REFTABLE="user" REFFIELDS="id" COMMENT="foreign (createdby) references user (id)" PREVIOUS="parent" NEXT="modifiedby"/>
-        <KEY NAME="modifiedby" TYPE="foreign" FIELDS="modifiedby" REFTABLE="user" REFFIELDS="id" COMMENT="foreign (modifiedby) references user (id)" PREVIOUS="createdby"/>
-      </KEYS>
-    </TABLE>
-    <TABLE NAME="question_answers" COMMENT="Answers, with a fractional grade (0-1) and feedback" PREVIOUS="question" NEXT="question_dataset_definitions">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
-        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="answer"/>
-        <FIELD NAME="answer" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="fraction"/>
-        <FIELD NAME="fraction" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answer" NEXT="feedback"/>
-        <FIELD NAME="feedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="fraction"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
-        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary"/>
-      </KEYS>
-    </TABLE>
-    <TABLE NAME="question_dataset_definitions" COMMENT="Organises and stores properties for dataset items" PREVIOUS="question_answers" NEXT="question_dataset_items">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="category"/>
-        <FIELD NAME="category" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="name"/>
-        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="category" NEXT="type"/>
-        <FIELD NAME="type" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="name" NEXT="options"/>
-        <FIELD NAME="options" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="type" NEXT="itemcount"/>
-        <FIELD NAME="itemcount" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="options"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="category"/>
-        <KEY NAME="category" TYPE="foreign" FIELDS="category" REFTABLE="question_categories" REFFIELDS="id" PREVIOUS="primary"/>
-      </KEYS>
-    </TABLE>
-    <TABLE NAME="question_dataset_items" COMMENT="Individual dataset items" PREVIOUS="question_dataset_definitions" NEXT="question_datasets">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="definition"/>
-        <FIELD NAME="definition" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="itemnumber"/>
-        <FIELD NAME="itemnumber" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="definition" NEXT="value"/>
-        <FIELD NAME="value" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="itemnumber"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
-      </KEYS>
-      <INDEXES>
-        <INDEX NAME="definition" UNIQUE="false" FIELDS="definition"/>
-      </INDEXES>
-    </TABLE>
-    <TABLE NAME="question_datasets" COMMENT="Many-many relation between questions and dataset definitions" PREVIOUS="question_dataset_items" NEXT="question_numerical_units">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
-        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="datasetdefinition"/>
-        <FIELD NAME="datasetdefinition" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
-        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary" NEXT="datasetdefinition"/>
-        <KEY NAME="datasetdefinition" TYPE="foreign" FIELDS="datasetdefinition" REFTABLE="question_dataset_definitions" REFFIELDS="id" PREVIOUS="question"/>
-      </KEYS>
-      <INDEXES>
-        <INDEX NAME="question-datasetdefinition" UNIQUE="false" FIELDS="question, datasetdefinition"/>
-      </INDEXES>
-    </TABLE>
-    <TABLE NAME="question_numerical_units" COMMENT="Optional unit options for numerical questions" PREVIOUS="question_datasets" NEXT="question_attempts">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
-        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="multiplier"/>
-        <FIELD NAME="multiplier" TYPE="number" LENGTH="40" NOTNULL="true" UNSIGNED="false" DEFAULT="1.00000000000000000000" SEQUENCE="false" ENUM="false" DECIMALS="20" PREVIOUS="question" NEXT="unit"/>
-        <FIELD NAME="unit" TYPE="char" LENGTH="50" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="multiplier"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
-        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary"/>
-      </KEYS>
-      <INDEXES>
-        <INDEX NAME="question-unit" UNIQUE="true" FIELDS="question, unit" COMMENT="Unique index to ensure that only one unit with a particular name is created for each question."/>
-      </INDEXES>
-    </TABLE>
-    <TABLE NAME="question_attempts" COMMENT="Student attempts. This table gets extended by the modules" PREVIOUS="question_numerical_units" NEXT="question_states">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="modulename"/>
-        <FIELD NAME="modulename" TYPE="char" LENGTH="20" NOTNULL="true" DEFAULT="quiz" SEQUENCE="false" ENUM="false" PREVIOUS="id"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
-      </KEYS>
-    </TABLE>
-    <TABLE NAME="question_states" COMMENT="Stores user responses to an attempt, and percentage grades" PREVIOUS="question_attempts" NEXT="question_sessions">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="attempt"/>
-        <FIELD NAME="attempt" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="question"/>
-        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="attempt" NEXT="originalquestion"/>
-        <FIELD NAME="originalquestion" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="seq_number"/>
-        <FIELD NAME="seq_number" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="originalquestion" NEXT="answer"/>
-        <FIELD NAME="answer" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="seq_number" NEXT="timestamp"/>
-        <FIELD NAME="timestamp" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answer" NEXT="event"/>
-        <FIELD NAME="event" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timestamp" NEXT="grade"/>
-        <FIELD NAME="grade" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="event" NEXT="raw_grade"/>
-        <FIELD NAME="raw_grade" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="grade" NEXT="penalty"/>
-        <FIELD NAME="penalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="raw_grade"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="attempt"/>
-        <KEY NAME="attempt" TYPE="foreign" FIELDS="attempt" REFTABLE="question_attempts" REFFIELDS="id" PREVIOUS="primary" NEXT="question"/>
-        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="attempt"/>
-      </KEYS>
-    </TABLE>
-    <TABLE NAME="question_sessions" COMMENT="Gives ids of the newest open and newest graded states" PREVIOUS="question_states" NEXT="quiz">
-      <FIELDS>
-        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="attemptid"/>
-        <FIELD NAME="attemptid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="questionid"/>
-        <FIELD NAME="questionid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="attemptid" NEXT="newest"/>
-        <FIELD NAME="newest" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="questionid" NEXT="newgraded"/>
-        <FIELD NAME="newgraded" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="newest" NEXT="sumpenalty"/>
-        <FIELD NAME="sumpenalty" TYPE="float" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="newgraded" NEXT="manualcomment"/>
-        <FIELD NAME="manualcomment" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="sumpenalty"/>
-      </FIELDS>
-      <KEYS>
-        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="attemptid"/>
-        <KEY NAME="attemptid" TYPE="foreign" FIELDS="attemptid" REFTABLE="question_attempts" REFFIELDS="id" PREVIOUS="primary" NEXT="questionid"/>
-        <KEY NAME="questionid" TYPE="foreign" FIELDS="questionid" REFTABLE="question" REFFIELDS="id" PREVIOUS="attemptid" NEXT="newest"/>
-        <KEY NAME="newest" TYPE="foreign" FIELDS="newest" REFTABLE="question_states" REFFIELDS="id" PREVIOUS="questionid" NEXT="newgraded"/>
-        <KEY NAME="newgraded" TYPE="foreign" FIELDS="newgraded" REFTABLE="question_states" REFFIELDS="id" PREVIOUS="newest"/>
-      </KEYS>
-      <INDEXES>
-        <INDEX NAME="attemptid-questionid" UNIQUE="true" FIELDS="attemptid, questionid"/>
-      </INDEXES>
-    </TABLE>
-    <TABLE NAME="quiz" COMMENT="Main information about each quiz" PREVIOUS="question_sessions" NEXT="quiz_attempts">
+    <TABLE NAME="quiz" COMMENT="Main information about each quiz" NEXT="quiz_attempts">
       <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="name"/>
diff --git a/question/type/calculated/db/install.xml b/question/type/calculated/db/install.xml
index 9f7ac7e1bf..fec81addfd 100644
--- a/question/type/calculated/db/install.xml
+++ b/question/type/calculated/db/install.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="question/type/calculated/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/calculated">
+<XMLDB PATH="question/type/calculated/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/calculated. This question type also relies on the question_numerical_units table created by the numerical question type, and the tables created by the datasetdependent question type base class.">
   <TABLES>
     <TABLE NAME="question_calculated" COMMENT="Options for questions of type calculated">
       <FIELDS>
diff --git a/question/type/datasetdependent/db/install.xml b/question/type/datasetdependent/db/install.xml
new file mode 100644
index 0000000000..c24b425438
--- /dev/null
+++ b/question/type/datasetdependent/db/install.xml
@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<XMLDB PATH="question/type/calculated/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/calculated">
+  <TABLES>
+    <TABLE NAME="question_dataset_definitions" COMMENT="Organises and stores properties for dataset items" NEXT="question_dataset_items">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="category"/>
+        <FIELD NAME="category" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="name"/>
+        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="category" NEXT="type"/>
+        <FIELD NAME="type" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="name" NEXT="options"/>
+        <FIELD NAME="options" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="type" NEXT="itemcount"/>
+        <FIELD NAME="itemcount" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="options"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="category"/>
+        <KEY NAME="category" TYPE="foreign" FIELDS="category" REFTABLE="question_categories" REFFIELDS="id" PREVIOUS="primary"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="question_dataset_items" COMMENT="Individual dataset items" PREVIOUS="question_dataset_definitions" NEXT="question_datasets">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="definition"/>
+        <FIELD NAME="definition" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="itemnumber"/>
+        <FIELD NAME="itemnumber" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="definition" NEXT="value"/>
+        <FIELD NAME="value" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="itemnumber"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
+      </KEYS>
+      <INDEXES>
+        <INDEX NAME="definition" UNIQUE="false" FIELDS="definition"/>
+      </INDEXES>
+    </TABLE>
+    <TABLE NAME="question_datasets" COMMENT="Many-many relation between questions and dataset definitions" PREVIOUS="question_dataset_items">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="datasetdefinition"/>
+        <FIELD NAME="datasetdefinition" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
+        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary" NEXT="datasetdefinition"/>
+        <KEY NAME="datasetdefinition" TYPE="foreign" FIELDS="datasetdefinition" REFTABLE="question_dataset_definitions" REFFIELDS="id" PREVIOUS="question"/>
+      </KEYS>
+      <INDEXES>
+        <INDEX NAME="question-datasetdefinition" UNIQUE="false" FIELDS="question, datasetdefinition"/>
+      </INDEXES>
+    </TABLE>
+  </TABLES>
+</XMLDB>
diff --git a/question/type/datasetdependent/db/upgrade.php b/question/type/datasetdependent/db/upgrade.php
new file mode 100644
index 0000000000..d3017c7368
--- /dev/null
+++ b/question/type/datasetdependent/db/upgrade.php
@@ -0,0 +1,38 @@
+<?php  // $Id$
+
+// This file keeps track of upgrades to 
+// the datasetdependent abstract qtype plugin
+//
+// Sometimes, changes between versions involve
+// alterations to database structures and other
+// major things that may break installations.
+//
+// The upgrade function in this file will attempt
+// to perform all the necessary actions to upgrade
+// your older installtion to the current version.
+//
+// If there's something it cannot do itself, it
+// will tell you what you need to do.
+//
+// The commands in here will all be database-neutral,
+// using the methods of database_manager class
+
+function xmldb_qtype_datasetdependent_upgrade($oldversion=0) {
+
+    global $CFG, $THEME, $DB;
+
+    $result = true;
+
+/// And upgrade begins here. For each one, you'll need one 
+/// block of code similar to the next one. Please, delete 
+/// this comment lines once this file start handling proper
+/// upgrade code.
+
+/// if ($result && $oldversion < YYYYMMDD00) { //New version in version.php
+///     $result = result of database_manager methods
+/// }
+
+    return $result;
+}
+
+?>
diff --git a/question/type/numerical/db/install.xml b/question/type/numerical/db/install.xml
index c06857c956..7c350d5893 100644
--- a/question/type/numerical/db/install.xml
+++ b/question/type/numerical/db/install.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <XMLDB PATH="question/type/numerical/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/numerical">
   <TABLES>
-    <TABLE NAME="question_numerical" COMMENT="Options for numerical questions">
+    <TABLE NAME="question_numerical" COMMENT="Options for numerical questions" NEXT="question_numerical_units">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
         <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="answer"/>
@@ -16,5 +16,20 @@
         <INDEX NAME="answer" UNIQUE="false" FIELDS="answer"/>
       </INDEXES>
     </TABLE>
+    <TABLE NAME="question_numerical_units" COMMENT="Optional unit options for numerical questions" PREVIOUS="question_numerical">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="multiplier"/>
+        <FIELD NAME="multiplier" TYPE="number" LENGTH="40" NOTNULL="true" UNSIGNED="false" DEFAULT="1.00000000000000000000" SEQUENCE="false" ENUM="false" DECIMALS="20" PREVIOUS="question" NEXT="unit"/>
+        <FIELD NAME="unit" TYPE="char" LENGTH="50" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="multiplier"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
+        <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="primary"/>
+      </KEYS>
+      <INDEXES>
+        <INDEX NAME="question-unit" UNIQUE="true" FIELDS="question, unit" COMMENT="Unique index to ensure that only one unit with a particular name is created for each question."/>
+      </INDEXES>
+    </TABLE>
   </TABLES>
 </XMLDB>
-- 
2.39.5