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<!DOCTYPE html>
<HTML>
<HEAD>
<title>Corrections to TLA+ Video Course</title>
<STYLE type="text/css">
body { background-color: #e4e4e4; max-width:700px;
font-family:Calibri,Trebuchet MS,Verdana,sans-serif;
font-size:18px; margin-left:15px}
H1 {margin-bottom:0px}
H2 {line-height:45px; margin-bottom:0px; text-align: left; font-size:26px;
color:#000000}
H3 {line-height:10px; margin-bottom:12px; margin-top:20px;
text-align: left}
UL {margin-top:-10px}
LI {margin-top:15px}
td {padding-left:-5px; padding-right:0px}
code {font-size:17px; margin:2px }
</STYLE>
</HEAD>
<body>
<h1>Corrections to the TLA+ Video Course</h1>
<i>Last modified 13 August 2021</i>
<hr>
<p>
This page lists corrections for all known problems with
the content of
<a href="../videos.html">The TLA+ Video Course</a>.
Problems in the videos include errors, misleading or hard to
understand parts, and obsolete information. They are identified
by minutes:seconds into the video where the problem begins.
Not addressed are problems with video quality, trouble downloading the
videos, or bad acting.
</p>
<p style="margin-top:30px"></p>
<h3><A name="lecture1">Lecture 1. Introduction to TLA<sup>+</sup></a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
13:16
</td>
<td>
The word <q>possible</q> should be followed by <q>behaviors</q>.
</td>
</tr>
</table>
<h3><A name="lecture3">Lecture 3. Two-Phase Commit</a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>0:34
</td>
<td>
The TLA+ web site has been completely changed since the video was
made. The URL of the home page is the same, but resources for
learning about TLA+ are found by clicking on <b>Learning TLA+</b>,
which takes you to
<a href="https://lamport.azurewebsites.net/tla/learning.html">this
page</a>.
The <i>Summary of TLA+</i> is reached from a link in the text describing by the
<i>The TLA+ Book</i> that takes you
<a href="https://lamport.azurewebsites.net/tla/summary-standalone.pdf">here</a>.
The link to <i>The TLA+ Google Group</i> is now on the <i>Learning</I> page;
it takes you
<a href="https://groups.google.com/forum/?fromgroups#!forum/tlaplus">here</a>.
</td>
</tr>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>1:56
</td>
<td>
You do not have to install Java.
Installing the Toolbox now automatically installs Java.
</td>
</tr>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>2:34
</td>
<td>
The section to check if something goes wrong is now called
<i>If You Find a Problem</i>.
</td>
</tr>
</table>
<h3><A name="lecture4">Lecture 4. Two-Phase Commit</a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
15:22
</td>
<td>
In the definition of <code>BigToSmall</code>, the formula
<code>big' = small - (3 - big)</code> should be changed to
<code>big' = big - (3 - small)</code> .
</td>
</tr>
<!-------
<tr>
<td style="vertical-align:top">
15:50
</td>
<td>
Instead of <code>TPnit</code>, the initial predicate should be
<code>TPInit</code>.
</td>
</tr>
---->
</table>
<h3><A name="lecture5">Lecture 5. Transaction Commit</a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>3:07
</td>
<td>
Ignore the spurious © symbol.
</td>
</tr>
<tr>
<td style="vertical-align:top">
18:21
</td>
<td>
The Toolbox's pages that specify a model have
changed since the video was made. If it's no longer easy to find
something on those pages from the instructions in the video, a correction
will lead you to it.
</td>
</tr>
<tr>
<td style="vertical-align:top">
20:28
</td>
<td>
The <i>Coverage</i> section of the <i>Model Checking Results</i> page
has been replaced by a section that is more helpful for beginning
users. A new profiling feature provides much more information
than the <i>Coverage</i> section did. Profiling is described in
the <i>Features</i> section of the <i>TLC Options Page</i> help page.
</td>
</tr>
</table>
<h3><A name="lecture6">Lecture 6. Two-Phase Commit</a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>4:20
</td>
<td>
Instead of just creating a new module
named <i>TwoPhase</i>, you should create a new spec by that name, which
will create that module.
</td>
</tr>
<tr>
<td style="vertical-align:top">
15:50
</td>
<td>
Instead of <code>TPnit</code>, the initial predicate should be
<code>TPInit</code>.
</td>
</tr>
</table>
<h3><A name="lecture7">Lecture 7. Paxos Commit</a></h3>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>3:42
</td>
<td>
The word <q style="margin:3px">smallest</q> in both the written and the spoken
text should be <q style="margin:3px">largest</q>.
</td>
</table>
<h3><A name="lecture8-1">Lecture 8. Implementation</a></h3>
<h4 style="margin-top:0px;margin-bottom:5px">Part 1: Preliminaries</h4>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>3:58
</td>
<td>The term <q>module-complete</q> is used here and occasionally
through 5:08 to mean <q>module-closed</q>.
</td>
</tr>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>7:11
</td>
<td>
<q>state expression</q> should be <q>action expression</q> in
<q>A state expression has a value on a step</q>.
</td>
</tr>
</table>
<h3><A name="lecture9-2">Lecture 9. The Alternating Bit Protocol</a></h3>
<h4 style="margin-top:0px;margin-bottom:5px">Part 2: The Protocol</h4>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
<font color="#e4e4e4">1</font>7:28
</td>
<td>
The <i>Advanced Options</i> page has been eliminated. The
<i>State Constraint</i> is now specified on the <i>Spec Options</I>
page, which is reached by clicking <b>Additional Spec Options</b> on
the model's <i>Model Overview</i> page.
</td>
</tr>
</table>
<h3><A name="lecture10-1">Lecture 10. Implementation with Refinement</a></h3>
<h4 style="margin-top:0px;margin-bottom:5px">Part 1: Preliminaries</h4>
<!-- Note use of <font color="#e4e4e4">1</font> to add a 1-digit space
to the time to maintain alignment.
-->
<table>
<tr>
<td style="vertical-align:top">
14:48
</td>
<td>
The formula <code>(AtoB2 < 4)
<font size=+2>∧</font> (BtoA2 < 4)</code> should be<br>
<code>(Len(AtoB2) < 4) <font size=+2>∧</font> (Len(BtoA2) < 4)</code> .
</td>
</tr>
</table>
</body> </HTML>