File: rfc8820.html

package info (click to toggle)
doc-rfc 20230121-1
links: PTS, VCS
area: non-free
in suites: bookworm, forky, sid, trixie
size: 1,609,944 kB
file content (1650 lines) | stat: -rw-r--r-- 62,222 bytes
parent folder | download | duplicates (2)
<!DOCTYPE html>
<html lang="en" class="RFC BCP">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 8820: URI Design and Ownership</title>
<meta content="Mark Nottingham" name="author">
<meta content="
       Section 1.1.1 of RFC 3986 defines URI syntax as &quot;a federated and
      extensible naming system wherein each scheme's specification may further
      restrict the syntax and semantics of identifiers using that scheme.&quot;  In
      other words, the structure of a URI is defined by its scheme. While it
      is common for schemes to further delegate their substructure to the
      URI's owner, publishing independent standards that mandate particular
      forms of substructure in URIs is often problematic. 
       This document provides guidance on the specification of URI
      substructure in standards. 
       This document obsoletes RFC 7320 and updates RFC 3986. 
    " name="description">
<meta content="xml2rfc 2.46.0" name="generator">
<meta content="URI structure" name="keyword">
<meta content="8820" name="rfc.number">
<link href="rfc8820.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

  NOTE: Changes at the bottom of this file overrides some earlier settings.

  Once the style has stabilized and has been adopted as an official RFC style,
  this can be consolidated so that style settings occur only in one place, but
  for now the contents of this file consists first of the initial CSS work as
  provided to the RFC Formatter (xml2rfc) work, followed by itemized and
  commented changes found necssary during the development of the v3
  formatters.

*/

/* fonts */
@import url('https://fonts.googleapis.com/css?family=Noto+Sans'); /* Sans-serif */
@import url('https://fonts.googleapis.com/css?family=Noto+Serif'); /* Serif (print) */
@import url('https://fonts.googleapis.com/css?family=Roboto+Mono'); /* Monospace */

@viewport {
  zoom: 1.0;
  width: extend-to-zoom;
}
@-ms-viewport {
  width: extend-to-zoom;
  zoom: 1.0;
}
/* general and mobile first */
html {
}
body {
  max-width: 90%;
  margin: 1.5em auto;
  color: #222;
  background-color: #fff;
  font-size: 14px;
  font-family: 'Noto Sans', Arial, Helvetica, sans-serif;
  line-height: 1.6;
  scroll-behavior: smooth;
}
.ears {
  display: none;
}

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
  margin: 1em 0 0.5em;
  font-weight: bold;
  line-height: 1.3;
}
#title {
  clear: both;
  border-bottom: 1px solid #ddd;
  margin: 0 0 0.5em 0;
  padding: 1em 0 0.5em;
}
.author {
  padding-bottom: 4px;
}
h1 {
  font-size: 26px;
  margin: 1em 0;
}
h2 {
  font-size: 22px;
  margin-top: -20px;  /* provide offset for in-page anchors */
  padding-top: 33px;
}
h3 {
  font-size: 18px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h4 {
  font-size: 16px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h5, h6 {
  font-size: 14px;
}
#n-copyright-notice {
  border-bottom: 1px solid #ddd;
  padding-bottom: 1em;
  margin-bottom: 1em;
}
/* general structure */
p {
  padding: 0;
  margin: 0 0 1em 0;
  text-align: left;
}
div, span {
  position: relative;
}
div {
  margin: 0;
}
.alignRight.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
  padding: 0;
}
.alignRight {
  margin: 1em 0;
}
.alignRight > *:first-child {
  border: none;
  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
  clear: both;
  display: block;
  border: none;
}
svg {
  display: block;
}
.alignCenter.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignCenter.art-text pre {
  padding: 0;
}
.alignCenter {
  margin: 1em 0;
}
.alignCenter > *:first-child {
  border: none;
  /* this isn't optimal, but it's an existence proof.  PrinceXML doesn't
     support flexbox yet.
  */
  display: table;
  margin: 0 auto;
}

/* lists */
ol, ul {
  padding: 0;
  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
  margin-left: 1em;
}
li {
  margin: 0 0 0.25em 0;
}
.ulCompact li {
  margin: 0;
}
ul.empty, .ulEmpty {
  list-style-type: none;
}
ul.empty li, .ulEmpty li {
  margin-top: 0.5em;
}
ul.compact, .ulCompact,
ol.compact, .olCompact {
  line-height: 100%;
  margin: 0 0 0 2em;
}

/* definition lists */
dl {
}
dl > dt {
  float: left;
  margin-right: 1em;
}
/* 
dl.nohang > dt {
  float: none;
}
*/
dl > dd {
  margin-bottom: .8em;
  min-height: 1.3em;
}
dl.compact > dd, .dlCompact > dd {
  margin-bottom: 0em;
}
dl > dd > dl {
  margin-top: 0.5em;
  margin-bottom: 0em;
}

/* links */
a {
  text-decoration: none;
}
a[href] {
  color: #22e; /* Arlen: WCAG 2019 */
}
a[href]:hover {
  background-color: #f2f2f2;
}
figcaption a[href],
a[href].selfRef {
  color: #222;
}
/* XXX probably not this:
a.selfRef:hover {
  background-color: transparent;
  cursor: default;
} */

/* Figures */
tt, code, pre, code {
  background-color: #f9f9f9;
  font-family: 'Roboto Mono', monospace;
}
pre {
  border: 1px solid #eee;
  margin: 0;
  padding: 1em;
}
img {
  max-width: 100%;
}
figure {
  margin: 0;
}
figure blockquote {
  margin: 0.8em 0.4em 0.4em;
}
figcaption {
  font-style: italic;
  margin: 0 0 1em 0;
}
@media screen {
  pre {
    overflow-x: auto;
    max-width: 100%;
    max-width: calc(100% - 22px);
  }
}

/* aside, blockquote */
aside, blockquote {
  margin-left: 0;
  padding: 1.2em 2em;
}
blockquote {
  background-color: #f9f9f9;
  color: #111; /* Arlen: WCAG 2019 */
  border: 1px solid #ddd;
  border-radius: 3px;
  margin: 1em 0;
}
cite {
  display: block;
  text-align: right;
  font-style: italic;
}

/* tables */
table {
  width: 100%;
  margin: 0 0 1em;
  border-collapse: collapse;
  border: 1px solid #eee;
}
th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.5em 0.75em;
}
th {
  text-align: left;
  background-color: #e9e9e9;
}
tr:nth-child(2n+1) > td {
  background-color: #f5f5f5;
}
table caption {
  font-style: italic;
  margin: 0;
  padding: 0;
  text-align: left;
}
table p {
  /* XXX to avoid bottom margin on table row signifiers. If paragraphs should
     be allowed within tables more generally, it would be far better to select on a class. */
  margin: 0;
}

/* pilcrow */
a.pilcrow {
  color: #666; /* Arlen: AHDJ 2019 */
  text-decoration: none;
  visibility: hidden;
  user-select: none;
  -ms-user-select: none;
  -o-user-select:none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}
@media screen {
  aside:hover > a.pilcrow,
  p:hover > a.pilcrow,
  blockquote:hover > a.pilcrow,
  div:hover > a.pilcrow,
  li:hover > a.pilcrow,
  pre:hover > a.pilcrow {
    visibility: visible;
  }
  a.pilcrow:hover {
    background-color: transparent;
  }
}

/* misc */
hr {
  border: 0;
  border-top: 1px solid #eee;
}
.bcp14 {
  font-variant: small-caps;
}

.role {
  font-variant: all-small-caps;
}

/* info block */
#identifiers {
  margin: 0;
  font-size: 0.9em;
}
#identifiers dt {
  width: 3em;
  clear: left;
}
#identifiers dd {
  float: left;
  margin-bottom: 0;
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

/* The prepared/rendered info at the very bottom of the page */
.docInfo {
  color: #666; /* Arlen: WCAG 2019 */
  font-size: 0.9em;
  font-style: italic;
  margin-top: 2em;
}
.docInfo .prepared {
  float: left;
}
.docInfo .prepared {
  float: right;
}

/* table of contents */
#toc  {
  padding: 0.75em 0 2em 0;
  margin-bottom: 1em;
}
nav.toc ul {
  margin: 0 0.5em 0 0;
  padding: 0;
  list-style: none;
}
nav.toc li {
  line-height: 1.3em;
  margin: 0.75em 0;
  padding-left: 1.2em;
  text-indent: -1.2em;
}
/* references */
.references dt {
  text-align: right;
  font-weight: bold;
  min-width: 7em;
}
.references dd {
  margin-left: 8em;
  overflow: auto;
}

.refInstance {
  margin-bottom: 1.25em;
}

.references .ascii {
  margin-bottom: 0.25em;
}

/* index */
.index ul {
  margin: 0 0 0 1em;
  padding: 0;
  list-style: none;
}
.index ul ul {
  margin: 0;
}
.index li {
  margin: 0;
  text-indent: -2em;
  padding-left: 2em;
  padding-bottom: 5px;
}
.indexIndex {
  margin: 0.5em 0 1em;
}
.index a {
  font-weight: 700;
}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
  .index ul {
    -moz-column-count: 2;
    -moz-column-gap: 20px;
  }
  .index ul ul {
    -moz-column-count: 1;
    -moz-column-gap: 0;
  }
}

/* authors */
address.vcard {
  font-style: normal;
  margin: 1em 0;
}

address.vcard .nameRole {
  font-weight: 700;
  margin-left: 0;
}
address.vcard .label {
  font-family: "Noto Sans",Arial,Helvetica,sans-serif;
  margin: 0.5em 0;
}
address.vcard .type {
  display: none;
}
.alternative-contact {
  margin: 1.5em 0 1em;
}
hr.addr {
  border-top: 1px dashed;
  margin: 0;
  color: #ddd;
  max-width: calc(100% - 16px);
}

/* temporary notes */
.rfcEditorRemove::before {
  position: absolute;
  top: 0.2em;
  right: 0.2em;
  padding: 0.2em;
  content: "The RFC Editor will remove this note";
  color: #9e2a00; /* Arlen: WCAG 2019 */
  background-color: #ffd; /* Arlen: WCAG 2019 */
}
.rfcEditorRemove {
  position: relative;
  padding-top: 1.8em;
  background-color: #ffd; /* Arlen: WCAG 2019 */
  border-radius: 3px;
}
.cref {
  background-color: #ffd; /* Arlen: WCAG 2019 */
  padding: 2px 4px;
}
.crefSource {
  font-style: italic;
}
/* alternative layout for smaller screens */
@media screen and (max-width: 1023px) {
  body {
    padding-top: 2em;
  }
  #title {
    padding: 1em 0;
  }
  h1 {
    font-size: 24px;
  }
  h2 {
    font-size: 20px;
    margin-top: -18px;  /* provide offset for in-page anchors */
    padding-top: 38px;
  }
  #identifiers dd {
    max-width: 60%;
  }
  #toc {
    position: fixed;
    z-index: 2;
    top: 0;
    right: 0;
    padding: 0;
    margin: 0;
    background-color: inherit;
    border-bottom: 1px solid #ccc;
  }
  #toc h2 {
    margin: -1px 0 0 0;
    padding: 4px 0 4px 6px;
    padding-right: 1em;
    min-width: 190px;
    font-size: 1.1em;
    text-align: right;
    background-color: #444;
    color: white;
    cursor: pointer;
  }
  #toc h2::before { /* css hamburger */
    float: right;
    position: relative;
    width: 1em;
    height: 1px;
    left: -164px;
    margin: 6px 0 0 0;
    background: white none repeat scroll 0 0;
    box-shadow: 0 4px 0 0 white, 0 8px 0 0 white;
    content: "";
  }
  #toc nav {
    display: none;
    padding: 0.5em 1em 1em;
    overflow: auto;
    height: calc(100vh - 48px);
    border-left: 1px solid #ddd;
  }
}

/* alternative layout for wide screens */
@media screen and (min-width: 1024px) {
  body {
    max-width: 724px;
    margin: 42px auto;
    padding-left: 1.5em;
    padding-right: 29em;
  }
  #toc {
    position: fixed;
    top: 42px;
    right: 42px;
    width: 25%;
    margin: 0;
    padding: 0 1em;
    z-index: 1;
  }
  #toc h2 {
    border-top: none;
    border-bottom: 1px solid #ddd;
    font-size: 1em;
    font-weight: normal;
    margin: 0;
    padding: 0.25em 1em 1em 0;
  }
  #toc nav {
    display: block;
    height: calc(90vh - 84px);
    bottom: 0;
    padding: 0.5em 0 0;
    overflow: auto;
  }
  img { /* future proofing */
    max-width: 100%;
    height: auto;
  }
}

/* pagination */
@media print {
  body {

    width: 100%;
  }
  p {
    orphans: 3;
    widows: 3;
  }
  #n-copyright-notice {
    border-bottom: none;
  }
  #toc, #n-introduction {
    page-break-before: always;
  }
  #toc {
    border-top: none;
    padding-top: 0;
  }
  figure, pre {
    page-break-inside: avoid;
  }
  figure {
    overflow: scroll;
  }
  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }
  h2+*, h3+*, h4+*, h5+*, h6+* {
    page-break-before: avoid;
  }
  pre {
    white-space: pre-wrap;
    word-wrap: break-word;
    font-size: 10pt;
  }
  table {
    border: 1px solid #ddd;
  }
  td {
    border-top: 1px solid #ddd;
  }
}

/* This is commented out here, as the string-set: doesn't
   pass W3C validation currently */
/*
.ears thead .left {
  string-set: ears-top-left content();
}

.ears thead .center {
  string-set: ears-top-center content();
}

.ears thead .right {
  string-set: ears-top-right content();
}

.ears tfoot .left {
  string-set: ears-bottom-left content();
}

.ears tfoot .center {
  string-set: ears-bottom-center content();
}

.ears tfoot .right {
  string-set: ears-bottom-right content();
}
*/

@page :first {
  padding-top: 0;
  @top-left {
    content: normal;
    border: none;
  }
  @top-center {
    content: normal;
    border: none;
  }
  @top-right {
    content: normal;
    border: none;
  }
}

@page {
  size: A4;
  margin-bottom: 45mm;
  padding-top: 20px;
  /* The follwing is commented out here, but set appropriately by in code, as
     the content depends on the document */
  /*
  @top-left {
    content: 'Internet-Draft';
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-left {
    content: string(ears-top-left);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-center {
    content: string(ears-top-center);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-right {
    content: string(ears-top-right);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @bottom-left {
    content: string(ears-bottom-left);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-center {
    content: string(ears-bottom-center);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-right {
      content: '[Page ' counter(page) ']';
      vertical-align: top;
      border-top: solid 1px #ccc;
  }
  */

}

/* Changes introduced to fix issues found during implementation */
/* Make sure links are clickable even if overlapped by following H* */
a {
  z-index: 2;
}
/* Separate body from document info even without intervening H1 */
section {
  clear: both;
}


/* Top align author divs, to avoid names without organization dropping level with org names */
.author {
  vertical-align: top;
}

/* Leave room in document info to show Internet-Draft on one line */
#identifiers dt {
  width: 8em;
}

/* Don't waste quite as much whitespace between label and value in doc info */
#identifiers dd {
  margin-left: 1em;
}

/* Give floating toc a background color (needed when it's a div inside section */
#toc {
  background-color: white;
}

/* Make the collapsed ToC header render white on gray also when it's a link */
@media screen and (max-width: 1023px) {
  #toc h2 a,
  #toc h2 a:link,
  #toc h2 a:focus,
  #toc h2 a:hover,
  #toc a.toplink,
  #toc a.toplink:hover {
    color: white;
    background-color: #444;
    text-decoration: none;
  }
}

/* Give the bottom of the ToC some whitespace */
@media screen and (min-width: 1024px) {
  #toc {
    padding: 0 0 1em 1em;
  }
}

/* Style section numbers with more space between number and title */
.section-number {
  padding-right: 0.5em;
}

/* prevent monospace from becoming overly large */
tt, code, pre, code {
  font-size: 95%;
}

/* Fix the height/width aspect for ascii art*/
pre.sourcecode,
.art-text pre {
  line-height: 1.12;
}


/* Add styling for a link in the ToC that points to the top of the document */
a.toplink {
  float: right;
  margin-right: 0.5em;
}

/* Fix the dl styling to match the RFC 7992 attributes */
dl > dt,
dl.dlParallel > dt {
  float: left;
  margin-right: 1em;
}
dl.dlNewline > dt {
  float: none;
}

/* Provide styling for table cell text alignment */
table td.text-left,
table th.text-left {
  text-align: left;
}
table td.text-center,
table th.text-center {
  text-align: center;
}
table td.text-right,
table th.text-right {
  text-align: right;
}

/* Make the alternative author contact informatio look less like just another
   author, and group it closer with the primary author contact information */
.alternative-contact {
  margin: 0.5em 0 0.25em 0;
}
address .non-ascii {
  margin: 0 0 0 2em;
}

/* With it being possible to set tables with alignment
  left, center, and right, { width: 100%; } does not make sense */
table {
  width: auto;
}

/* Avoid reference text that sits in a block with very wide left margin,
   because of a long floating dt label.*/
.references dd {
  overflow: visible;
}

/* Control caption placement */
caption {
  caption-side: bottom;
}

/* Limit the width of the author address vcard, so names in right-to-left
   script don't end up on the other side of the page. */

address.vcard {
  max-width: 30em;
  margin-right: auto;
}

/* For address alignment dependent on LTR or RTL scripts */
address div.left {
  text-align: left;
}
address div.right {
  text-align: right;
}

/* Provide table alignment support.  We can't use the alignX classes above
   since they do unwanted things with caption and other styling. */
table.right {
 margin-left: auto;
 margin-right: 0;
}
table.center {
 margin-left: auto;
 margin-right: auto;
}
table.left {
 margin-left: 0;
 margin-right: auto;
}

/* Give the table caption label the same styling as the figcaption */
caption a[href] {
  color: #222;
}

@media print {
  .toplink {
    display: none;
  }

  /* avoid overwriting the top border line with the ToC header */
  #toc {
    padding-top: 1px;
  }

  /* Avoid page breaks inside dl and author address entries */
  .vcard {
    page-break-inside: avoid;
  }

}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
}
div#internal-metadata {
  padding: 0.5em;                       /* to match the external-metadata padding */
}
/* Styling for title RFC Number */
h1#rfcnum {
  clear: both;
  margin: 0 0 -1em;
  padding: 1em 0 0 0;
}
/* Make .olPercent look the same as <ol><li> */
dl.olPercent > dd {
  margin-bottom: 0.25em;
  min-height: initial;
}
/* Give aside some styling to set it apart */
aside {
  border-left: 1px solid #ddd;
  margin: 1em 0 1em 2em;
  padding: 0.2em 2em;
}
aside > dl,
aside > ol,
aside > ul,
aside > table,
aside > p {
  margin-bottom: 0.5em;
}
/* Additional page break settings */
@media print {
  figcaption, table caption {
    page-break-before: avoid;
  }
}
/* Font size adjustments for print */
@media print {
  body  { font-size: 10pt;      line-height: normal; max-width: 96%; }
  h1    { font-size: 1.72em;    padding-top: 1.5em; } /* 1*1.2*1.2*1.2 */
  h2    { font-size: 1.44em;    padding-top: 1.5em; } /* 1*1.2*1.2 */
  h3    { font-size: 1.2em;     padding-top: 1.5em; } /* 1*1.2 */
  h4    { font-size: 1em;       padding-top: 1.5em; }
  h5, h6 { font-size: 1em;      margin: initial; padding: 0.5em 0 0.3em; }
}
/* Sourcecode margin in print, when there's no pilcrow */
@media print {
  .artwork,
  .sourcecode {
    margin-bottom: 1em;
  }
}
/* Avoid narrow tables forcing too narrow table captions, which may render badly */
table {
  min-width: 20em;
}
/* ol type a */
ol.type-a { list-style-type: lower-alpha; }
ol.type-A { list-style-type: upper-alpha; }
ol.type-i { list-style-type: lower-roman; }
ol.type-I { list-style-type: lower-roman; }
/* Apply the print table and row borders in general, on request from the RPC,
and increase the contrast between border and odd row background sligthtly */
table {
  border: 1px solid #ddd;
}
td {
  border-top: 1px solid #ddd;
}
tr:nth-child(2n+1) > td {
  background-color: #f8f8f8;
}
/* Use style rules to govern display of the TOC. */
@media screen and (max-width: 1023px) {
  #toc nav { display: none; }
  #toc.active nav { display: block; }
}
/* Add support for keepWithNext */
.keepWithNext {
  break-after: avoid-page;
  break-after: avoid-page;
}
/* Add support for keepWithPrevious */
.keepWithPrevious {
  break-before: avoid-page;
}
/* Change the approach to avoiding breaks inside artwork etc. */
figure, pre, table, .artwork, .sourcecode  {
  break-before: avoid-page;
  break-after: auto;
}
/* Avoid breaks between <dt> and <dd> */
dl {
  break-before: auto;
  break-inside: auto;
}
dt {
  break-before: auto;
  break-after: avoid-page;
}
dd {
  break-before: avoid-page;
  break-after: auto;
  orphans: 3;
  widows: 3
}
span.break, dd.break {
  margin-bottom: 0;
  min-height: 0;
  break-before: auto;
  break-inside: auto;
  break-after: auto;
}
/* Undo break-before ToC */
@media print {
  #toc {
    break-before: auto;
  }
}
/* Text in compact lists should not get extra bottim margin space,
   since that would makes the list not compact */
ul.compact p, .ulCompact p,
ol.compact p, .olCompact p {
 margin: 0;
}
/* But the list as a whole needs the extra space at the end */
section ul.compact,
section .ulCompact,
section ol.compact,
section .olCompact {
  margin-bottom: 1em;                    /* same as p not within ul.compact etc. */
}
/* The tt and code background above interferes with for instance table cell
   backgrounds.  Changed to something a bit more selective. */
tt, code {
  background-color: transparent;
}
p tt, p code {
  background-color: #f9f9f9;
}
</style>
<link href="rfc-local.css" rel="stylesheet" type="text/css">
<link href="https://dx.doi.org/10.17487/rfc8820" rel="alternate">
  <link href="urn:issn:2070-1721" rel="alternate">
  <link href="https://datatracker.ietf.org/doc/draft-nottingham-rfc7320bis-03" rel="prev">
  </head>
<body>
<script src="https://www.rfc-editor.org/js/metadata.min.js"></script>
<table class="ears">
<thead><tr>
<td class="left">RFC 8820</td>
<td class="center">URI Design and Ownership</td>
<td class="right">June 2020</td>
</tr></thead>
<tfoot><tr>
<td class="left">Nottingham</td>
<td class="center">Best Current Practice</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc8820" class="eref">8820</a></dd>
<dt class="label-bcp">BCP:</dt>
<dd class="bcp">190</dd>
<dt class="label-obsoletes">Obsoletes:</dt>
<dd class="obsoletes">
<a href="https://www.rfc-editor.org/rfc/rfc7320" class="eref">7320</a> </dd>
<dt class="label-updates">Updates:</dt>
<dd class="updates">
<a href="https://www.rfc-editor.org/rfc/rfc3986" class="eref">3986</a> </dd>
<dt class="label-category">Category:</dt>
<dd class="category">Best Current Practice</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2020-06" class="published">June 2020</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Author:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">M. Nottingham</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8820</h1>
<h1 id="title">URI Design and Ownership</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">Section 1.1.1 of RFC 3986 defines URI syntax as "a federated and
      extensible naming system wherein each scheme's specification may further
      restrict the syntax and semantics of identifiers using that scheme."  In
      other words, the structure of a URI is defined by its scheme. While it
      is common for schemes to further delegate their substructure to the
      URI's owner, publishing independent standards that mandate particular
      forms of substructure in URIs is often problematic.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
<p id="section-abstract-2">This document provides guidance on the specification of URI
      substructure in standards.<a href="#section-abstract-2" class="pilcrow">¶</a></p>
<p id="section-abstract-3">This document obsoletes RFC 7320 and updates RFC 3986.<a href="#section-abstract-3" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This memo documents an Internet Best Current Practice.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further information
            on BCPs is available in Section 2 of RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc8820">https://www.rfc-editor.org/info/rfc8820</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2020 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.1.2.1">
                <p id="section-toc.1-1.1.2.1.1" class="keepWithNext"><a href="#section-1.1" class="xref">1.1</a>.  <a href="#name-intended-audience" class="xref">Intended Audience</a><a href="#section-toc.1-1.1.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.1.2.2">
                <p id="section-toc.1-1.1.2.2.1" class="keepWithNext"><a href="#section-1.2" class="xref">1.2</a>.  <a href="#name-notational-conventions" class="xref">Notational Conventions</a><a href="#section-toc.1-1.1.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-best-current-practices-for-" class="xref">Best Current Practices for Standardizing Structured URIs</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.2.2.1">
                <p id="section-toc.1-1.2.2.1.1"><a href="#section-2.1" class="xref">2.1</a>.  <a href="#name-uri-schemes" class="xref">URI Schemes</a><a href="#section-toc.1-1.2.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.2">
                <p id="section-toc.1-1.2.2.2.1"><a href="#section-2.2" class="xref">2.2</a>.  <a href="#name-uri-authorities" class="xref">URI Authorities</a><a href="#section-toc.1-1.2.2.2.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.3">
                <p id="section-toc.1-1.2.2.3.1"><a href="#section-2.3" class="xref">2.3</a>.  <a href="#name-uri-paths" class="xref">URI Paths</a><a href="#section-toc.1-1.2.2.3.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.4">
                <p id="section-toc.1-1.2.2.4.1"><a href="#section-2.4" class="xref">2.4</a>.  <a href="#name-uri-queries" class="xref">URI Queries</a><a href="#section-toc.1-1.2.2.4.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.5">
                <p id="section-toc.1-1.2.2.5.1"><a href="#section-2.5" class="xref">2.5</a>.  <a href="#name-uri-fragment-identifiers" class="xref">URI Fragment Identifiers</a><a href="#section-toc.1-1.2.2.5.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-alternatives-to-specifying-" class="xref">Alternatives to Specifying Structure in URIs</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.6.2.1">
                <p id="section-toc.1-1.6.2.1.1"><a href="#section-6.1" class="xref">6.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.6.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.2">
                <p id="section-toc.1-1.6.2.2.1"><a href="#section-6.2" class="xref">6.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.6.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-appendix.a" class="xref">Appendix A</a>.  <a href="#name-changes-from-rfc-7320" class="xref">Changes from RFC 7320</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-appendix.c" class="xref"></a><a href="#name-authors-address" class="xref">Author's Address</a><a href="#section-toc.1-1.9.1" class="pilcrow">¶</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<div id="intro">
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">URIs <span>[<a href="#RFC3986" class="xref">RFC3986</a>]</span> very often include
      structured application data. This might include artifacts from
      filesystems (often occurring in the path component) and user information
      (often in the query component). In some cases, there can even be
      application-specific data in the authority component (e.g., some
      applications are spread across several hostnames to enable a form of
      partitioning or dispatch).<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">Implementations can impose further constraints upon the structure of
      URIs; for example, many web servers use the filename extension of the
      last path segment to determine the media type of the response. Likewise,
      prepackaged applications often have highly structured URIs that can only
      be changed in limited ways (often, just the hostname and port on which
      they are deployed).<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">Because the owner of the URI (as defined in <span>[<a href="#webarch" class="xref">webarch</a>]</span>, Section 2.2.2.1) is choosing to use the
server or the application, this can be seen as reasonable delegation of authority. However, when
such conventions are mandated by a party other than the owner, it can have several potentially
detrimental effects:<a href="#section-1-3" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1-4.1">Collisions - As more ad hoc conventions for URI structure become standardized, it becomes more
likely that there will be collisions between them (especially considering that servers,
applications, and individual deployments will have their own conventions).<a href="#section-1-4.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-4.2">Dilution - When the information added to a URI is ephemeral, this dilutes its utility by reducing
its stability (see <span>[<a href="#webarch" class="xref">webarch</a>]</span>, Section 3.5.1) and can cause several alternate forms of the URI
to exist (see <span>[<a href="#webarch" class="xref">webarch</a>]</span>, Section 2.3.1).<a href="#section-1-4.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-4.3">Rigidity - Fixed URI syntax often interferes with desired deployment patterns. For example, if an
authority wishes to offer several applications on a single hostname, it becomes difficult to
impossible to do if their URIs do not allow the required flexibility.<a href="#section-1-4.3" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-4.4">Operational Difficulty - Supporting some URI conventions can be difficult in some
implementations. For example, specifying that a particular query parameter be used with "http"
URIs can preclude the use of web servers that serve the response from a filesystem. Likewise, an
application that fixes a base path for its operation (e.g., "/v1") makes it impossible to deploy
other applications with the same prefix on the same host.<a href="#section-1-4.4" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-4.5">Client Assumptions - When conventions are standardized, some clients will inevitably assume that
the standards are in use when those conventions are seen. This can lead to interoperability
problems; for example, if a specification documents that the "sig" URI query parameter indicates
that its payload is a cryptographic signature for the URI, it can lead to undesirable behavior.<a href="#section-1-4.5" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-1-5">Publishing a standard that constrains an existing URI structure in ways that aren't explicitly
allowed by <span>[<a href="#RFC3986" class="xref">RFC3986</a>]</span> (usually, by updating the URI scheme definition) is therefore sometimes
problematic, both for these reasons and because the structure of a URI needs to be firmly under
the control of its owner.<a href="#section-1-5" class="pilcrow">¶</a></p>
<p id="section-1-6">This document explains some best current practices for establishing URI structures, conventions, and
formats in standards. It also offers strategies for specifications in <a href="#alternatives" class="xref">Section 3</a>.<a href="#section-1-6" class="pilcrow">¶</a></p>
<div id="intended-audience">
<section id="section-1.1">
        <h3 id="name-intended-audience">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-intended-audience" class="section-name selfRef">Intended Audience</a>
        </h3>
<p id="section-1.1-1">This document's guidelines and requirements target the authors of specifications that constrain the
syntax or structure of URIs or parts of them. Two classes of such specifications are called out
specifically:<a href="#section-1.1-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1.1-2.1">Protocol Extensions ("Extensions") - specifications that offer new capabilities that could apply
to any identifier or to a large subset of possible identifiers, e.g., a new signature mechanism
for "http" URIs, metadata for any URI, or a new format.<a href="#section-1.1-2.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-1.1-2.2">Applications Using URIs ("Applications") - specifications that
          use URIs to meet specific needs, 
e.g., an HTTP interface to particular information on a host.<a href="#section-1.1-2.2" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-1.1-3">Requirements that target the generic class "Specifications" apply to all specifications, including
both those enumerated above and others.<a href="#section-1.1-3" class="pilcrow">¶</a></p>
<p id="section-1.1-4">Note that this specification ought not be interpreted as preventing the allocation of control of
URIs by parties that legitimately own them or have delegated that ownership; for example, a
specification might legitimately define the semantics of a URI on IANA's web site as part of
the establishment of a registry.<a href="#section-1.1-4" class="pilcrow">¶</a></p>
<p id="section-1.1-5">There may be existing IETF specifications that already deviate from the guidance in this document.
In these cases, it is up to the relevant communities (i.e., those of the URI
scheme as well as any relevant community that 
produced the specification in question) to determine an appropriate outcome, e.g., updating
the scheme definition or changing the specification.<a href="#section-1.1-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="notational-conventions">
<section id="section-1.2">
        <h3 id="name-notational-conventions">
<a href="#section-1.2" class="section-number selfRef">1.2. </a><a href="#name-notational-conventions" class="section-name selfRef">Notational Conventions</a>
        </h3>
<p id="section-1.2-1">The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>",
       "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>",
       "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>",
       "<span class="bcp14">SHOULD NOT</span>",
       "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
       "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document
       are to be interpreted as described in BCP 14
       <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> when, and only
       when, they appear in all capitals, as shown here.<a href="#section-1.2-1" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="best-current-practices-for-standardizing-structured-uris">
<section id="section-2">
      <h2 id="name-best-current-practices-for-">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-best-current-practices-for-" class="section-name selfRef">Best Current Practices for Standardizing Structured URIs</a>
      </h2>
<p id="section-2-1">This section updates <span>[<a href="#RFC3986" class="xref">RFC3986</a>]</span> by advising Specifications how they should define structure and
semantics within URIs. Best practices differ, depending on the URI component in question, as
described below.<a href="#section-2-1" class="pilcrow">¶</a></p>
<div id="uri-schemes">
<section id="section-2.1">
        <h3 id="name-uri-schemes">
<a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-uri-schemes" class="section-name selfRef">URI Schemes</a>
        </h3>
<p id="section-2.1-1">Applications and Extensions can require the use of one or more specific URI schemes; for example, it is perfectly
acceptable to require that an Application support "http" and "https" URIs. However, Applications
ought not preclude the use of other URI schemes in the future, unless they are clearly only usable
with the nominated schemes.<a href="#section-2.1-1" class="pilcrow">¶</a></p>
<p id="section-2.1-2">A Specification that defines substructure for URI schemes overall (e.g., a prefix or suffix for URI
scheme names) <span class="bcp14">MUST</span> do so by modifying <span>[<a href="#BCP35" class="xref">BCP35</a>]</span> (an exceptional circumstance).<a href="#section-2.1-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="uri-authorities">
<section id="section-2.2">
        <h3 id="name-uri-authorities">
<a href="#section-2.2" class="section-number selfRef">2.2. </a><a href="#name-uri-authorities" class="section-name selfRef">URI Authorities</a>
        </h3>
<p id="section-2.2-1">Scheme definitions define the presence, format, and semantics of an
        authority component in URIs; all other Specifications <span class="bcp14">MUST NOT</span> constrain or define the structure or the semantics for URI
        authorities, unless they update the scheme registration itself or the
        structures it relies upon (e.g., DNS name syntax, as defined in <span><a href="https://www.rfc-editor.org/rfc/rfc1034#section-3.5" class="relref">Section 3.5</a> of [<a href="#RFC1034" class="xref">RFC1034</a>]</span>).<a href="#section-2.2-1" class="pilcrow">¶</a></p>
<p id="section-2.2-2">For example, an Extension or Application cannot say that the "foo" prefix in
"https://foo_app.example.com" is meaningful or triggers special handling in
URIs, unless they update either the "http" URI scheme or the DNS hostname
syntax.<a href="#section-2.2-2" class="pilcrow">¶</a></p>
<p id="section-2.2-3">Applications can nominate or constrain the port they use, when applicable. For example,
BarApp could run over port nnnn (provided that it is properly registered).<a href="#section-2.2-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="uri-paths">
<section id="section-2.3">
        <h3 id="name-uri-paths">
<a href="#section-2.3" class="section-number selfRef">2.3. </a><a href="#name-uri-paths" class="section-name selfRef">URI Paths</a>
        </h3>
<p id="section-2.3-1">Scheme definitions define the presence, format, and semantics of a path component in URIs, although these are often delegated to the Application(s) in a given deployment.<a href="#section-2.3-1" class="pilcrow">¶</a></p>
<p id="section-2.3-2">To avoid collisions, rigidity, and erroneous client assumptions, Specifications <span class="bcp14">MUST NOT</span> define a
fixed prefix for their URI paths -- for example, "/myapp" -- unless allowed by the scheme definition.<a href="#section-2.3-2" class="pilcrow">¶</a></p>
<p id="section-2.3-3">One such exception to this requirement is registered "well-known" URIs, as specified by
<span>[<a href="#RFC8615" class="xref">RFC8615</a>]</span>. See that document for a description of the applicability of that mechanism.<a href="#section-2.3-3" class="pilcrow">¶</a></p>
<p id="section-2.3-4">Note that this does not apply to Applications defining a structure
        of a URI's path "under" a resource
controlled by the server. Because the prefix is under control of the party deploying the
Application, collisions and rigidity are avoided, and the risk of erroneous client assumptions is
reduced.<a href="#section-2.3-4" class="pilcrow">¶</a></p>
<p id="section-2.3-5">For example, an Application might define "app_root" as a deployment-controlled URI prefix.
Application-defined resources might then be assumed to be present at "{app_root}/foo" and
"{app_root}/bar".<a href="#section-2.3-5" class="pilcrow">¶</a></p>
<p id="section-2.3-6">Extensions <span class="bcp14">MUST NOT</span> define a structure within individual URI components (e.g., a prefix or suffix),
again to avoid collisions and erroneous client assumptions.<a href="#section-2.3-6" class="pilcrow">¶</a></p>
</section>
</div>
<div id="uri-queries">
<section id="section-2.4">
        <h3 id="name-uri-queries">
<a href="#section-2.4" class="section-number selfRef">2.4. </a><a href="#name-uri-queries" class="section-name selfRef">URI Queries</a>
        </h3>
<p id="section-2.4-1">The presence, format, and semantics of the query component of URIs are dependent upon many factors
and can be constrained by a scheme definition. Often, they are determined by the implementation of
a resource itself.<a href="#section-2.4-1" class="pilcrow">¶</a></p>
<p id="section-2.4-2">Applications can specify the syntax of queries for the resources under their control. However,
doing so can cause operational difficulties for deployments that do not support a particular form
of a query. For example, a site may wish to support an Application using "static" files that do not
support query parameters.<a href="#section-2.4-2" class="pilcrow">¶</a></p>
<p id="section-2.4-3">Extensions <span class="bcp14">MUST NOT</span> constrain the format or semantics of queries, to avoid collisions and erroneous
client assumptions. For example, an Extension that indicates that all query parameters with the
name "sig" indicate a cryptographic signature would collide with potentially preexisting query
parameters on sites and lead clients to assume that any matching query parameter is a signature.<a href="#section-2.4-3" class="pilcrow">¶</a></p>
<p id="section-2.4-4">Per the "Form submission" section of <span>[<a href="#HTML5" class="xref">HTML5</a>]</span>, HTML constrains the syntax of
 query strings used in form submission.
New form languages are encouraged to allow creation of a broader variety of URIs
(e.g., by allowing the form to create new path components, and so forth).<a href="#section-2.4-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="uri-fragment-identifiers">
<section id="section-2.5">
        <h3 id="name-uri-fragment-identifiers">
<a href="#section-2.5" class="section-number selfRef">2.5. </a><a href="#name-uri-fragment-identifiers" class="section-name selfRef">URI Fragment Identifiers</a>
        </h3>
<p id="section-2.5-1"><span><a href="https://www.rfc-editor.org/rfc/rfc3986#section-3.5" class="relref">Section 3.5</a> of [<a href="#RFC3986" class="xref">RFC3986</a>]</span> specifies fragment identifiers' syntax and semantics as being dependent
upon the media type of a potentially retrieved resource. As a result, other Specifications <span class="bcp14">MUST NOT</span>
define structure within the fragment identifier, unless they are explicitly defining one for reuse
by media types in their definitions (for example, as JSON Pointer <span>[<a href="#RFC6901" class="xref">RFC6901</a>]</span> does).<a href="#section-2.5-1" class="pilcrow">¶</a></p>
<p id="section-2.5-2">An Application that defines common fragment identifiers across media types not
controlled by it would engender interoperability problems with handlers for those media types
(because the new, non-standard syntax is not expected).<a href="#section-2.5-2" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="alternatives">
<section id="section-3">
      <h2 id="name-alternatives-to-specifying-">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-alternatives-to-specifying-" class="section-name selfRef">Alternatives to Specifying Structure in URIs</a>
      </h2>
<p id="section-3-1">Given the issues described in <a href="#intro" class="xref">Section 1</a>, the most successful strategy for Applications and
Extensions that wish to use URIs is to use them in the fashion for which they were designed: as links that
are exchanged as part of the protocol, rather than statically specified syntax. Several existing
specifications can aid in this.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2"><span>[<a href="#RFC8288" class="xref">RFC8288</a>]</span> specifies relation types for web links. By providing a framework for linking on the
Web, where every link has a relation type, context, and target, it allows Applications to define a
link's semantics and connectivity.<a href="#section-3-2" class="pilcrow">¶</a></p>
<p id="section-3-3"><span>[<a href="#RFC6570" class="xref">RFC6570</a>]</span> provides a standard syntax for URI Templates that can be used to dynamically insert
Application-specific variables into a URI to enable such Applications while avoiding impinging upon
URI owners' control of them.<a href="#section-3-3" class="pilcrow">¶</a></p>
<p id="section-3-4"><span>[<a href="#RFC8615" class="xref">RFC8615</a>]</span> allows specific paths to be "reserved" for standard use on URI schemes that opt into
that mechanism ("http" and "https" by default). Note, however, that this is not a general "escape
valve" for Applications that need structured URIs; see that specification for more information.<a href="#section-3-4" class="pilcrow">¶</a></p>
<p id="section-3-5">Specifying more elaborate structures in an attempt to avoid collisions is not an acceptable
solution and does not address the issues described in <a href="#intro" class="xref">Section 1</a>. For example, prefixing query parameters
with "myapp_" does not help, because the prefix itself is subject to the risk of collision (since
it is not "reserved").<a href="#section-3-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="security-considerations">
<section id="section-4">
      <h2 id="name-security-considerations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-4-1">This document does not introduce new protocol artifacts with security considerations. It prohibits
some practices that might lead to vulnerabilities; for example, if a security-sensitive mechanism
is introduced by assuming that a URI path component or query string has a particular meaning, false
positives might be encountered (due to sites that already use the chosen string). See also
<span>[<a href="#RFC6943" class="xref">RFC6943</a>]</span>.<a href="#section-4-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="iana-considerations">
<section id="section-5">
      <h2 id="name-iana-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-5-1">This document has no IANA actions.<a href="#section-5-1" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-6">
      <h2 id="name-references">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-6.1">
        <h3 id="name-normative-references">
<a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3986">[RFC3986]</dt>
        <dd>
<span class="refAuthor">Berners-Lee, T.</span><span class="refAuthor">, Fielding, R.</span><span class="refAuthor">, and L. Masinter</span>, <span class="refTitle">"Uniform Resource Identifier (URI): Generic Syntax"</span>, <span class="seriesInfo">STD 66</span>, <span class="seriesInfo">RFC 3986</span>, <span class="seriesInfo">DOI 10.17487/RFC3986</span>, <time datetime="2005-01" class="refDate">January 2005</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3986">https://www.rfc-editor.org/info/rfc3986</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8174">[RFC8174]</dt>
        <dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="webarch">[webarch]</dt>
      <dd>
<span class="refAuthor">Jacobs, I.</span><span class="refAuthor"> and N. Walsh</span>, <span class="refTitle">"Architecture of the World Wide Web, Volume One"</span>, <time datetime="2004-12" class="refDate">December 2004</time>, <span>&lt;<a href="https://www.w3.org/TR/2004/REC-webarch-20041215">https://www.w3.org/TR/2004/REC-webarch-20041215</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-6.2">
        <h3 id="name-informative-references">
<a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="BCP35">[BCP35]</dt>
        <dd>
<span class="refAuthor">Thaler, D., Ed.</span><span class="refAuthor">, Hansen, T.</span><span class="refAuthor">, and T. Hardie</span>, <span class="refTitle">"Guidelines and Registration Procedures for New URI Schemes"</span>, <span class="seriesInfo">BCP 35</span>, <span class="seriesInfo">RFC 7595</span>, <time datetime="2015-06" class="refDate">June 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/bcp35">https://www.rfc-editor.org/info/bcp35</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="HTML5">[HTML5]</dt>
        <dd>
<span class="refAuthor">WHATWG</span>, <span class="refTitle">"HTML - Living Standard"</span>, <span class="refContent">Section 4.10.21</span>, <time datetime="2020-06" class="refDate">June 2020</time>, <span>&lt;<a href="https://html.spec.whatwg.org/#form-submission">https://html.spec.whatwg.org/#form-submission</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC1034">[RFC1034]</dt>
        <dd>
<span class="refAuthor">Mockapetris, P.</span>, <span class="refTitle">"Domain names - concepts and facilities"</span>, <span class="seriesInfo">STD 13</span>, <span class="seriesInfo">RFC 1034</span>, <span class="seriesInfo">DOI 10.17487/RFC1034</span>, <time datetime="1987-11" class="refDate">November 1987</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1034">https://www.rfc-editor.org/info/rfc1034</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6570">[RFC6570]</dt>
        <dd>
<span class="refAuthor">Gregorio, J.</span><span class="refAuthor">, Fielding, R.</span><span class="refAuthor">, Hadley, M.</span><span class="refAuthor">, Nottingham, M.</span><span class="refAuthor">, and D. Orchard</span>, <span class="refTitle">"URI Template"</span>, <span class="seriesInfo">RFC 6570</span>, <span class="seriesInfo">DOI 10.17487/RFC6570</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6570">https://www.rfc-editor.org/info/rfc6570</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6901">[RFC6901]</dt>
        <dd>
<span class="refAuthor">Bryan, P., Ed.</span><span class="refAuthor">, Zyp, K.</span><span class="refAuthor">, and M. Nottingham, Ed.</span>, <span class="refTitle">"JavaScript Object Notation (JSON) Pointer"</span>, <span class="seriesInfo">RFC 6901</span>, <span class="seriesInfo">DOI 10.17487/RFC6901</span>, <time datetime="2013-04" class="refDate">April 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6901">https://www.rfc-editor.org/info/rfc6901</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6943">[RFC6943]</dt>
        <dd>
<span class="refAuthor">Thaler, D., Ed.</span>, <span class="refTitle">"Issues in Identifier Comparison for Security Purposes"</span>, <span class="seriesInfo">RFC 6943</span>, <span class="seriesInfo">DOI 10.17487/RFC6943</span>, <time datetime="2013-05" class="refDate">May 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6943">https://www.rfc-editor.org/info/rfc6943</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8288">[RFC8288]</dt>
        <dd>
<span class="refAuthor">Nottingham, M.</span>, <span class="refTitle">"Web Linking"</span>, <span class="seriesInfo">RFC 8288</span>, <span class="seriesInfo">DOI 10.17487/RFC8288</span>, <time datetime="2017-10" class="refDate">October 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8288">https://www.rfc-editor.org/info/rfc8288</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8615">[RFC8615]</dt>
      <dd>
<span class="refAuthor">Nottingham, M.</span>, <span class="refTitle">"Well-Known Uniform Resource Identifiers (URIs)"</span>, <span class="seriesInfo">RFC 8615</span>, <span class="seriesInfo">DOI 10.17487/RFC8615</span>, <time datetime="2019-05" class="refDate">May 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8615">https://www.rfc-editor.org/info/rfc8615</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="changes-from-rfc7320">
<section id="section-appendix.a">
      <h2 id="name-changes-from-rfc-7320">
<a href="#section-appendix.a" class="section-number selfRef">Appendix A. </a><a href="#name-changes-from-rfc-7320" class="section-name selfRef">Changes from RFC 7320</a>
      </h2>
<p id="section-appendix.a-1">Many of the requirements of RFC 7320 were removed, in the spirit of making this BCP guidance rather than rules.<a href="#section-appendix.a-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="acknowledgments">
<section id="section-appendix.b">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<p id="section-appendix.b-1">Thanks to <span class="contact-name">David Booth</span>, <span class="contact-name">Dave       Crocker</span>, <span class="contact-name">Tim Bray</span>, <span class="contact-name">Anne van       Kesteren</span>, <span class="contact-name">Martin Thomson</span>, <span class="contact-name">Erik Wilde</span>, <span class="contact-name">Dave Thaler</span>, and <span class="contact-name">Barry Leiba</span> for their suggestions and feedback.<a href="#section-appendix.b-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authors-addresses">
<section id="section-appendix.c">
      <h2 id="name-authors-address">
<a href="#name-authors-address" class="section-name selfRef">Author's Address</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Mark Nottingham</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:mnot@mnot.net" class="email">mnot@mnot.net</a>
</div>
<div class="url">
<span>URI:</span>
<a href="https://www.mnot.net/" class="url">https://www.mnot.net/</a>
</div>
</address>
</section>
</div>
<script>const toc = document.getElementById("toc");
toc.querySelector("h2").addEventListener("click", e => {
  toc.classList.toggle("active");
});
toc.querySelector("nav").addEventListener("click", e => {
  toc.classList.remove("active");
});
</script>
</body>
</html>