<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
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  <title>P1725R0: Modular Topic Design</title>
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .assertion  for assertions                    (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/******************************************************************************/
/*                                   Body                                     */
/******************************************************************************/

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;               /* limit line length to 50em for readability   */
		margin: 0 auto;                /* center text within page                     */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag     */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		/* Colors */
		color: black;
		background: white top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		color: white;
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		border-color: #c00;
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 2;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
			color: black;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			background: white;
			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;
			background: white;
		}
		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		#toc-nav > a:hover,
		#toc-nav > a:focus {
			background: #f8f8f8;
		}
		#toc-nav > a:not(:hover):not(:focus) {
			color: #707070;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}

		#toc-toggle-inline {
			vertical-align: 0.05em;
			font-size: 80%;
			color: gray;
			color: hsla(203,20%,40%,.7);
			border-style: none;
			background: transparent;
			position: relative;
		}
		#toc-toggle-inline:hover:not(:active),
		#toc-toggle-inline:focus:not(:active) {
			text-shadow: 1px 1px silver;
			top: -1px;
			left: -1px;
		}

		#toc-nav :active {
			color: #C00;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;    /* Inherit the font family. */
		line-height: 1.2;        /* Keep wrapped headings compact */
		hyphens: manual;         /* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		background: transparent;
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#subtitle {
		/* #subtitle is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	 border-left: 0.5em solid #DEF;
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	  padding: .5em;
	  border: thin solid #ddd; border-radius: .5em;
	  margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	  margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	  margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	 margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	 margin-left: -2em;
	}
	dl.switch {
	 padding-left: 2em;
	}
	dl.switch > dt {
	 text-indent: -1.5em;
	 margin-top: 1em;
	}
	dl.switch > dt + dt {
	 margin-top: 0;
	}
	dl.switch > dt::before {
	 content: '\21AA';
	 padding: 0 0.5em 0 0;
	 display: inline-block;
	 width: 1em;
	 text-align: right;
	 line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: medium;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del { color: red;  text-decoration: line-through; }
	ins { color: #080; text-decoration: underline;    }

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		page-break-inside: avoid;
		hyphens: none;
		text-transform: none;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

  /* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		text-decoration: none;
		border-bottom: 1px solid #707070;
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		border-bottom-color: #BBB;
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #C00;
		border-color: #C00;
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	/* For autogen numbers, add
	   .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,    .sidefigure img,    figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote {
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	.issue,
	.note,
	.example,
	.advisement,
	.assertion,
	blockquote {
		margin: 1em auto;
	}
	.note  > p:first-child,
	.issue > p:first-child,
	blockquote > :first-child {
		margin-top: 0;
	}
	blockquote > :last-child {
		margin-bottom: 0;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #E05252;
		background: #FBE9E9;
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		text-transform: uppercase;
		color: #AE1E1E;
		padding-right: 1em;
		text-transform: uppercase;
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	   or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #E0CB52;
		background: #FCFAEE;
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		text-transform: uppercase;
		color: #827017;
		min-width: 7.5em;
		display: block;
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	   or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52E052;
		background: #E9FBE9;
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary::before,
	details.note > summary > .marker {
		text-transform: uppercase;
		display: block;
		color: hsl(120, 70%, 30%);
	}
	/* Add .note::before { content: "Note"; } for autogen label,
	   or use class="marker" to mark up the label in source. */

	details.note > summary {
		display: block;
		color: hsl(120, 70%, 30%);
	}
	details.note[open] > summary {
		border-bottom: 1px silver solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		background: #EEE;
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-style: none solid;
		background: #FFEECC;
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement > .marker {
		color: #B35F00;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: #fdd;
		color: red;
		font-weight: bold;
		padding: .75em 1em;
		border: thick red;
		border-style: solid;
		border-radius: 1em;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 1em;
		right: 1em;
		bottom: 1em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #DEF;
		margin: 1.2em 0;
		border-left: 0.5em solid #8CCBF2;
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def           td.footnote {
		padding-top: 0.6em;
	}
	table.def           td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		 <table class="data"> highlights structural relationships in a table
		 when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		 Use class="complex data" for particularly complicated tables --
		 (This will draw more lines: busier, but clearer.)

		 Use class="long" on table cells with paragraph-like contents
		 (This will adjust text alignment accordingly.)
		 Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P1725R0<br>Modular Topic Design</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Published Proposal, <time class="dt-updated" datetime="2019-06-17">2019-06-17</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://wg21.link/p1725">https://wg21.link/p1725</a>
     <dt>Author:
     <dd>
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:cjdb.ns@gmail.com">Christopher Di Bella</a>
     <dt>Audience:
     <dd>SG20
     <dt>Project:
     <dd>ISO/IEC JTC1/SC22/WG21 14882: Programming Language — C++
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>SG20 advised that <a data-link-type="biblio" href="#biblio-p1389r0">[P1389R0]</a> should move away from a linear stage-based model into a more modular topic-based model. This proposal aims to start the discussion for evaluating the the class of modules that are suitable for curriculum guidelines.</p>
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li><a href="#motivation"><span class="secno">1</span> <span class="content">Motivation</span></a>
    <li><a href="#design-goals"><span class="secno">2</span> <span class="content">Design goals</span></a>
    <li><a href="#a-non-exhausive-list-of-modules"><span class="secno">3</span> <span class="content">A non-exhausive list of modules</span></a>
    <li><a href="#bikeshedding"><span class="secno">4</span> <span class="content">Bikeshedding</span></a>
    <li><a href="#acknowledgements"><span class="secno">5</span> <span class="content">Acknowledgements</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="motivation"><span class="secno">1. </span><span class="content">Motivation</span><a class="self-link" href="#motivation"></a></h2>
   <p>It was noted in the SG20 Kona face-to-face that learning is an iterative process, requring
malleability, and that the stages outlined in P1389 were too rigid and linear; this might be too
restrictive on curriculum design as a result. This proposal sets out to ask SG20 to discuss the
ideas behind a set of topic <a class="property" data-link-type="propdesc">modules</a> where stages are embedded into a module. The benefit of the
guidelines having sets of topics as opposed to sets of stages is that teachers will be able to
formulate their own curricula more easily.</p>
   <p>P1389R0 stated that that a student should be able to meet all of the objectives and satisfy all of
the outcomes in Stage 1 before they are ready to progress to Stage 2, and so on. This means that
there are some unrelated topics that are coupled together. In hindsight, the author of P1389 also
acknowledges that the sets of stages is closer to a prescibed curriculum than intended. For example,
some of P1389’s Stage 1 has algorithms, basic I/O, computation constructs, containers, contracts,
and designing and using classes. None of these topics are strictly related, but Stage 2 is
completely blocked until all the topics in Stage 1 are exhausted. Since P1389 advises derived types
be introduced in Stage 2 -- and Stage 2 is blocked until Stage 1 is completed -- P1389 excludes the
possibility of a curriculum introducing derived types as a part of the class design topic, despite
it has no real dependency on basic I/O.</p>
   <p>If P1389 or its successor were to advise modules of topics, where strict dependencies are outlined,
then this would make it possible for both curriculum designs in the previous paragraph to co-exist
and still conform to the recommendations outlined in the 'Standing Document for Teaching C++ to
C++ Novices with Programming Experience' (P1389’s target). This will help shape the Standing
Documents that SG20 outputs, so that they are significantly less prescriptive, and satisfy the
advisory role outlined in the SG20 charter, as opposed to accidentally becoming a prescriptive
curriculum.</p>
   <h2 class="heading settled" data-level="2" id="design-goals"><span class="secno">2. </span><span class="content">Design goals</span><a class="self-link" href="#design-goals"></a></h2>
   <p>It should be noted that while P1725 suggests a handful of modules and topics that fall within those
modules, it is by no means an exhaustive list of either. Furthermore, P1725R0 does not make any
attempt to draw a dependency graph among the topics listed in each topic. The author is requesting
the help of SG20 to formulate an exhaustive list of modules and topics, as well as a strong
dependency graph that will help teachers structure their curricula.</p>
   <p>These modules are designed to have their own assoicated objectives and outcomes. A curriculum’s
objectives are essentially a contract between a student and the course. By the end of a course, a
student should have developed certain knowledge, understanding, and skills about particular topics.
These are assessable through course outcomes, which advise that a student should be able to do
something related with that knowledge, or related to that skill. For example, Table 1 outlines a few
objectives and outcomes from a hypothetical introductory C++ course.</p>
   <p><b>Note: Table 1 is an example set of objectives and outcomes for a particular hypothetical course
and is deliberately incomplete: P1725 is <i>not</i> proposing the contents of Table 1 be added to
any document published by SG20.</b></p>
   <table>
    <tbody>
     <tr>
      <td><b>Objective</b>
      <td><b>Outcome</b>
     <tr>
      <td>Students will develop
      <td>A student
     <tr>
      <td>1. knowledge and understanding about how software engineers build systems
      <td>
       <dl>
        <dt>P1.1
        <dd> chooses the correct data structures, algorithms, libraries, and tools for engineering
        software 
        <dt>P1.2
        <dd>consults the most appropriate resources for building a system
       </dl>
     <tr>
      <td>2. knowledge and understanding about why testing is an important for software development
      <td>
       <dl>
        <dt>P2.1
        <dd>designs unit-tests to validate that the individual components of their are correct
        <dt>P2.2
        <dd> designs integration-tests to validate that their individual components work together to
        provide the correct solution 
       </dl>
     <tr>
      <td>3. knowledge and understanding about why benchmarking is important for software development
      <td>
       <dl>
        <dt>P3.1
        <dd>designs benchmarks to prove that one choice is "more efficient" than another
       </dl>
     <tr>
      <td>4. knowledge and understanding about software engineering tools
      <td>
       <dl>
        <dt>P4.1
        <dd>chooses the correct tools to help solve the problem
       </dl>
     <tr>
      <td>5. skills in the C++ programming language
      <td>
       <dl>
        <dt>P5.1
        <dd>wirtes programs that correctly sovle the problem using C++
        <dt>P5.2
        <dd>writes programs that take advantage of modern C++ programming techniques
        <dt>P5.3
        <dd>reads and understands existing C++ code to understand the current state of a solution
        <dt>P5.4
        <dd> modifies or extends existing C++ code without the need for major rewrites to well-written
        code 
       </dl>
   </table>
   <h2 class="heading settled" data-level="3" id="a-non-exhausive-list-of-modules"><span class="secno">3. </span><span class="content">A non-exhausive list of modules</span><a class="self-link" href="#a-non-exhausive-list-of-modules"></a></h2>
   <p>Table 2 outlines a non-exhaustive list of modules and their related topics. The modules are not
listed in a meaningful order; instead, they are listed so that the table is evenly formatted.</p>
   <table>
    <tbody>
     <tr>
      <td>
        <b>C++ compilation model</b> 
       <ul>
        <li>declarations
        <li>definitions
        <li>headers
        <li>modules
        <li>translation units
       </ul>
      <td>
        <b>Error handling</b> 
       <ul>
        <li>contracts
        <li>exception handling
        <li>monadic programming
       </ul>
      <td>
        <b>I/O</b> 
       <ul>
        <li>character I/O
        <li>from-string conversions
        <li>file I/O
        <li>GUIs (using a third-party library)
        <li>to-string conversions
       </ul>
     <tr>
      <td>
        <b>C++ object model</b> 
       <ul>
        <li>copy semantics
        <li>constant expressions
        <li>constant objects
        <li>constructors
        <li>conversions
        <li>destructors
        <li>free store
        <li>lambdas
        <li>move semantics
        <li>objects
        <li>pass-by-value
        <li>pass-by-reference
        <li>pointers
        <li>references
        <li>references-to-<code class="highlight"><c- k>const</c-></code>
        <li>reference semantics
        <li>resources
        <li>rule-of-five
        <li>rule-of-zero
        <li>scope
        <li>smart pointers
        <li>special member functions
        <li>types
        <li>values
        <li>value semantics
       </ul>
      <td>
        <b>Functions</b> 
       <ul>
        <li>calling functions
        <li>contracts
        <li>function templates
        <li>lambdas
        <li>member functions
        <li>overloading
        <li>parameters
        <li>pass-by-value
        <li>pass-by-reference
        <li>returning multiple values
        <li>return value optimisation
        <li>user-defined literals
        <li>virtual functions
       </ul>
      <td>
        <b>User-defined types</b> 
       <ul>
        <li>access
        <li>class templates
        <li>constructors
        <li>data members
        <li>derived types
        <li>destructors
        <li>friends
        <li>interface inhertiance
        <li>member functions
        <li><code class="highlight"><c- n>optional</c-></code> and <code class="highlight"><c- n>variant</c-></code> as sum types
        <li>rule-of-five
        <li>rule-of-zero
        <li>special member functions
        <li>static members
        <li><code class="highlight"><c- k>struct</c-></code>s and <code class="highlight"><c- k>class</c-></code>es as product types
        <li>user-defined literals
        <li>variable templates
        <li>virtual functions
       </ul>
     <tr>
      <td>
        <b>Program design</b> 
       <ul>
        <li>algorithms
        <li>concepts
        <li>containers
        <li>contracts
        <li>contributing to a pre-existing project
        <li>error handling
        <li>interface inheritance
        <li>I/O design
        <li>iterators
        <li>ranges
        <li>resource handling
       </ul>
      <td>
        <b>Type system</b> 
       <ul>
        <li>conversions
        <li>fundamental types
        <li>function overloading
        <li>scoped enumerations
        <li>template type parameters
        <li>user-defined types
       </ul>
      <td>
        <b>Tooling</b> 
       <ul>
        <li>build system
        <li>compiler
        <li>continuous integration
        <li>debugger
        <li>formatter
        <li>IDE
        <li>libraries
        <li>linter
        <li>optimiser
        <li>package manager
        <li>test tools
        <li>version control
       </ul>
     <tr>
      <td> <b>History of C++</b> <br> No topic suggestions at present. 
      <td> <b>Interop with C</b> <br> No topic suggestions at present. 
      <td> <b>Undefined behaviour</b> <br> No topic suggestions at present. 
   </table>
   <p>An astute reader should notice that there are a few topics that are mentioned in multiple modules.
This highlights that the above modules could perhaps be further refined <i>or</i> that certain
topics cannot be taught in isolation. Given that features of C++ are designed to work with one
another, the author believes that the latter case is more likely. The reader should also note that
both <a class="property" data-link-type="propdesc">types</a> and 'user-defined types' have been listed as modules <i>and</i> topics within other
modules.</p>
   <p>The author would like to propose that SG20 adopt the module/topic model -- even if it is in a
different form to what is outlined above -- and begin discussing the kinds of modules desired, the
topics underneath each module, the objectives for each module, and the relevant module outcomes
associated with each objective.</p>
   <h2 class="heading settled" data-level="4" id="bikeshedding"><span class="secno">4. </span><span class="content">Bikeshedding</span><a class="self-link" href="#bikeshedding"></a></h2>
   <p>It’s been noted that the term <a class="property" data-link-type="propdesc">module</a> is overloaded with core language. Terms such as <a class="property" data-link-type="propdesc">unit</a> may be
more applicable.</p>
   <h2 class="heading settled" data-level="5" id="acknowledgements"><span class="secno">5. </span><span class="content">Acknowledgements</span><a class="self-link" href="#acknowledgements"></a></h2>
   <p>The author would like to thank JC van Winkel for his direct feedback on this proposal, as well as
the members of SG20 who provided feedback on P1389R0’s structure.</p>
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  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
  <dl>
   <dt id="biblio-p1389r0">[P1389R0]
   <dd>Christopher Di Bella, Simon Brand, Michael Adams. <a href="https://wg21.link/p1389r0">Standing Document for SG20: Guidelines for Teaching C++ to Beginners</a>. URL: <a href="https://wg21.link/p1389r0">https://wg21.link/p1389r0</a>
  </dl>