Cisco Systems, Inc.

1899 Wynkoop St, Suite 600 Denver CO 80202 United States jhildebr@cisco.com

This document defines an HTML format that can be used for the production of Internet-Drafts and RFCs. If you are viewing a version of this document other than the HTML generated by the editor, your a missing vital information. Download a canonical version from http://cursive.net/draft-hildebrand-html-rfc-2012-07-16.html.

If you are viewing a version of this document other than the HTML generated by the editor, your a missing vital information. Download a canonical version from http://cursive.net/draft-hildebrand-html-rfc-2012-07-16.html. The RFC Series has been in existence for over 40 years. During much of that time, the limitations of character set, line and page length, and graphics restrictions of RFC documents met the most immediate needs of the majority of authors and readers. As technology changed, new formats that allowed for a richer set of edit, search and display features came in to use, and tools were created to convert the plain ASCII documents to other desired formats such as HTML, PDF, and Microsoft Word. While the converted versions of the RFCs are widely available, the canonical display format remains the plain text, ASCII, line-printer structured one. The canonical source format is nroff. Canonical source and display versions of an RFC exists for several reasons: to provide verification of the content of an RFC in case inconsistencies are created when a document is converted to another format or mirrored to another location to verify the final content of a document in cases of legal dispute to aid in the conversion of the RFC in to formats requested by the community The current basic format of RFC source and display documents have two characteristics that are considered by the RFC Series Editor to be critical to the RFC Series, including: persistence (tools to read, edit, and print the documents remain easily accessible to everyone) convertibility (the plain text version is simple to convert to other formats) That said, the very simple nature of the current display format in particular introduces a variety of limitations, the list of which has grown as changes in technology create new expectations: ASCII art is considered by some to be a major limitation in expressing visually-oriented information the internationalization of the authorship and the Internet is introducing Unicode codepoints not expressible in 7-bit ASCII the more common forms of display (web pages, smaller devices) make the limitations of page and line length a hindrance to the reading of an RFC tools for people with visual impairments may stumble over the page-oriented structure of the current format; large fonts on a screen that is not large enough to show an entire line, for example, can make the current format difficult to read, since lines do not re-wrap automatically

This memo describes a format that can be used both as the canonical input format to the RFC Series Editor (RSE), as well as an archival format. Some document authors will write documents directly in this format (perhaps with tooling to generate the more repetitive tasks), and some authors will prefer other formats as their original source, all of which MUST be able to generate the format described in this memo. This memo has the following goals: Define a strict subset of HTML appropriate for Internet-Draft and RFC Series documents Serve as a comprehensive example of all of the HTML elements that are permissible

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

One of the major goals of the HTML format is to ensure accessibility for the following consumers of documents written in the format: People with impaired vision, including those that use large fonts and those that use screen readers People with difficulty distinguishing between colors People who use devices with small screens, such as cell phones Other groups TBD Specific instances where these goals are important in the design choices of the format have been called out in the text. NOTE: designing for these consumers does not preclude the use of features they cannot use, but does require that key semantic data is not lost when read using the tools and settings that are required by a given constituency.

The format specified here is a subset of HTML, deemed to be widely-implemented by common browsers at the time that the specification was created, likely to continue to be widely-implemented in the future, and unlikely to cause security issues.

The following rules SHALL be enforced before submittal. The HTML source MUST be encoded as UTF-8, as specified in RFC3629. The HTML source MUST be formatted in the manner of well-formed XML, with all element start tags having matching end tags (or <element /> for empty elements), and all elements properly nested. HTML "boolean" attributes MUST be formatted in the attr='attr' style. Single quotes (U+0027 APOSTROPHE: ') MUST be used to quote attribute values. Unquoted attribute values MUST NOT be used. HTML SHALL be indented using spaces (not tabs). Each child element SHALL be indented two spaces more than its parent element, unless the child element is mixed with non-whitespace-only text children of the same parent element. Each logical line MUST be terminated solely with a \n (U+000A: LINE FEED), otherwise known as "Unix-style" line endings. Other than \n (U+000A: LINE FEED), code points less than " " (U+0020: SPACE) (otherwise known as "control characters") MUST NOT be used. Any character references that would generate these code points (e.g. ) MUST NOT be used. NOTE: this rule explicitly forbids \t (U+0009: CHARACTER TABULATION), \f (U+000C: FORM FEED), and \r (U+000D: CARRIAGE RETURN) from appearing in the source. Unicode codepoints that are unassigned at the time of publication MUST not be used. Any Unicode codepoint higher than ~ (U+007E: TILDE) MUST serve an explicit purpose that enhances the understanding of the document. Author names and examples are two known cases. The intent is that the document MUST be understandable by a reader with the ability to read technical English. Each text-containing element such as headings (<h1>-<h6>), paragraphs (<p>), or list items (<li>), MUST be serialized as a single line without wrapping. NOTE: none of these rules affect the rendered output of the HTML, but are intended to increase the chance that multiple tools that process the format will generate identical syntax. In turn, this will make difference tools that operate on the HTML source easier to write.

The HTML comprising the document MUST be valid according to the latest version of the HTML specification at the publishing, starting with the version commonly known as HTML5. Although the HTML specification mandates several of syntax and structure rules in this document, they are called out here for emphasis.

The DOCTYPE of the document MUST be "html", which declares that the document is compliant with HTML5. For example, the document will start with exactly this string:

<!DOCTYPE html>

The root element of the document MUST be <html>. This element SHOULD include a lang attribute, whose value is a RFC5646 language tag describing the natural language of the document. For documents submitted to the RFC Series or Internet-Draft Series, the language tag MUST be "en", meaning "English". If the lang attribute is not present, its value should be taken to be "en".

In order to be correctly processed by browsers that load the HTML using a mechanism that does not provide a valid MIME content-type or charset, the HTML <head> element MUST contain a <meta> element, with the attributes http-equiv='Content-Type' and content='text/html; charset=utf-8'. This will look like:

<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />

The <head> SHOULD contain an embedded CSS stylesheet in a <style> element. The styles in the stylesheet are to be set consistently between documents by the RFC Editor, according to the best practices of the day. The RFC Editor SHALL choose a stylesheet that does not modify the meaning of the normative text of the document. The RFC Editor SHALL make the stylesheet available via a standard protocol (e.g. HTTP or HTTPS) for ease of authorship. However, when a document is submitted, external stylesheets (other than "local.css" as specified below) are NOT ALLOWED. The stylesheet itself MUST NOT be considered as normative information. To ensure consistent formatting, individual style attributes SHOULD NOT be used in the main portion of the document source except in highly exceptional circumstances; each use MUST be individually justified. Different readers of a specification will desire different tweaks to the stylesheet. To facilitate this, the <head> SHOULD include a <link> to a stylesheet in the same directory as the HTML file, named "local.css", after the embedded stylesheet. Note that this "local.css" file will not exist for most users; browsers will correspondingly ignore this <link>. When the document is used canonically, these local style overrides MUST NOT be in effect. For example:

<head> <style type='text/css'> <!-- /* RFC-editor styles */ --> </style> <link rel='stylesheet' type='text/css' href='local.css' /> </head>

Words or phrases may be emphasized using the <strong> element for "bold", and the <em> element for "italics". Underlining MUST NOT be used except for links, to avoid visual confusion. Text-only emphasis MUST NOT be used. The RFC Editor will set a policy that reflects the current feelings of the community as to whether this emphasis markup is allowed in documents that are submitted for publication in the RFC series.

HTML comments MAY be used, but MUST NOT contain normative information. One example is to clarify particular choices in the HTML format. Example:

<!-- Automatically generated: do not modify -->

Each section of the document SHALL be formatted as a <div> tag, with a class attribute with value "section". A document-unique, id attribute SHOULD be assigned to each section <div>. The id MAY be human-readable or generated. NOTE: XML requires id attributes to be unique across an entire document: Each section <div> MUST contain a header tag (<h2>-<h6>) of the appropriate depth, with top-level sections getting an <h2> tag, and each nested section getting the next higher header level. If more than five levels of headers are required, <h6> MUST be used for each deeper-nested section. However, nesting sections more than five levels deep is NOT RECOMMENDED. The text in each header tag MUST begin with the section number. Section numbers MUST begin at "1.", and MUST increment by one for each successive section at the same level. Subsections MUST be numbered by appending the subsection number to the parent section number. It is RECOMMENDED that the section number be wrapped in an <a> element, whose href attribute points to the corresponding section div with a local relative reference. This <a> element SHOULD have the CSS class self-ref. Within a section, each "normal" paragraph MUST be surrounded by a <p> element. For example:

<div class='section' id='example'> <h2><a class='self-ref' href='#example'>1.</a> Example Section</h2> <p>This is a description of the example</p> <div class='section' id='nested'> <h3><a class='self-ref' href='#nested'>1.1.</a> Nested Section</h3> <p>This is a description of the nested section.</p> <p>This is the second description paragraph.</p> </div> </div>

Appendices are special cases of top-level sections. Each appendix of the document SHALL be formatted as a <div> tag, with a class attribute with value "appendix". A document-unique, id attribute SHOULD be assigned to each section <div>. The id MAY be human-readable or generated. Each appendix <div> MUST contain an <h2> element containing text that describes the purpose of the appendix. Appendices are identified to the reader with Latin capital letters A-Z, in order. It is NOT RECOMMENDED to have more than 26 appendices, but if required, appendices "AA.", "AB.", etc. follow Appendix Z. Inside the appendix, subsections MUST be formatted per Sections, numbered sequentially. For example, the first subsection of "Appendix A." is "Appendix A.1.". For example:

<div class='appendix' id='acknowledgements'> <h2>Appendix A. Acknowledgements</h2> <p>The author gratefully acknowledges the contributions of...</p> <div class='section' id='contributors'> <h3>Appendix A.1. Contributors</h2> <p>These people contributed text...</p> </div> </div>

Paragraphs MUST be contained in a section <div> or an appendix <div>. A document-unique, id attribute SHOULD be assigned to each <p>. The id will usually be machine-generated, but MAY be human-readable if desired. It is RECOMMENDED that each paragraph be kept relatively small compared to a "page" in previous RFC formats, so that references to each paragraph are at least as valuable as page references have been in previous formats.

Lists may be used inside a section <div>, and may nest in other lists as needed. However, lists MUST NOT be nested inside a <p> element. Unordered lists (<ul>) and ordered lists (<ol>) may both be used. For example:

<div class='section' id='lists'> <h4>Unordered list</h4> <p id='lists-p-1'>An explanation:</p> <ul> <li>One</li> <li>Two</li> <ol> <li>Two.1: (this one is numbered)</li> </ol> </ul> </div>

References to other paragraphs or sections in the same document MUST use an <a> element with an href attribute with a fragment that points at the id attribute of the target (i.e. the id prefixed with a #). The target element MUST have a human-readable id attribute, which MUST be stable even when tooling generates new id attributes. For example:

See <a href='#example'>Example Section</a> for more details

References to standards are special, in that they generate formal bibliographical metadata. All links to standards in the main body of the text MUST jump to the bibliographical entry; the href MUST be of the form #[series]:[number]. For example:

href='#RFC2119'

Valid series identifiers include: 3gpp: The 3rd Generation Partnership Project ansi: American National Standards Institute ccitt: ITU Telecommunication Standardization Sector fips: Federal Information Processing Standard id: Internet-Drafts ieee: Institute of Electrical and Electronics Engineers iso: International Organization for Standardization itu: International Telecommunication Union nist: National Institute of Standards and Technology oasis: Organization for the Advancement of Structured Information Standards pkcs: Public-Key Cryptography Standards rfc: Request For Comments w3c: The World Wide Web Consortium xep: XMPP Standards Foundation The text inside the link SHOULD be a human-readable colloquial representation of the standard name and/or number. Normative references MUST use <a> elements with class ref. Example:

See: <a class='ref' href='#RFC2119'>RFC2119</a>

Informative references MUST use <a> elements with class inforef. Example:

See: <a class='inforef' href='#RFC2119'>RFC2119</a>

References to other documents that are not standards SHOULD be linked using the http: or https: URI scheme, and MUST be linked using a a URI scheme that is widely-deployed at the time that the document is published, and which does not raise any security or stability issues. In particular, javascript: references MUST NOT be used. Links using the mailto: scheme SHOULD be limited to the author's address information. For example:

<a href='http://example.com/'>Example</a>

This section describes how to format several types of information that occur regularly in documents for the Internet-Draft and RFC Series which are not descriptive text.

The RFC2119 keywords in the document MAY be set off with special markup. If so, they MUST be surrounded with a <span> element continaing the CSS class rfc2119. For example:

If so, they <span class='rfc2119'>MUST</span> be surrounded

The author may want to inject notes to the reader that are not to be a part of the final document that is published by the RFC editor. These notes MAY use any format desired by the author that would otherwise be legal in the document, but the outermost element of the note MUST have a CSS class with value rfceditor-remove.

<div class='rfceditor-remove'> <h2>Editorial Notes</h2> <p>...</p> </div>

The table of contents for the document MUST appear in a <div> element, which SHOULD precede any of the sections of proper document content. The <div> element MUST have an id attribute with value toc. The <div> element SHOULD contain an <h2> element containing the string Table of Contents, followed by nested <ul> and <li> elements describing the structure of the document, with links to each of the sections mentioned. For example:

<div id='toc'> <h2>Table of Contents</h2> <ul> <li> <div>1. <a href='#introduction'>Introduction</a></div> <ul> <li> <div>1.1. <a href='#background'>Background</a></div> </li> ...

NOTE: the Table of Contents SHOULD NOT be considered meta-data for the document. The sections themselves SHOULD contain all of the data that is required.

Include an image using the <img> tag with a src attribute. During the editing process, it may be useful to keep the value of the src attribute as a file name relative to the document, or a http(s) URL. However, upon submission, the final version of a document SHALL include a data: URI as specified in RFC2397. The image MIME type of the image SHALL be image/png, as specified in RFC2083. The RFC Editor can allow other image types in the future, at the Editor's discretion, as the state of the art and common implementation patterns change. Consider how images will look when printed. Consider how your images will be used by vision-impaired readers, including those readers with color vision deficiency. For example, images SHOULD NOT have meaningful distinctions conveyed only by color differences, and images SHOULD be available in high enough resolution that readers with other vision deficiencies can zoom in to see detail. Images MUST NOT be animated. The alt attribute is REQUIRED, and MUST be a complete, accessible description of the image. The height and width attributes SHOULD be used to specify the size of the image in pixels. Images MUST be wrapped in a <figure> element. The <figure> element SHOULD contain a <figcaption> element after the <img> element, which SHOULD contain text that describes the image. For example:

<figure> <img src='data:image/png;base64,[BASE64-encoded PNG]' alt='A description of the diagram' width='236' height='176'/> <figcaption>Possible workflow for processing HTML RFCs</figcaption> </figure>

Images SHOULD NOT be normative. Instead, the information contained in the image SHOULD be adequately conveyed in the textual description that accompanies the image.

SVG can be included directly in the HTML source, surrounded by a <figure> element and succeeded by a <figcaption> element, as described in Section 3.3.4. The root <svg> element MUST contain a <title> or <desc> element that fully describes the diagram for accessibility to screen readers; this is similar to the alt attribute on images. For example:

<figure id='fig-2'> <svg xmlns='http://www.w3.org/2000/svg'> <title>A sample SVG</title> <desc>This is a sample image, with a title and description</desc> ... </svg> <figcaption>Sample SVG</figcaption> </figure>

Might render as: Note that there are currently more browsers that can deal with <img> elements (or their alt text) than are able to generate any sensible fallback rendering from SVG. Until this changes, authors might consider replacing their SVG with a rendered image.

Use the <code> element to set aside literal references to code or protocol elements in the middle of a paragraph. If desired, the language of the code or protocol can be declared using a class attribute starting with language-. For example:

Use the <code class='language-html'>&lt;code&gt;</code> element

Larger sections of code or protocol can be included using a <pre> element with a class attribute of code. If desired, the language of the code or protocol can be declared using a further class value starting with language- (multiple class values are separated by spaces in HTML). The text inside the <pre> element will be rendered in a monospace font, with whitespace maintained. For example:

<pre class='code language-html'> &lt;html&gt; &lt;body /&gt; &lt;/html&gt; </pre>

Will be rendered as:

<html> <body /> </html>

Depending on author style, blocks of code MAY be enclosed in a <figure> element, with a <figcaption> element that describes the block. For example, see Figure 3.

ASCII art is still preferred by some authors in preference to an image or SVG. The RFC Editor may decide to prefer images or SVG, or may decide to prohibit ASCII art in the future, depending on the needs of the community at the time of publishing. Until that time, to include ASCII art, wrap a <pre> element with class='ascii' in a <figure> along with a <figcaption>, as if the <pre> element were an image, as specified in the Section 3.3.4. For example:

<figure> <pre class='ascii'> +-----------+ | original | &lt;+ +-----------+ | | | | nit | edit v | nit (no-op) +-----------+ | +-------------- | | | | | canonical | | +-------------&gt; | | -+ +-----------+ </pre> <figcaption>Sample ASCII art</figcaption> </figure>

Packet format descriptions can be encoded as a <table> element wrapped in a <figure> along with a <figcaption>, as if the <pre> element were an image, as specified in Section 3.3.4. For consistent formatting, the <table> element should have class pdu. For example:

<figure> <figcaption>Sample packet format</figcaption> <table class='pdu'> [table describing the packet] </table> </figure>

Would be rendered as:

Metadata for the document SHOULD be easily extractable from the document by tools that ordinarily process HTML. Typically, the class and id attributes can be used to query the document using CSS-style selectors. The metadata scheme SHOULD be designed such that the element name is not required in order to select a given piece of data. Instead, any element that can contain text can be used for a given class or id to be selected. The value of the data contained by the selected element(s) consists of the concatenation of all of the text from all of the child nodes of the selected element or elements, with each run of consecutive whitespace Unicode codepoints [codepoints with the White_Space property, such as U+0020 (SPACE), U+0009 (CHARACTER TABULATION), U+000A (LINE FEED), U+000C (FORM FEED), U+000D (CARRIAGE RETURN), U+00A0 (NON-BREAKING SPACE), and U+2029 (PARAGRAPH SEPARATOR)] compressed to a single U+0020 (SPACE). The metadata scheme MUST allow unambiguous selection. The id attribute is used to identify pieces of data that are guaranteed to be unique across the document. Any element with an id attribute can also be used as a fragment target in a URI by starting with the base URI of the document, then appending "#" (U+0023: NUMBER SIGN) and the value of the id attribute. In CSS, the element with a given id attribute value is selected by prepending the value with "#" (U+0023: NUMBER SIGN). For example, the following HTML in a document with the URI http://example.com/index.html:

<div id='example'>Important Text</div>

Can be targeted directly with the URL http://example.com/index.html#example, and the CSS selector #example. The class attribute is a catch-all tagging mechanism for everything in the document that might not be unique. Multiple classes may be defined on a single element by setting the class attribute to a space-separated list of classes. All of the elements with a given class name can be selected in CSS by prepending the class name with "." (U+002E: FULL STOP).

Information about the document as a whole. The <div> element with id='document' SHOULD be the first child element of the HTML body. For example:

<div id='document'> <div class='identifiers'> <div class='workgroup'>Network Working Group</div> <div class='series'>Internet-Draft</div> <div class='status'>Standards Track</div> <div class='published'>2012-07-07</div> <div class='expires'>2013-01-07</div> <div class='version'>00</div> </div> <div class='authors'> <div class='author'> <span class='initial'>J.</span> <span class='surname'>Hildebrand</span> <span class='company'>Cisco Systems, Inc.</span> </div> </div> </div>

More details for this format will be included in future drafts of this document.

The title of the document MUST appear in an <h1> element, which SHOULD follow dirctly after the Document Information. The <h1> element MUST have an id attribute with value title. For example:

<h1 id='title'>HTML RFC Format</h1>

The abstract for the document MUST appear in a <div> element, which SHOULD follow directly after the Title. The <div> element MUST have an id attribute with value abstract. The <div> element SHOULD contain an <h2> element containing the word Abstract, and MUST contain one or more <p> elements contianing text that describes the document succintly. For example:

<div id='abstract'> <h2>Abstract</h2> <p>This document defines an HTML format...</p> </div>

The IPR boilerplate for the document MUST appear in a <div> element, which SHOULD follow directly after the Abstract. The <div> element MUST have an id attribute with value ipr and a CSS class of the name of the relevant IPR ruleset. The only valid values for the IPR ruleset class are trust200902, noModificationTrust200902, and noDerivativesTrust200902 at this time. The contents of the <div> element are to be set correctly for the given ruleset, based on guidance from the IETF trust. For example:

<div id='ipr' class='trust200902'> <h2>Status of this Memo</h2> <p>...</p> <h2>Copyright Notice</h2> <p>...</p> </div>

Question: should the valid IPR classes be put in an IANA registry along with their boilerplate expansions?

NOTE: this document currently uses the approach specified by "hCard". The author recommends that the vcarddav Working Group of the IETF be tasked to propose an approach for HTML embedding of vCard that is aligned with RFC 6350. In particular, the language and altid mechanisms of RFC 6350 are not explicitly mentioned in hCard, and are required in order to fit the desire for authors' names to be representable both by English readers as well as the native language of the author. This section will be augmented with normative text when an approach is decided upon. A quick example (as an existence proof) can be found in Figure 6. The rendered version can be found in the authors section for this document.

TBD: define microformat for bibliographical data, perhaps based on the citation work at microformats.org.

This draft itself is a good example of how to use the format. Please view-source.

#include <stdio.h> int main(int argc, char **argv) { printf("Hello, IETF\n"); return 0; }

Include an image tag with class='sequence', where the alt text is the WebSequenceDiagrams.com source for the diagram. Before publication, this approach will be replaced by something more well-specified and not requiring third-party software.

<figure> <img class='sequence' alt=' title Authentication Sequence Alice-&gt;Bob: Authentication Request note right of Bob: Bob thinks about it Bob-&gt;Alice: Authentication Response' /> <figcaption>A sample sequence diagram</figcaption> </figure>

Augmented Backus-Naur Form is a way of describing formal syntax, described in RFC5234. Include ABNF (without extra indentation) in a <pre> element, with CSS class "code" and "language-abnf". For example:

<pre class='code language-abnf'> label = top-level *4section-num top-level = section-num / appendix-let section-num = 1*DIGIT "." appendix-let = 1*CAP "." CAP = %x41-5A ; A-Z DIGIT = %x30-39 ; 0-9 </pre>

Is rendered as:

label = top-level *4section-num top-level = section-num / appendix-let section-num = 1*DIGIT "." appendix-let = 1*CAP "." CAP = %x41-5A ; A-Z DIGIT = %x30-39 ; 0-9

For now, just use an image (as specified in Section 3.3.4), with the alt text being a LaTeX formula that would produce the image. For example: Future versions of this document will likely favor SVG or MathML representations of formulae, if browser support and accessibility concerns are addressed.

Since RFCs are sometimes exchanged outside the normal Web sandboxing mechanism (e.g. rsync to a mirror) then loaded from a local file, more care must be taken with the HTML than is ordinary on the Web. In particular, the intent with the format is to forbid any embedded code such as JavaScript as well as all mechanisms that could be used to execute code outside of the browser such as plugins or non-static media (such as video).

TBD

Boutell.Com, Inc.

PO Box 20837 Seattle WA 98102 US +1 206 329 4969 boutell@boutell.com

This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits. PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store gamma and chromaticity data for improved color matching on heterogeneous platforms. This specification defines the Internet Media Type image/png. Harvard University

1350 Mass. Ave. Cambridge MA 02138 - +1 617 495 3864 sob@harvard.edu

General keyword In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. Authors who follow these guidelines should incorporate this phrase near the beginning of their document: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Note that the force of these words is modified by the requirement level of the document in which they are used. Xerox Palo Alto Research Center

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Applications URL uniform resource ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279. The IETF policies about Intellectual Property Rights (IPR), such as patent rights, relative to technologies developed in the IETF are designed to ensure that IETF working groups and participants have as much information about any IPR constraints on a technical proposal as possible. The policies are also intended to benefit the Internet community and the public at large, while respecting the legitimate rights of IPR holders. This memo details the IETF policies concerning IPR related to technology worked on within the IETF. It also describes the objectives that the policies are designed to meet. This memo updates RFC 2026 and, with RFC 3978, replaces Section 10 of RFC 2026. This memo also updates paragraph 4 of Section 3.2 of RFC 2028, for all purposes, including reference [2] in RFC 2418. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. The IETF policies about rights in Contributions to the IETF are designed to ensure that such Contributions can be made available to the IETF and Internet communities while permitting the authors to retain as many rights as possible. This memo details the IETF policies on rights in Contributions to the IETF. It also describes the objectives that the policies are designed to meet. This memo obsoletes RFCs 3978 and 4748 and, with BCP 79 and RFC 5377, replaces Section 10 of RFC 2026. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document describes the structure, content, construction, and semantics of language tags for use in cases where it is desirable to indicate the language used in an information object. It also describes how to register values for use in language tags and the creation of user-defined extensions for private interchange. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. The Unicode Consortium Internet technical specifications often need to define a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. The current specification documents ABNF. It balances compactness and simplicity with reasonable representational power. The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges. This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. [STANDARDS-TRACK] This document defines the vCard data format for representing and exchanging a variety of information about individuals and other entities (e.g., formatted and structured name and delivery addresses, email address, multiple telephone numbers, photograph, logo, audio clips, etc.). This document obsoletes RFCs 2425, 2426, and 4770, and updates RFC 2739. [STANDARDS-TRACK]

This section collects all of the elements that are allowed in the HTML RFC format. Each element is listed with a set of allowed attributes, and a list of the parent elements in which the element may be placed. The attributes class, id, and lang are allowed on all elements. All other elements, attributes, and nesting approaches MUST NOT be used. Element Attributes Parents a href, title address, div, figcaption, h2, h3, h4, h5, li, p, span, td address div blockquote div body html br td, th code li, p, td div address, body, div, li em p figcaption figure figure div h1 body h2 div h3 div h4 div h5 div head html html img alt, height, src, width figure li ol, ul link href, rel, type head meta content, http-equiv, name head ol div p blockquote, div, td pre div, figure span address, div, li, p, span strong p, pre svg height, viewbox, width figure table div, figure tbody table td colspan tr th colspan tr thead table title head tr tbody, thead ul div, li, td

Although the author can add class information to any element, the following class names have special meaning in an HTML RFC: Class Meaning adr appendix ascii author authors code company country-name date edge email expires family-name figref fn formula given-name graph hidden identifiers initial language-abnf language-c language-html locality n nickname node note org pdu postal-code published ref reflinks region rfc2119 rfceditor-remove section sectref self-ref sequence series series-info status street-address surname title toc trust200902 vcard version workgroup

Although the author can add an id attribute to any element, the following id values SHOULD NOT be used except for the role defined for each below: ID Meaning document Data about the document, including dates, name, version, etc. title The title of the document, usually applied to a <h1> element. abstract The abstract for the document, usually applied to a <div> element that contains a heading and paragraphs of text. ipr The Intellectual Property Rights associated with the document. The class attribute of the same element will contain a machine-readable IPR statement name from this list: trust200902: This is appropriate for most drafts, where the entire content of the draft is written by the draft's authors, or all authors of other material have given explicit permission to use their work. noModificationTrust200902: This is appropriate for drafts where the authors wish to place the additional condition that if the draft is published as an RFC, it must have no changes other than formatting. An example might be a document published by another organization that permits copying but not modification. noDerivativesTrust200902: This is appropriate for drafts not intended to be published as RFCs. pre5378Trust200902: This is appropriate for drafts that include material submitted to the IETF prior to RFC 5378 (10 Nov 2008), where the authors of that material have not given explicit permission to use their work in this draft. An example might be a draft using material from an RFC whose author has died or cannot be located, or who thinks your draft is stupid. The element with this id will contain all of the IPR and status boilerplate text Note: an IANA registry may be required for this attribute in the future. venue The venue for discussion. Inside the element tagged with this id will be one or more <a> elements that describe the discussion venue for Internet-Drafts. toc The Table of Contents references The section containing bibliographical data, including sections for normative and informative references. normative The section containing normative document references. informative The section containing informative document references. authors The section containing data about the authors of the document. security The section containing the Security Considerations for the document. iana The section containing the IANA Considerations for the document. acknowledgments The section containing the author's acknowledgments.

The author gratefully acknowledges the contributions of: Heather Flanagan and Patrick Linskey