From 26574bbad77d07e7d37827fd4018351f49c61501 Mon Sep 17 00:00:00 2001
From: tjhunt <tjhunt>
Date: Thu, 5 Mar 2009 11:24:41 +0000
Subject: [PATCH] quiz/questions: Improve documentation of database tables.

---
 mod/quiz/db/install.xml                    | 106 ++++++++++-----------
 question/type/multichoice/db/install.xml   |  16 ++--
 question/type/numerical/db/install.xml     |  21 ++--
 question/type/randomsamatch/db/install.xml |   9 +-
 question/type/shortanswer/db/install.xml   |  11 ++-
 question/type/truefalse/db/install.xml     |  11 ++-
 6 files changed, 93 insertions(+), 81 deletions(-)

diff --git a/mod/quiz/db/install.xml b/mod/quiz/db/install.xml
index ea2bfae425..33dddfee69 100755
--- a/mod/quiz/db/install.xml
+++ b/mod/quiz/db/install.xml
@@ -7,32 +7,32 @@
     <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"/>
-        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="course" NEXT="intro"/>
-        <FIELD NAME="intro" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="name" NEXT="timeopen"/>
-        <FIELD NAME="timeopen" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="intro" NEXT="timeclose"/>
-        <FIELD NAME="timeclose" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timeopen" NEXT="optionflags"/>
-        <FIELD NAME="optionflags" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timeclose" NEXT="penaltyscheme"/>
-        <FIELD NAME="penaltyscheme" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="optionflags" NEXT="attempts"/>
-        <FIELD NAME="attempts" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="penaltyscheme" NEXT="attemptonlast"/>
-        <FIELD NAME="attemptonlast" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="attempts" NEXT="grademethod"/>
-        <FIELD NAME="grademethod" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="attemptonlast" NEXT="decimalpoints"/>
-        <FIELD NAME="decimalpoints" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="2" SEQUENCE="false" ENUM="false" PREVIOUS="grademethod" NEXT="review"/>
-        <FIELD NAME="review" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="decimalpoints" NEXT="questionsperpage"/>
-        <FIELD NAME="questionsperpage" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="review" NEXT="shufflequestions"/>
-        <FIELD NAME="shufflequestions" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="questionsperpage" NEXT="shuffleanswers"/>
-        <FIELD NAME="shuffleanswers" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="shufflequestions" NEXT="questions"/>
-        <FIELD NAME="questions" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="shuffleanswers" NEXT="sumgrades"/>
-        <FIELD NAME="sumgrades" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="questions" NEXT="grade"/>
-        <FIELD NAME="grade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="sumgrades" NEXT="timecreated"/>
-        <FIELD NAME="timecreated" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="grade" NEXT="timemodified"/>
-        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timecreated" NEXT="timelimit"/>
-        <FIELD NAME="timelimit" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timemodified" NEXT="password"/>
-        <FIELD NAME="password" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="timelimit" NEXT="subnet"/>
-        <FIELD NAME="subnet" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="password" NEXT="popup"/>
-        <FIELD NAME="popup" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="subnet" NEXT="delay1"/>
-        <FIELD NAME="delay1" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="popup" NEXT="delay2"/>
-        <FIELD NAME="delay2" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="delay1" NEXT="showuserpicture"/>
+        <FIELD NAME="course" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references course.id." PREVIOUS="id" NEXT="name"/>
+        <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="The name of this quiz." PREVIOUS="course" NEXT="intro"/>
+        <FIELD NAME="intro" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="The introductory text desplayed on the view.php page." PREVIOUS="name" NEXT="timeopen"/>
+        <FIELD NAME="timeopen" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Time at which students may start attempting this quiz." PREVIOUS="intro" NEXT="timeclose"/>
+        <FIELD NAME="timeclose" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Time by which students must have completed their attempt." PREVIOUS="timeopen" NEXT="optionflags"/>
+        <FIELD NAME="optionflags" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="This stores the adaptive mode setting for this quiz." PREVIOUS="timeclose" NEXT="penaltyscheme"/>
+        <FIELD NAME="penaltyscheme" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Stores the apply penaties setting." PREVIOUS="optionflags" NEXT="attempts"/>
+        <FIELD NAME="attempts" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The maximum number of attempts that a student is allowed at this quiz. 0 mean no limit." PREVIOUS="penaltyscheme" NEXT="attemptonlast"/>
+        <FIELD NAME="attemptonlast" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Whether each attempt builds on last mode is on." PREVIOUS="attempts" NEXT="grademethod"/>
+        <FIELD NAME="grademethod" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="1" SEQUENCE="false" ENUM="false" COMMENT="How individual attempt grades are combined to get the overall grade. From the top of mod/quiz/lib.php: 1 = QUIZ_GRADEHIGHEST, 2 = QUIZ_GRADEAVERAGE, 3 = QUIZ_ATTEMPTFIRST, 4 = QUIZ_ATTEMPTLAST." PREVIOUS="attemptonlast" NEXT="decimalpoints"/>
+        <FIELD NAME="decimalpoints" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="2" SEQUENCE="false" ENUM="false" COMMENT="Number of decimal points to display when printing scores belonging to this quiz." PREVIOUS="grademethod" NEXT="review"/>
+        <FIELD NAME="review" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="A bitfield encoding the Review options setting. Read the code of function quiz_get_reviewoptions from mod/quiz/locallib.php to see what each bit means." PREVIOUS="decimalpoints" NEXT="questionsperpage"/>
+        <FIELD NAME="questionsperpage" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="This does not do exactly what the name suggests, and the behaviour depends on the shufflequestions setting." PREVIOUS="review" NEXT="shufflequestions"/>
+        <FIELD NAME="shufflequestions" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Whether the list of questions in the quiz should be randomly shuffled at the start of each attempt." PREVIOUS="questionsperpage" NEXT="shuffleanswers"/>
+        <FIELD NAME="shuffleanswers" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Whether, in question types that support it, individual parts of a question should be shuffled." PREVIOUS="shufflequestions" NEXT="questions"/>
+        <FIELD NAME="questions" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Comma-separated list of questionids, with 0s for page breaks. The layout of questions in this quiz." PREVIOUS="shuffleanswers" NEXT="sumgrades"/>
+        <FIELD NAME="sumgrades" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="Total of the maximum grades you can get from each question. This is redundant, it is SELECT SUM(grade) FROM {quiz_question_instances} WHERE quiz = ?." PREVIOUS="questions" NEXT="grade"/>
+        <FIELD NAME="grade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="Maximum grade that you can get from this quiz." PREVIOUS="sumgrades" NEXT="timecreated"/>
+        <FIELD NAME="timecreated" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Timestamp when this quiz was created." PREVIOUS="grade" NEXT="timemodified"/>
+        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Timestamp when this row was last updated." PREVIOUS="timecreated" NEXT="timelimit"/>
+        <FIELD NAME="timelimit" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Time limit in minutes. (This should really be changed to seconds for consistency.)" PREVIOUS="timemodified" NEXT="password"/>
+        <FIELD NAME="password" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Students must enter this password before they can attempt the quiz." PREVIOUS="timelimit" NEXT="subnet"/>
+        <FIELD NAME="subnet" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="If set, only allow attempts from certain IP addresses. The checking is performed by the address_in_subnet function from lib/moodlelib.php." PREVIOUS="password" NEXT="popup"/>
+        <FIELD NAME="popup" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Force the quiz to be attempted in a full-screen pop-up window with some evil JavaScript that attempts to prevent copying and pasting, etc." PREVIOUS="subnet" NEXT="delay1"/>
+        <FIELD NAME="delay1" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Enforced delay between the first and second attempts, in seconds." PREVIOUS="popup" NEXT="delay2"/>
+        <FIELD NAME="delay2" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Enforced delay between the second and subsequent attempts, in seconds." PREVIOUS="delay1" NEXT="showuserpicture"/>
         <FIELD NAME="showuserpicture" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Option to show the user's picture during the attempt and on the review page." PREVIOUS="delay2"/>
       </FIELDS>
       <KEYS>
@@ -45,16 +45,16 @@
     <TABLE NAME="quiz_attempts" COMMENT="Stores various attempts on a quiz" PREVIOUS="quiz" NEXT="quiz_grades">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="uniqueid"/>
-        <FIELD NAME="uniqueid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="quiz"/>
-        <FIELD NAME="quiz" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="uniqueid" NEXT="userid"/>
-        <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="quiz" NEXT="attempt"/>
-        <FIELD NAME="attempt" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="userid" NEXT="sumgrades"/>
-        <FIELD NAME="sumgrades" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="attempt" NEXT="timestart"/>
-        <FIELD NAME="timestart" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="sumgrades" NEXT="timefinish"/>
-        <FIELD NAME="timefinish" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timestart" NEXT="timemodified"/>
-        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="timefinish" NEXT="layout"/>
-        <FIELD NAME="layout" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="timemodified" NEXT="preview"/>
-        <FIELD NAME="preview" TYPE="int" LENGTH="3" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="layout"/>
+        <FIELD NAME="uniqueid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question_attempts.id, and hence links into the attempt information for each question in the attempt." PREVIOUS="id" NEXT="quiz"/>
+        <FIELD NAME="quiz" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references quiz.id." PREVIOUS="uniqueid" NEXT="userid"/>
+        <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references user.id." PREVIOUS="quiz" NEXT="attempt"/>
+        <FIELD NAME="attempt" TYPE="int" LENGTH="6" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The attempt number for this user on this quiz. It counts up from one. (quiz, userid, attempt) could be an alternate primary key for this table." PREVIOUS="userid" NEXT="sumgrades"/>
+        <FIELD NAME="sumgrades" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="The sum of the user's grades for all questions in this attempt." PREVIOUS="attempt" NEXT="timestart"/>
+        <FIELD NAME="timestart" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The time this attempt started." PREVIOUS="sumgrades" NEXT="timefinish"/>
+        <FIELD NAME="timefinish" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The time this attempt finished. If 0, this attempt is still open." PREVIOUS="timestart" NEXT="timemodified"/>
+        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The time this attemtp was last modified. I think this is not changed by a regrade, and I don't know about what happens if a teacher manually grades a question. If you really need to know, look at the code, then update this comment. Thanks." PREVIOUS="timefinish" NEXT="layout"/>
+        <FIELD NAME="layout" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="A comma-separated list of question ids, with 0s for page breaks. If quiz.shuffequestions = 0, this will be the same as quiz.layout." PREVIOUS="timemodified" NEXT="preview"/>
+        <FIELD NAME="preview" TYPE="int" LENGTH="3" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Used to distinguish preview attempts. Previews do not show up in reports; are deleted automatically when quiz settings are changed; and do not prevent the quiz from being edited." PREVIOUS="layout"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="uniqueid"/>
@@ -65,13 +65,13 @@
         <INDEX NAME="userid" UNIQUE="false" FIELDS="userid"/>
       </INDEXES>
     </TABLE>
-    <TABLE NAME="quiz_grades" COMMENT="Final quiz grade (may be best of several attempts)" PREVIOUS="quiz_attempts" NEXT="quiz_question_instances">
+    <TABLE NAME="quiz_grades" COMMENT="The overall grade for each user on the quiz, based on their individual and the quiz.grademethod setting." PREVIOUS="quiz_attempts" NEXT="quiz_question_instances">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="quiz"/>
-        <FIELD NAME="quiz" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="userid"/>
-        <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="quiz" NEXT="grade"/>
-        <FIELD NAME="grade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="userid" NEXT="timemodified"/>
-        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="grade"/>
+        <FIELD NAME="quiz" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references quiz.id." PREVIOUS="id" NEXT="userid"/>
+        <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references user.id." PREVIOUS="quiz" NEXT="grade"/>
+        <FIELD NAME="grade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The overall grade from the quiz. Not affected by overrides in the gradebook." DECIMALS="5" PREVIOUS="userid" NEXT="timemodified"/>
+        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="The last time this grade changed." PREVIOUS="grade"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="quiz"/>
@@ -81,12 +81,12 @@
         <INDEX NAME="userid" UNIQUE="false" FIELDS="userid"/>
       </INDEXES>
     </TABLE>
-    <TABLE NAME="quiz_question_instances" COMMENT="The grade for a question in a quiz" PREVIOUS="quiz_grades" NEXT="quiz_feedback">
+    <TABLE NAME="quiz_question_instances" COMMENT="Stores the maximum possible grade (weight) for each question used in a quiz." PREVIOUS="quiz_grades" NEXT="quiz_feedback">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="quiz"/>
-        <FIELD NAME="quiz" 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="quiz" NEXT="grade"/>
-        <FIELD NAME="grade" TYPE="number" LENGTH="12" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="7" PREVIOUS="question"/>
+        <FIELD NAME="quiz" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references quiz.id." PREVIOUS="id" NEXT="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id." PREVIOUS="quiz" NEXT="grade"/>
+        <FIELD NAME="grade" TYPE="number" LENGTH="12" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="7" COMMENT="How many marks this question contributes to quiz.sumgrades." PREVIOUS="question"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="quiz"/>
@@ -94,27 +94,27 @@
         <KEY NAME="question" TYPE="foreign" FIELDS="question" REFTABLE="question" REFFIELDS="id" PREVIOUS="quiz"/>
       </KEYS>
     </TABLE>
-    <TABLE NAME="quiz_feedback" COMMENT="Feedback given to students based on their overall score on the test" PREVIOUS="quiz_question_instances" NEXT="quiz_report">
+    <TABLE NAME="quiz_feedback" COMMENT="Feedback given to students based on which grade band their overall score lies." PREVIOUS="quiz_question_instances" NEXT="quiz_report">
       <FIELDS>
         <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="quizid"/>
-        <FIELD NAME="quizid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="feedbacktext"/>
-        <FIELD NAME="feedbacktext" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="quizid" NEXT="mingrade"/>
-        <FIELD NAME="mingrade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="feedbacktext" NEXT="maxgrade"/>
-        <FIELD NAME="maxgrade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="mingrade"/>
+        <FIELD NAME="quizid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references quiz.id." PREVIOUS="id" NEXT="feedbacktext"/>
+        <FIELD NAME="feedbacktext" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="The feedback to show for a attempt where mingrade &lt;= attempt grade &lt; maxgrade. See function quiz_feedback_for_grade in mod/quiz/locallib.php." PREVIOUS="quizid" NEXT="mingrade"/>
+        <FIELD NAME="mingrade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="The lower limit of this grade band. Inclusive." PREVIOUS="feedbacktext" NEXT="maxgrade"/>
+        <FIELD NAME="maxgrade" TYPE="number" LENGTH="10" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" DECIMALS="5" COMMENT="The upper limit of this grade band. Exclusive." PREVIOUS="mingrade"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="quizid"/>
         <KEY NAME="quizid" TYPE="foreign" FIELDS="quizid" REFTABLE="quiz" REFFIELDS="id" PREVIOUS="primary"/>
       </KEYS>
     </TABLE>
-    <TABLE NAME="quiz_report" COMMENT="table of reports from quiz and there display order. No need to worry about deleting old records. Only records with an equivalent directory are displayed." PREVIOUS="quiz_feedback">
+    <TABLE NAME="quiz_report" COMMENT="Lists all the installed quiz reports and their display order and so on. No need to worry about deleting old records. Only records with an equivalent directory are displayed." PREVIOUS="quiz_feedback">
       <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="false" SEQUENCE="false" ENUM="false" COMMENT="name of the report, same as the directory name" PREVIOUS="id" NEXT="displayorder"/>
         <FIELD NAME="displayorder" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="display order for report tabs" PREVIOUS="name" NEXT="lastcron"/>
-        <FIELD NAME="lastcron" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="displayorder" NEXT="cron"/>
+        <FIELD NAME="lastcron" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="timestamp when cron was last run for this report." PREVIOUS="displayorder" NEXT="cron"/>
         <FIELD NAME="cron" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="0 if there is no cron for this report (default) or the time between crons otherwise." PREVIOUS="lastcron" NEXT="capability"/>
-        <FIELD NAME="capability" TYPE="char" LENGTH="255" NOTNULL="false" SEQUENCE="false" ENUM="false" PREVIOUS="cron"/>
+        <FIELD NAME="capability" TYPE="char" LENGTH="255" NOTNULL="false" SEQUENCE="false" ENUM="false" COMMENT="Capability required to see this report. May be blank which means use the default of mod/quiz:viewreport. This is used when deciding which tabs to render." PREVIOUS="cron"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
diff --git a/question/type/multichoice/db/install.xml b/question/type/multichoice/db/install.xml
index 0c3183a718..c3ea52d111 100644
--- a/question/type/multichoice/db/install.xml
+++ b/question/type/multichoice/db/install.xml
@@ -7,14 +7,14 @@
     <TABLE NAME="question_multichoice" COMMENT="Options for multiple choice questions">
       <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="layout"/>
-        <FIELD NAME="layout" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="answers"/>
-        <FIELD NAME="answers" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="layout" NEXT="single"/>
-        <FIELD NAME="single" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answers" NEXT="shuffleanswers"/>
-        <FIELD NAME="shuffleanswers" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="1" SEQUENCE="false" ENUM="false" PREVIOUS="single" NEXT="correctfeedback"/>
-        <FIELD NAME="correctfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="shuffleanswers" NEXT="partiallycorrectfeedback"/>
-        <FIELD NAME="partiallycorrectfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="correctfeedback" NEXT="incorrectfeedback"/>
-        <FIELD NAME="incorrectfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="partiallycorrectfeedback" NEXT="answernumbering"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id" PREVIOUS="id" NEXT="layout"/>
+        <FIELD NAME="layout" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Not used. Was intended for a vertical/horizontal layout option. See MDL-18445." PREVIOUS="question" NEXT="answers"/>
+        <FIELD NAME="answers" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Redundant. Comma-separated list of question_answer ids. SELECT id FROM question_answers WHERE question = ? ORDER BY id." PREVIOUS="layout" NEXT="single"/>
+        <FIELD NAME="single" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="If 0 it multiple response (checkboxes). Otherwise it is radio buttons." PREVIOUS="answers" NEXT="shuffleanswers"/>
+        <FIELD NAME="shuffleanswers" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="false" DEFAULT="1" SEQUENCE="false" ENUM="false" COMMENT="Whether the choices can be randomly shuffled." PREVIOUS="single" NEXT="correctfeedback"/>
+        <FIELD NAME="correctfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Feedback shown for any correct response." PREVIOUS="shuffleanswers" NEXT="partiallycorrectfeedback"/>
+        <FIELD NAME="partiallycorrectfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Feedback shown for any partially correct response." PREVIOUS="correctfeedback" NEXT="incorrectfeedback"/>
+        <FIELD NAME="incorrectfeedback" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Feedback shown for any incorrect response." PREVIOUS="partiallycorrectfeedback" NEXT="answernumbering"/>
         <FIELD NAME="answernumbering" TYPE="char" LENGTH="10" NOTNULL="true" DEFAULT="abc" SEQUENCE="false" ENUM="false" COMMENT="Indicates how and whether the choices should be numbered." PREVIOUS="incorrectfeedback"/>
       </FIELDS>
       <KEYS>
diff --git a/question/type/numerical/db/install.xml b/question/type/numerical/db/install.xml
index 81223fd3e6..c2eef1699b 100644
--- a/question/type/numerical/db/install.xml
+++ b/question/type/numerical/db/install.xml
@@ -1,12 +1,15 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="question/type/numerical/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/numerical">
+<XMLDB PATH="question/type/numerical/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/numerical"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="../../../../lib/xmldb/xmldb.xsd"
+>
   <TABLES>
-    <TABLE NAME="question_numerical" COMMENT="Options for numerical questions" NEXT="question_numerical_units">
+    <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"/>
-        <FIELD NAME="answer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="tolerance"/>
-        <FIELD NAME="tolerance" TYPE="char" LENGTH="255" NOTNULL="true" DEFAULT="0.0" SEQUENCE="false" ENUM="false" PREVIOUS="answer"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Redundant, because of the answer field. Foreign key references question.id." PREVIOUS="id" NEXT="answer"/>
+        <FIELD NAME="answer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question_answers.id." PREVIOUS="question" NEXT="tolerance"/>
+        <FIELD NAME="tolerance" TYPE="char" LENGTH="255" NOTNULL="true" DEFAULT="0.0" SEQUENCE="false" ENUM="false" COMMENT="Allowed error when matching a response to this answer. I don't know why this is stored as a string." PREVIOUS="answer"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
@@ -16,12 +19,12 @@
         <INDEX NAME="answer" UNIQUE="false" FIELDS="answer"/>
       </INDEXES>
     </TABLE>
-    <TABLE NAME="question_numerical_units" COMMENT="Optional unit options for numerical questions" PREVIOUS="question_numerical">
+    <TABLE NAME="question_numerical_units" COMMENT="Optional unit options for numerical questions. This table is also used by the calculated question type." 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"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id" PREVIOUS="id" NEXT="multiplier"/>
+        <FIELD NAME="multiplier" TYPE="number" LENGTH="40" NOTNULL="true" UNSIGNED="false" DEFAULT="1.00000000000000000000" SEQUENCE="false" ENUM="false" DECIMALS="20" COMMENT="The multiplier for this unit. For example, if the first unit is (1.0, 'cm'), another unit might be (0.1, 'mm') or (100.0, 'm')." PREVIOUS="question" NEXT="unit"/>
+        <FIELD NAME="unit" TYPE="char" LENGTH="50" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="The unit. For example 'm' or 'kg'." PREVIOUS="multiplier"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
diff --git a/question/type/randomsamatch/db/install.xml b/question/type/randomsamatch/db/install.xml
index 9500076eed..d96837d811 100644
--- a/question/type/randomsamatch/db/install.xml
+++ b/question/type/randomsamatch/db/install.xml
@@ -1,11 +1,14 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="question/type/randomsamatch/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/randomsamatch">
+<XMLDB PATH="question/type/randomsamatch/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/randomsamatch"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="../../../../lib/xmldb/xmldb.xsd"
+>
   <TABLES>
     <TABLE NAME="question_randomsamatch" COMMENT="Info about a random short-answer matching question">
       <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="choose"/>
-        <FIELD NAME="choose" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="4" SEQUENCE="false" ENUM="false" PREVIOUS="question"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id." PREVIOUS="id" NEXT="choose"/>
+        <FIELD NAME="choose" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="4" SEQUENCE="false" ENUM="false" COMMENT="Number of subquestions to randomly generate." PREVIOUS="question"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
diff --git a/question/type/shortanswer/db/install.xml b/question/type/shortanswer/db/install.xml
index f6e4030349..59cb529f84 100644
--- a/question/type/shortanswer/db/install.xml
+++ b/question/type/shortanswer/db/install.xml
@@ -1,12 +1,15 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="question/type/shortanswer/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/shortanswer">
+<XMLDB PATH="question/type/shortanswer/db" VERSION="20090305" COMMENT="XMLDB file for Moodle question/type/shortanswer"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="../../../../lib/xmldb/xmldb.xsd"
+>
   <TABLES>
     <TABLE NAME="question_shortanswer" COMMENT="Options for short answer questions">
       <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="answers"/>
-        <FIELD NAME="answers" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="usecase"/>
-        <FIELD NAME="usecase" TYPE="int" LENGTH="2" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="answers"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id." PREVIOUS="id" NEXT="answers"/>
+        <FIELD NAME="answers" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" ENUM="false" COMMENT="Redundant. Comma-separated list of question_answer ids. SELECT id FROM question_answers WHERE question = ? ORDER BY id." PREVIOUS="question" NEXT="usecase"/>
+        <FIELD NAME="usecase" TYPE="int" LENGTH="2" NOTNULL="true" UNSIGNED="false" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Whether answers are matched case-sensitively." PREVIOUS="answers"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
diff --git a/question/type/truefalse/db/install.xml b/question/type/truefalse/db/install.xml
index 8e259f13fe..e34649d76f 100644
--- a/question/type/truefalse/db/install.xml
+++ b/question/type/truefalse/db/install.xml
@@ -1,12 +1,15 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="question/type/truefalse/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/truefalse">
+<XMLDB PATH="question/type/truefalse/db" VERSION="20060812" COMMENT="XMLDB file for Moodle question/type/truefalse"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="../../../../lib/xmldb/xmldb.xsd"
+>
   <TABLES>
     <TABLE NAME="question_truefalse" COMMENT="Options for True-False questions">
       <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="trueanswer"/>
-        <FIELD NAME="trueanswer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="question" NEXT="falseanswer"/>
-        <FIELD NAME="falseanswer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" PREVIOUS="trueanswer"/>
+        <FIELD NAME="question" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question.id." PREVIOUS="id" NEXT="trueanswer"/>
+        <FIELD NAME="trueanswer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question_answers.id. The 'True' choice." PREVIOUS="question" NEXT="falseanswer"/>
+        <FIELD NAME="falseanswer" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" ENUM="false" COMMENT="Foreign key references question_answers.id. The 'False' choice." PREVIOUS="trueanswer"/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" NEXT="question"/>
-- 
2.39.5