HTML Working Group T. Berners-Lee INTERNET-DRAFT MIT/W3C <draft-ietf-html-spec-03.txt> D. Connolly Expires: In six months May 31, 1995 Hypertext Markup Language - 2.0 CONTENTS 1. Introduction 2. HTML as an Application of SGML 3. HTML as an Internet Media Type 4. Document Structure 5. Character, Words, and Paragraphs 6. Hyperlinks 7. Forms 8. HTML Public Text 9. Glossary 10. Bibliography 11. Appendices 12. Acknowledgments Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the 1id-abstracts.txt listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this document is unlimited. Please send comments to the HTML working group (HTML-WG) of the Internet Engineering Task Force (IETF) at <html-wg@oclc.org>. Discussions of the group are archived at <URL:http://www.acl.lanl.gov/HTML_WG/archives.html>. In this draft, the first three sections are considered essentially finished. Sections 4 and 5 have been significantly revised and are open to comments, though I'm fairly happy with those parts. Section 6 is somewhat new: it collects all information about hyperlinking into one place. Sections 7 (forms elements) has also been revised, and there are a few points I'm not sure on. The glossary (section 8) has also been tweaked. Section 8 ``public text'' has been stable for some time, but as it's critical, I'd appreciate a careful review just the same. ABSTRACT The Hypertext Markup Language (HTML) is a simple markup language used to create hypertext documents that are platform independent. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of domains. HTML markup can represent hypertext news, mail, documentation, and hypermedia; menus of options; database query results; simple structured documents with in-lined graphics; and hypertext views of existing bodies of information. HTML has been in use by the World Wide Web (WWW) global information initiative since 1990. This specification roughly corresponds to the capabilities of HTML in common use prior to June 1994. HTML is an application of ISO Standard 8879:1986 Information Processing Text and Office Systems; Standard Generalized Markup Language (SGML). The `"text/html; version=2.0"' Internet Media Type (RFC 1590) and MIME Content Type (RFC 1521) is defined by this specification. 1. Introduction The HyperText Markup Language (HTML) is a simple data format used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of domains. 1.1. Scope HTML has been in use by the World-Wide Web (WWW) global information initiative since 1990. This specification corresponds to the capabilities of HTML in common use prior to June 1994 and referred to as ``HTML 2.0''. HTML is an application of ISO Standard 8879:1986 _Information Processing Text and Office Systems; Standard Generalized Markup Language_ (SGML). The HTML Document Type Definition (DTD) is a formal definition of the HTML syntax in terms of SGML. This specification also defines HTML as an Internet Media Type[IMEDIA] and MIME Content Type[MIME] called `text/html', or `text/html; version=2.0'. As such, it defines the semantics of the HTML syntax and how that syntax should be interpreted by user agents. 1.2. Conformance This specification governs the syntax of HTML documents and the behaviour of HTML user agents. 1.2.1. Documents A document is a conforming HTML document only if: * It is a conforming SGML document, and it conforms to the HTML DTD (see 8.1, "HTML DTD"). NOTE - There are a number of syntactic idioms that are not supported or are supported inconsistently in some historical user agent implementations. These idioms are called out in notes like this throughout this specification. HTML documents should not contain these idioms, at least until such time as support for them is widely deployed. * It conforms to the application conventions in this specification. For example, the value of the HREF attribute of the <A> element must conform to the URI syntax. * Its document character set includes ANSI/ISO 8859-1 and agrees with ISO/IEC 10646-1; that is, each code position listed in 11.1, "The ANSI/ISO 8859-1 Coded Character Set" is included, and each code position in the document character set is mapped to the same character as ISO10646 designates for that code position. NOTE - The document character set is somewhat independent of the character encoding scheme used to represent a document. For example, the ISO-2022-JP character encoding scheme can be used for HTML documents, since its repertoire is a subset of the ISO10646 repertoire. The critical distinction is that numeric character references agree with ISO10646 regardless of how the document is encoded. The HTML DTD defines a standard HTML document type and several variations, based on feature test entities: HTML.Recommended Certain features of the language are necessary for compatibility with widespread usage, but they may compromise the structural integrity of a document. This feature test entity enables a more prescriptive document type definition that eliminates those features. For example, in order to preserve the structure of a document, an editing user agent may translate HTML documents to the recommended subset, or it may require that the documents be in the recommended subset for import. HTML.Deprecated Certain features of the language are necessary for compatibility with earlier versions of the specification, but they tend to be used and implemented inconsistently, and their use is deprecated. This feature test entity enables a document type definition that eliminates these features. Documents generated by tranlation software or editing software should not contain these idioms. 1.2.2. User Agents An HTML user agent conforms to this specification if: * It parses the characters of an HTML document into data characters and markup according to [SGML]. NOTE - In the interest of robustness and extensibility, there are a number of widely deployed conventions for handling non-conforming documents. See 3.2.1, "Undeclared Markup Error Handling" for details. * It supports the `ISO-8859-1' character encoding scheme and processes each character in the ISO Latin Alphabet No. 1 as specified in 5.1, "The ISO Latin 1 Character Repertoire". NOTE - To support non-western writing systems, HTML user agents should support ISO-10646-UCS-2 or similar character encoding schemes and as much of the character repertoire of ISO10646 as is practical. * It behaves identically for documents whose parsed token sequences are identical. For example, comments and the whitespace in tags disappear during tokenization, and hence they do not influence the behaviour of conforming user agents. * It allows the user to traverse (or at least attempt to traverse, resources permitting) all hyperlinks in an HTML document. * It allows the user to express all form field values specified in an HTML document and to (attempt to) submit the values as requests to information services. 2. HTML as an Application of SGML HTML is an application of ISO 8879:1986 -- Standard Generalized Markup Language (SGML). SGML is a system for defining structured document types and markup languages to represent instances of those document types[SGML]. The public text -- DTD and SGML declaration -- of the HTML document type definition are provided in 8, "HTML Public Text". The term _HTML_ refers to both the document type defined here and the markup language for representing instances of this document type. 2.1. SGML Documents An HTML document is an SGML document; that is, a sequence of characters organized physically into a set of entities, and logically as a hierarchy of elements. The first production of the SGML grammar separates an SGML document into three parts: an SGML declaration, a prologue, and an instance. For the purposes of this specification, the prologue is a DTD. This DTD describes another grammar: the start symbol is given in the doctype declaration, the terminals are data characters and tags, and the productions are determined by the element declarations. The instance must conform to the DTD, that is, it must be in the language defined by this grammar. The SGML declaration determines the lexicon of the grammar. It specifies the document character set, which determines a character repertoire that contains all characters that occur in all text entities in the document, and the code positions associated with those characters. The SGML declaration also specifies the syntax-reference character set of the document, and a few other parameters that bind the abstract syntax of SGML to a concrete syntax. This concrete syntax determines how the sequence of characters of the document is mapped to a sequence of terminals in the grammar of the prologue. For example, consider the following document: <!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN"> <title>Parsing Example</title> <p>Some text. <em>*wow*</em></p> An HTML user agent should use the SGML declaration that is given in 8.2, "SGML Declaration for HTML". According to its document character set, `*' refers to an asterisk character. The instance above is regarded as the following sequence of terminals: 1. TITLE start-tag 2. data characters: ``Parsing Example'' 3. TITLE end-tag 4. P start-tag 5. data characters ``Some text. '' 6. EM start-tag 7. ``*wow*'' 8. EM end-tag 9. P end-tag The start symbol of the DTD grammar is HTML, and the productions are given in the public text identified by `-//IETF//DTD HTML 2.0//EN' (8.1, "HTML DTD"). Hence the terminals above parse as: HTML | \-HEAD | | | \-TITLE | | | \-<TITLE> | | | \-"Parsing Example" | | | \-</TITLE> | \-BODY | \-P | \-<P> | \-"Some text. " | \-EM | | | \-<EM> | | | \-"*wow*" | | | \-</EM> | \-</P> 2.2. HTML Lexical Syntax SGML specifies an abstract syntax and a reference concrete syntax. Aside from certain quantities and capacities (e.g. the limit on the length of a name), all HTML documents use the reference concrete syntax. In particular, all markup characters are in the repertoire of ISO 646 IRV. Data characters are drawn from the document character set (see 5, "Character, Words, and Paragraphs"). A complete discussion of SGML parsing, e.g. the mapping of a sequence of characters to a sequence of tags and data, is left to the SGML standard[SGML]. This section is only a summary. 2.2.1. Data Characters Any sequence of characters that do not constitute markup (see 9.6 ``Delimiter Recognition'' of [SGML]) are mapped directly to strings of data characters. Some markup also maps to data character strings. Numeric character references also map to single-character strings, via the document character set. Each reference to one of the general entities defined in the HTML DTD also maps to a single-character string. For example, abc<def => "abc","<","def" abc<def => "abc","<","def" Note that the terminating semicolon is only necessary when the character following the reference would otherwise be recognized as markup: abc < def => "abc ","<"," def" abc < def => "abc ","<"," def" And note that an ampersand is only recognized as markup when it is followed by a letter or digit: abc & lt def => "abc & lt def" abc & 60 def => "abc & 60 def" A useful technique for translating plain text to HTML is to replace each '<', '&', and '>' by an entity reference or numeric character reference as follows: ENTITY NUMERIC CHARACTER REFERENCE CHAR REF CHARACTER DESCRIPTION & & & Ampersand < < < Less than > > > Greater than NOTE - There are SGML mechanisms, CDATA and RCDATA, to allow most `<', `>', and `&' characters to be entered without the use of entity references. Because these features tend to be used and implemented inconsistently, and because they conflict with techniques for reducing HTML to 7 bit ASCII for transport, they are not used in this version of the HTML DTD. 2.2.2. Tags Tags delimit elements such as headings, paragraphs, lists, character highlighting, and links. Most HTML elements are identified in a document as a start-tag, which gives the element name and attributes, followed by the content, followed by the end tag. Start-tags are delimited by `<' and `>'; end tags are delimited by `</' and `>'. An example is: <H1>This is a Heading</H1> Some elements only have a start-tag without an end-tag. For example, to create a line break, you use the `<BR>' tag. Additionally, the end tags of some other elements, such as Paragraph (`</P>'), List Item (`</LI>'), Definition Term (`</DT>'), and Definition Description (`<DD>') elements, may be omitted. The content of an element is a sequence of data character strings and nested elements. Some elements, such as anchors, cannot be nested. Anchors and character highlighting may be put inside other constructs. See the HTML DTD, 8.1, "HTML DTD" for full details. NOTE - The SGML declaration for HTML specifies SHORTTAG YES, which means that there are other valid syntaxes for tags, such as NET tags, `<EM/.../'; empty start tags, `<>'; and empty end-tags, `</>'. Until support for these idioms is widely deployed, their use is strongly discouraged. 2.2.3. Names A name consists of a letter followed by up to 71 letters, digits, periods, or hyphens. Element names are not case sensitive, but entity names are. For example, `<BLOCKQUOTE>', `<BlockQuote>', and `<blockquote>' are equivalent, whereas `&' is different from `&'. In a start-tag, the element name must immediately follow the tag open delimiter `<'. 2.2.4. Attributes In a start-tag, white space and attributes are allowed between the element name and the closing delimiter. An attribute typically consists of an attribute name, an equal sign, and a value, though some attributes may be just a value. White space is allowed around the equal sign. The value of the attribute may be either: * A string literal, delimited by single quotes or double quotes and not containing any occurrences of the delimiting character. NOTE - Some historical implementations consider any occurrence of the `>' character to signal the end of a tag. For compatibility with such implementations, when `>' appears in an attribute value, it should be represented with a numeric character reference. For example, `<IMG SRC="eq1.jpg" alt="a>b">' should be written `<IMG SRC="eq1.jpg" alt="a>b">' or `<IMG SRC="eq1.jpg" alt="a>b">'. * A name token (a sequence of letters, digits, periods, or hyphens). NOTE - Some historical implementations allow any character except space or `>' in a name token. In this example, <img> is the element name, src is the attribute name, and `http://host/dir/file.gif' is the attribute value: <img src='http://host/dir/file.gif'> A useful technique for computing an attribute value literal for a given string is to replace each quote and space character by an entity reference or numeric character reference as follows: ENTITY NUMERIC CHARACTER REFERENCE CHAR REF CHARACTER DESCRIPTION TAB 	 Tab LF Line Feed CR Carriage Return   Space " " " Quotation mark & & & Ampersand For example: <IMG SRC="image.jpg" alt="First "real" example"> Note that the SGML declaration in section 13.3 limits the length of an attribute value to 1024 characters. Attributes such as ISMAP and COMPACT may be written using a minimized syntax. The markup: <UL COMPACT="compact"> can be written using a minimized syntax: <UL COMPACT> NOTE - Some historical implementations only understand the minimized syntax. 2.2.5. Comments To include comments in an HTML document, use a comment declaration. A comment declaration consists of `<!' followed by zero or more comments followed by `>'. Each comment starts with `--' and includes all text up to and including the next occurrence of `--'. In a comment declaration, white space is allowed after each comment, but not before the first comment. The entire comment declaration is ignored. NOTE - Some historical HTML implementations incorrectly consider any `>' character to be the termination of a comment. For example: <HEAD> <TITLE>HTML Comment Example</TITLE> <!-- Id: html-sgml.sgm,v 1.5 1995年05月26日 21:29:50 connolly Exp --> <!-- another -- -- comment --> <!> </HEAD> <BODY> <p> <!- not a comment, just regular old data characters -> 2.2.6. Example HTML Document <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> <HTML> <!-- Here's a good place to put a comment. --> <HEAD> <TITLE>Structural Example</TITLE> </HEAD><BODY> <H1>First Header</H1> <P>This is a paragraph in the example HTML file. Keep in mind that the title does not appear in the document text, but that the header (defined by H1) does.</P> <OL> <LI>First item in an ordered list. <LI>Second item in an ordered list. <UL COMPACT> <LI> Note that lists can be nested; <LI> Whitespace may be used to assist in reading the HTML source. </UL> <LI>Third item in an ordered list. </OL> <P>This is an additional paragraph. Technically, end tags are not required for paragraphs, although they are allowed. You can include character highlighting in a paragraph. <EM>This sentence of the paragraph is emphasized.</EM> Note that the </P> end tag has been omitted. <P> <IMG SRC ="triangle.xbm" alt="Warning: "> Be sure to read these <b>bold instructions</b>. </BODY></HTML> 3. HTML as an Internet Media Type An HTML user agent allows users to interact with resources which have HTML representations. At a minimum, it must allow users to examine and navigate the content of HTML level 1 documents. HTML user agents should be able to preserve all formatting distinctions represented in an HTML document, and be able to simultaneously present resources referred to by IMG elements (they may ignore some formatting distinctions or IMG resources at the request of the user). Conforming HTML user agents should support form entry and submission. 3.1. text/html media type This specification defines the Internet Media Type[IMEDIA] (formerly referred to as the Content Type[MIME]) called `text/html'. The following is to be registered with [IANA]. Media Type name text Media subtype name html Required parameters none Optional parameters level, charset Encoding considerations any encoding is allowed Security considerations see 3.3, "Security Considerations" The optional parameters are defined as follows: Level The level parameter specifies the feature set used in the document. The level is an integer number, implying that any features of same or lower level may be present in the document. Level 1 is all features defined in this specification except those that require the <FORM> element. Level 2 includes form processing. Level 2 is the default. Charset The charset parameter (as defined in section 7.1.1 of RFC 1521[MIME]) may be given to specify the character encoding scheme used to represent the HTML document as a sequence of octets. The default value is outside the scope of this specification; but for example, the default is `US-ASCII' in the context of MIME mail, and `ISO-8859-1' in the context of HTTP. 3.2. HTML Document Representation A message entity with a content type of `text/html' represents an HTML document, consisting of a single text entity. The `charset' parameter (whether implicit or explicit) identifies a character encoding scheme. The text entity consists of the characters determined by this character encoding scheme and the octets of the body of the message entity. 3.2.1. Undeclared Markup Error Handling To facilitate experimentation and interoperability between implementations of various versions of HTML, the installed base of HTML user agents supports a superset of the HTML 2.0 language by reducing it to HTML 2.0: markup in the form of a start-tag or end-tag whose generic identifier is not declared is mapped to nothing during tokenization. Undeclared attributes are treated similarly. The entire attribute specification of an unknown attribute (i.e., the unknown attribute and its value, if any) should be ignored. On the other hand, references to undeclared entities should be treated as data characters. For example: <div class=chapter><h1>foo</h1><p>...</div> => <H1>,"foo",</H1>,<P>,"..." xxx <P ID=z23> yyy => "xxx ",<P>," yyy Let α and β be finite sets. => "Let α and β be finite sets." Support for notifying the user of such errors is encouraged. Information providers are warned that this convention is not binding: unspecified behavior may result, as such markup is not conforming to this specification. 3.2.2. Conventional Representation of Newlines SGML specifies that a text entity is a sequence of records, each beginning with a record start character and ending with a record end character (code positions 10 and 13 respectively) (section 7.6.1, ``Record Boundaries'' in [SGML]). [MIME] specifies that a body of type `text/*' is a sequence of lines, each terminated by CRLF, that is, octets 10, 13. In practice, HTML documents are frequently represented and transmitted using an end of line convention that depends on the conventions of the source of the document; frequently, that representation consists of CR only, LF only, or a CR LF sequence. Hence the decoding of the octets will often result in a text entity with some missing record start and record end characters. Since there is no ambiguity, HTML user agents are encouraged to infer the missing record start and end characters. An HTML user agent should treat end of line in any of its variations as a word space in all contexts except preformatted text. Within preformatted text, an HTML user agent should treat any of the three common representations of end-of-line as starting a new line. 3.3. Security Considerations Anchors, embedded images, and all other elements which contain URIs as parameters may cause the URI to be dereferenced in response to user input. In this case, the security considerations of the URI specification apply. The widely deployed methods for submitting forms requests -- HTTP and SMTP -- provide little assurance of confidentiality. Information providers who request sensitive information via forms -- especially by way of the `PASSWORD' type input field (see 7.1.2, "Input Field: INPUT") -- should be aware and make their users aware of the lack of confidentiality. 4. Document Structure To identify information as an HTML document conforming to this specification, each document should start with the following prologue: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> NOTE - If the body of a `text/html' message entity does not begin with a document type declaration, an HTML user agent should infer the above document type declaration. HTML user agents are required to support the above document type declaration and the following document type declarations: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 2//EN"> <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN"> <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Strict//EN"> <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Strict//EN"> They are not required to support other document types, but they may. In particular, they may support other formal public identifiers, or other document types altogether. They may support an internal declaration subset with supplemental entity, element, and other markup declarations, or they may not. 4.1. Document Element: <HTML> The HTML document element consists of a head and a body, much like a memo or a mail message. The head contains the title and other optional elements. The body is a text flow consisting of paragraphs, lists, and other elements. 4.2. Head: <HEAD> The head of an HTML document is an unordered collection of information about the document. For example: <HEAD> <TITLE>Introduction to HTML</TITLE> </HEAD> 4.2.1. Title: <TITLE> Every HTML document must contain a <TITLE> element. The title should identify the contents of the document in a global context. A short title, such as ``Introduction'' may be meaningless out of context. A title such as ``Introduction to HTML Elements'' is more appropriate. NOTE - The length of a title is not limited; however, long titles may be truncated in some applications. To minimize this possibility, titles should be fewer than 64 characters. A user agent may display the title of a document in a history list or as a label for the window displaying the document. Contrast with headings (4.4, "Headings: H1 ... H6"), which are typically displayed with the body text flow. 4.2.2. Base URI: <BASE> The optional <BASE> element specifies the URI of the document, overriding any context otherwise known to the user agent. The required HREF attribute specifies the URI for navigating the document (see 6, "Hyperlinks"). The value of the HREF attribute must be an absolute URI. 4.2.3. Keyword Index: <ISINDEX> The <ISINDEX> element indicates that the user agent should allow the user to search an index by giving keywords. See 6.3, "Queries and Indexes" for details. 4.2.4. Link: <LINK> The <LINK> element represents a hyperlink. It is typically used to indicate authorship, related indexes and glossaries, older or more recent versions, stylesheets, document hierarchy etc. 4.2.5. Associated Metainformation: <META> The <META> element is an extensible container for use in identifying, indexing, and cataloging specialized document metainformation. Metainformation has two main functions: * to provide a means to discover that the data set exists and how it might be obtained or accessed; and * to document the content, quality, and features of a data set and so give an indication of its fitness for use. Each <META> element specifies a name/value pair. If multiple META elements are provided with the same name, their combined contents--concatenated as a comma-separated list--is the value associated with that name. NOTE - The <META> element should not be used where a specific element such as <TITLE> would be appropriate. HTTP servers should read the content of the document <HEAD> to generate header fields corresponding to any elements defining a value for the attribute HTTP-EQUIV. NOTE - The method by which the server extracts document metainformation is unspecified and not mandatory. The META element only provides an extensible mechanism for identifying and embedding document metainformation - how it may be used is up to the individual server implementation and the HTML user agent. Attributes of the META element: HTTP-EQUIV This attribute binds the element to an HTTP header field. An HTTP server may use this information to process the doducment. In particular, it should include a header field in the responses to GET requests for this document: the header name is taken from the HTTP-EQUIV attribute value, and the header value is taken from the value of the CONTENT attribute. HTTP header names are not case sensitive. NAME name of the name/value pair. If not present, HTTP-EQUIV gives the name. CONTENT The value of the name/value pair. Examples If the document contains: <META HTTP-EQUIV="Expires" CONTENT="1993年12月04日 21:29:02 GMT"> <meta http-equiv="Keywords" CONTENT="Fred, Barney"> <META HTTP-EQUIV="Reply-to" content="fielding@ics.uci.edu (Roy Fielding)"> then the server should include the following header fields: Expires: 1993年12月04日 21:29:02 GMT Keywords: Fred, Barney Reply-to: fielding@ics.uci.edu (Roy Fielding) as part of the HTTP response to a `GET' or `HEAD' request for that document. When the HTTP-EQUIV attribute is not present, the server should not generate an HTTP response header for the metainformation; e.g., Do not name an HTTP-EQUIV equal to a response header that should normally only be generated by the HTTP server. Example names that are inappropriate include `Server', `Date', and `Last-modified' -- the exact list of inappropriate names is dependent on the particular server implementation. 4.2.6. Next Id: <NEXTID> They <NEXTID> element gives a hint for the name to use for an <A> element when editing an HTML document. It should be distinct from all NAME attribute values on <A> elements. For example: <NEXTID N=Z27> 4.3. Body: <BODY> The <BODY> element contains the text flow of the document, including headings, paragraphs, lists, etc. For example: <BODY> <h1>Important Stuff</h1> <p>Explanation about important stuff... </BODY> 4.4. Headings: <H1> ... <H6> The six heading elements, <H1> through <H6>, denote section headings. Although the order and occurence of headings is not constrained by the HTML DTD, documents should not skip levels (for example, from H1 to H3), as converting such documents to other representations is often problematic. Example of use: <H1>This is a heading</H1> Here is some text <H2>Second level heading</H2> Here is some more text. Typical renderings are: H1 Bold, very-large font, centered. One or two blank lines above and below. H2 Bold, large font, flush-left. One or two blank lines above and below. H3 Italic, large font, slightly indented from the left margin. One or two blank lines above and below. H4 Bold, normal font, indented more than H3. One blank line above and below. H5 Italic, normal font, indented as H4. One blank line above. H6 Bold, indented same as normal text, more than H5. One blank line above. 4.5. Block Structuring Elements Each of the following elements defines a block structure; that is, they indicate a paragraph break before and after. 4.5.1. Paragraph: <P> The <P> element indicates a paragraph. The exact indentation, leading space, etc. of a paragraph is not specified and may be a function of other tags, style sheets, etc. Typically, paragraphs are surrounded by a vertical space of one line or half a line. The first line in a paragraph is indented in some cases. Example of use: <H1>This Heading Precedes the Paragraph</H1> <P>This is the text of the first paragraph. <P>This is the text of the second paragraph. Although you do not need to start paragraphs on new lines, maintaining this convention facilitates document maintenance.</P> <P>This is the text of a third paragraph.</P> 4.5.2. Preformatted Text: <PRE> The <PRE> element represents a character cell block of textand so is suitable for text that has been formatted on screen. The <PRE> tag may be used with the optional WIDTH attribute. The WIDTH attribute specifies the maximum number of characters for a line and allows the HTML user agent to select a suitable font and indentation. Within preformatted text: * Line breaks within the text are rendered as a move to the beginning of the next line. NOTE - References to the ``beginning of a new line'' do not imply that the renderer is forbidden from using a constant left indent for rendering preformatted text. The left indent may be constrained by the width required. * Anchor elements and phrase markup may be used. NOTE - Within a Preformatted Text element, the constraint that the rendering must be on a fixed horizontal character pitch may limit or prevent the ability of the HTML user agent to faithfully render phrase markup. * Elements that define paragraph formatting (headings, address, etc.) must not be used. NOTE - Som historical documents contain <P> tags in <PRE> elements. User agents are engcouraged to treat this a a line break. A <P> tag followed by a newline character should produce only one line break, not a line break plus a blank line. * The horizontal tab character (encoded in `US-ASCII' and `ISO-8859-1' as decimal 9) must be interpreted as the smallest positive nonzero number of spaces which will leave the number of characters so far on the line as a multiple of 8. Example of use: <PRE> This is an example line. </PRE> 4.5.3. Address: <ADDRESS> The <ADDRESS> element specifies such information as address, signature and authorship, often at the beginning or end of the body of a document. Typically, the <ADDRESS> element is rendered in an italic typeface and may be indented. Example of use: <ADDRESS> Newsletter editor<BR> J.R. Brown<BR> JimquickPost News, Jumquick, CT 01234<BR> Tel (123) 456 7890 </ADDRESS> 4.5.4. Block Quote: <BLOCKQUOTE> The <BLOCKQUOTE> element contains text quoted from another source. A typical rendering might be a slight extra left and right indent, and/or italic font. The <BLOCKQUOTE> typically provides space above and below the quote. Single-font rendition may reflect the quotation style of Internet mail by putting a vertical line of graphic characters, such as the greater than symbol (>), in the left margin. Example of use: I think the poem ends <BLOCKQUOTE> <P>Soft you now, the fair Ophelia. Nymph, in thy orisons, be all my sins remembered. </BLOCKQUOTE> but I am not sure. 4.6. List Elements HTML includes a number of list elements. They may be used in combination; for example, a <OL> may be nested in an <LI> element of a <UL>. 4.6.1. Unordered List: <UL>, <LI> The <UL> represents a list of items with no inherent ordering -- typically a bulleted list. The content of a <UL> element is a sequence of <LI> elements. For example: <UL> <LI>First list item <LI>Second list item <p>second paragraph of second item <LI>Third list item </UL> 4.6.2. Ordered List: <OL> The <UL> element represents an ordered list of items, sorted by sequence or order of importance. The content of a <OL> element is a sequence of <LI> elements. For example: <OL> <LI>Click the Web button to open the Open the URI window. <LI>Enter the URI number in the text field of the Open URI window. The Web document you specified is displayed. <ol> <li>substep 1 <li>substep 2 </ol> <LI>Click highlighted text to move from one link to another. </OL> The COMPACT attribute suggests that a compact rendering be used. 4.6.3. Directory List: <DIR> The <DIR> element is similar to the <UL> element. It represents a list of short items, typically up to 20 characters each. Items in a directory list may be arranged in columns, typically 24 characters wide. The content of a <OL> element is a sequence of <LI> elements. Nested block elements are not allowed in the content of <DIR> elements. For example: <DIR> <LI>A-H<LI>I-M <LI>M-R<LI>S-Z </DIR> 4.6.4. Menu List: <MENU> The <MENU> element is a list of items with typically one line per item. The menu list style is typically more compact than the style of an unordered list. The content of a <MENU> element is a sequence of <LI> elements. Nested block elements are not allowed in the content of <MENU> elements. For example: <MENU> <LI>First item in the list. <LI>Second item in the list. <LI>Third item in the list. </MENU> 4.6.5. Definition List: <DL>, <DT>, <DD> A definition list is a list of terms and corresponding definitions. Definition lists are typically formatted with the term flush-left and the definition, formatted paragraph style, indented after the term. Example of use: <DL> <DT>Term<DD>This is the definition of the first term. <DT>Term<DD>This is the definition of the second term. </DL> If the DT term does not fit in the DT column (one third of the display area), it may be extended across the page with the DD section moved to the next line, or it may be wrapped onto successive lines of the left hand column. The optional COMPACT attribute suggests that a compact rendering be used, because the list items are small and/or the entire list is large. Unless the COMPACT attribute is present, an HTML user agent may leave white space between successive DT, DD pairs. The COMPACT attribute may also reduce the width of the left-hand (DT) column. <DL COMPACT> <DT>Term<DD>This is the first definition in compact format. <DT>Term<DD>This is the second definition in compact format. </DL> 4.7. Phrase Markup Phrases may be marked up according to idiomatic usage, typographic appearance, or for use as hyperlink anchors. User agents must render highlighted phrases distinctly from plain text. Additionally, <EM> content must be rendered as distinct from <STRONG> content, and <B> content must rendered as distinct from <I> content. Phrase elements may be nested within the content of other phrase elements; however, HTML user agents may render nested phrase elements indistinctly from non-nested elements: plain <B>bold <I>italic</I></B> may the rendered the same as plain <B>bold </B><I>italic</I> 4.7.1. Idiomatic Elements 4.7.1.1. Citation: <CITE> The <CITE> element is used to indicate the title of a book or other citation. It is typically typeset as italics. For example: He just couldn't get enough of <cite>The Grapes of Wrath</cite>. 4.7.1.2. Code: <CODE> The <CODE> element indicates an example of code, typically rendered in a monospaced font. Contrast with the <PRE> block structuring element in 4.5.2, "Preformatted Text: PRE". For example: The expression <code>x += 1</code> is short for <code>x = x + 1</code>. 4.7.1.3. Emphasis: <EM> The <EM> element indicates an emphasized phrase, typically rendered as italics. For example: A singular subject <em>always</em> takes a singular verb. 4.7.1.4. Keyboard: <KBD> The Keyboard element indicates text typed by a user, typically rendered in a monospaced font. This is commonly used in instruction manuals. For example: Enter <kbd>FIND IT</kbd> to search the database. 4.7.1.5. Sample: <SAMP> The <SAMP> element indicates a sequence of literal characters, typically rendered in a monospaced font. For example: The only word containing the letters <samp>mt</samp> is dreamt. 4.7.1.6. Strong Empasis: <STRONG> The <STRONG> element indicates strong emphasis, typically rendered in bold. For example: <strong>STOP</strong>, or I'll say "<strong>STOP</strong>" again!. 4.7.1.7. Variable: <VAR> The <VAR> element indicates a placeholder, typically rendered as italic. For example: Take a guess: Roses are <var>blank</var>. 4.7.2. Typographic Elements Typographic elements are used to specify the format of marked text. Typical renderings for idomatic elements vary between user agents. If a specific rendering is necessary -- for example, when referring to a specific text attribute as in ``The italic parts are mandatory'' -- a typographic element can be used to ensure that the intended typography is used where possible. 4.7.2.1. Bold: <B> The <B> element indicated bold text. Where bold typography is unavailable, an alternative representation may be used. 4.7.2.2. Italic: <I> The <I> element indicated italic text. Where italic typography is unavailable, an alternative representation may be used. 4.7.2.3. Typewriter: <TT> The <TT> element indicates typewriter text. Where a typewriter font is unavailable, an alternative representation may be used. 4.7.3. Anchor: <A> The <A> element indicates the source and/or destination of a hyperlink (see 6, "Hyperlinks"). At least one of the NAME and HREF attributes should be given. Attributes of the <A> element: HREF gives the destination of a hyperlink. NAME gives the name of the anchor, and makes it available as a navigation destination. TITLE suggests a title for the destination resource -- advisory only. The TITLE attribute may be used: * for display prior to accessing the destination resource, for example, as a margin note or on a small box while the mouse is over the anchor, or while the document is being loaded; * for resources that do not specify a title such as graphics, plain text and Gopher menus, for use as a window title. REL The REL attribute gives the relationship(s) described by the hyperlink. The value is a whitespace separated list of relationship names. REV same as the REL attribute, but the semantics of the relationship are in the reverse direction. A link from A to B with REL=``X'' expresses the same relationship as a link from B to A with REV=``X''. An anchor may have both REL and REV attributes. URN specifies a preferred, more persistent identifier for the destination. The format of URNs is under discussion (1995) by various working groups of the Internet Engineering Task Force. METHODS specifies methods to be used in accessing the destination, as a whitespace-separated list of names. For similar reasons as for the TITLE attribute, it may be useful to include the information in advance in the link. For example, the HTML user agent may chose a different rendering as a function of the methods allowed; for example, something that is searchable may get a different icon. 4.8. Line Break: <BR> The <BR> element specifies a line break between words (see 5, "Character, Words, and Paragraphs"). For example: <P> Pease porridge hot<BR> Pease porridge cold<BR> Pease porridge in the pot<BR> Nine days old. 4.9. Horizontal Rule: <HR> The <HR> element is a divider between sections of text; typcially a full width horizontal rule or equivalent graphic. For example: <HR> <ADDRESS>February 8, 1995, CERN</ADDRESS> </BODY> 4.10. Image: <IMG> The <IMG> element refers to an image or icon. HTML user agents that cannot process images ignore the <IMG> element unless it the ALT attribute is present. NOTE - Some HTML user agents can process graphics linked via anchors , but not <IMG> graphics. If a graphic is essential, it should be referenced from an <A> element rather than in <IMG> element.If the graphic is not essential, then the <IMG> element is appropriate. Attributes of the <IMG> element: ALIGN alignment of the image with respect to the text baseline. * `TOP' specifies that the top of the image aligns with the tallest item on the line contianing the image. * `MIDDLE' specifies that the center of the image aligns with the baseline of the line containing the image. * `BOTTOM' specifies that the bottom of the image aligns with the baseline of the line containing the image. ALT Optional alternative text, for use in non-graphical environments. ISMAP indicates an image map (see 6.4, "Image Maps"). SRC specifies the URI of the image resource. NOTE - In practice, the media types of image resources are limited to a few raster graphic formats: typically `image/gif', `image/jpeg'. In particular, `text/html' resources are not intended to be used as image resources. Examples of use: <IMG SRC="triangle.xbm" ALT="Warning:"> Be sure to read these instructions. <IMG SRC="triangle.xbm">Be sure to read these instructions. <a href="http://machine/htbin/imagemap/sample"> <IMG SRC="sample.xbm" ISMAP> </a> 5. Character, Words, and Paragraphs An HTML user agent should present the body of an HTML document as a collection of typeset paragraphs and preformatted text. Except for the <PRE> element, each block structuring element is regarded as a paragraph by taking the data characters in its content and the content of its descendant elements, concatenating them, and splitting the result into words, separated by space, tab, or record end characters (and perhaps hyphen characters). The sequence of words is typeset as a paragraph by breaking it into lines. 5.1. The ISO Latin 1 Character Repertoire The minimum character repertoire supported by all conforming HTML user agents is Latin Alphabet Nr. 1, or simply Latin-1. Latin-1 includes characters from most Western European languages, as well as a number of control characters. Latin-1 also includes a non-breaking space, a soft hyphen indicator, 93 graphical characters, 8 unassigned characters, and 25 control characters. NOTE - Use the non-breaking space and soft hyphen indicator characters is discouraged because support for them is not widely deployed. NOTE - To support non-western writing systems, a larger character repertoire will be specified in a future version of HTML. The document character set will be ISO/IEC 10646-1, or some subset that agrees with ISO/IEC 10646-1; in particular, all numeric character references must use code positions assigned by ISO/IEC 10646-1. In SGML applications, the use of control characters is limited in order to maximize the chance of successful interchange over heterogeneous networks and operating systems. In HTML, only three control characters are allowed: Horizontal Tab (HT, encoded as 9 decimal in `US-ASCII' and `ISO-8859-1'), Carriage Return, and Line Feed. The HTML DTD references the Added Latin 1 entity set, to allow mnemonic representation of Latin 1 characters using only the widely supported ASCII character repertoire. For example: Kurt Gödel was a famous logician and mathematician. See 8.4.2, "ISO Latin 1 Character Entity Set" for a table of the ``Added Latin 1'' entities, and 11.1, "The ANSI/ISO 8859-1 Coded Character Set" for a table of the code positions of ANSI/ISO 8859-1. 6. Hyperlinks In addition to general purpose elements such as paragraphs and lists, HTML documents can express hyperlinks. A hyperlink is a relationship between two resources, called the source and the destination of the hyperlink. Each resource has a Uniform Resource Identifier (URI). An HTML user agent allows navigating a collection of these resources. In the following interactions, the URI of the source document is called the base URI. 6.1. Accessing Resources Each of the following markup constructs is the source of a hyperlink; these hyperlinks are references to resources to be processed in conjunction with the source documents: * <IMG> elements * <INPUT> elements with the SRC attribute present * <LINK> element To access the destination of a hyperlink, the base URI of the source document is combined with the value of the HREF or SRC attribute of the hyperlink element according to [RELURL]. The user agent disregards any fragment identifer, and uses the resulting URI to access the destination resource. For example, if a document identified as `http://host/x/y.html' contains: <img src="../icons/abc.gif"> then the user agent must use the URI `http://host/icons/abc.gif' to access the resource linked from the <IMG> element. 6.2. Traversing Hyperlinks An <A> element with the HREF attribute present is an anchor; that is, the source of a hyperlink that is an option to navigate to another resource. The <LINK> element may also be an anchor. In addition to the base URI, the state of an HTML user agent includes a list of the anchors in the document. The user can traverse a hyperlink by choosing an anchor. The user agent then accesses the destination document as above and presents it. 6.2.1. Fragment Identifiers If the value of the <HREF> attribute of an anchor element contains a `#' character, then the characters after the `#' are a fragment identifier, not a part of the destination URI. As a degenerate case, `HREF="#fragment"' refers to an anchor in the same document: the source and destination URIs are the same. After accessing the destination resource, the navigation state (the scrollbar, for example) may be modified by a fragment identifer in the hyperlink source markup. The meaning of fragment identifiers depends on the media type of the destination resource. For `text/html' resources, it instructs the user agent to locate the <A> element with a NAME attribute whose value is the same as the fragment identifier. The matching is case sensitive. For example, if a user agent was processing the above document and the user indicated the following anchor: <p> See: <a href="app1.html#bannanas">appendix 1</a> for more detail on bannanas.</a> then the user agent URI must access the resource `http://host/x/app1.html'. Assuming the resource is represented using the `text/html' media type, the user agent must locate the anchor named `bannanas' and begin navigation there. The base URI for navigating the destination document may be different from the URI used to access it. For example, it may be replaced by by a <BASE> tag in the destination document or by an HTTP redirection transaction. 6.3. Queries and Indexes The <ISINDEX> element represents a set of hyperlinks. The user can choose from the set by providing keywords to the user agent. The user agent computes the destination URI by appending `?' and the keywords to the base URI. The keywords are escaped according to [URL] and joined by `+'. For example, if a document contains: <BASE HREF="http://host/index"> <ISINDEX> and the user provides the keywords `apple' and `berry', then the user agent must access the resource `http://host/index?apple+berry'. <FORM> elements with `METHOD=GET' also represent sets of hyperlinks. See 7.2.2, "Query Forms: METHOD=GET" for details. 6.4. Image Maps The ISMAP attribute in combination with the <A> and <IMG> elements, represents a set of hyperlinks. The user can choose from the set by choosing a pixel of the image. The user agent computes the destination URI by appending `?' and the coordinates of the pixel to the URI given in the <A> element. For example, if a document contains: <head><title>ImageMap Example</title> <BASE HREF="http://host/index"></head> <body> <p> Choose any of these icons:<br> <a href="/cgi-bin/imagemap"><img ismap src="icons.gif"></a> and the user chooses the upper-leftmost pixel, then chosen hyperlink is the one with the URI `http://host/cgi-bin/image?0,0'. 7. Forms A form is a template for a form data set -- sequence of name/value pair fields -- with an associated method and action URI. The names are specified on the NAME attributes of form input elements, and the values are given by the user. The resulting form data set is used to access an information service as a function of the action and method. Forms elements can be mixed in with document structuring elements. For example, a <PRE> element may contain a <FORM> element, or a <FORM> element may contain lists which contain <INPUT> elements. This gives considerable flexibility in designing the layout of forms. Form processing is a level 2 feature. 7.1. Form Elements 7.1.1. Form: <FORM> The <FORM> element contains a sequence of input elements, along with document structuring elements. The attributes are: ACTION specifies the action URI for the form. The ACTION attribute defaults to the base URI of the document (see 6, "Hyperlinks"). METHOD selects a method of accessing the action URI. ENCTYPE specifies the media type used to encode the name/value pairs for transport, in case the protocol does not itself impose a format. 7.1.2. Input Field: <INPUT> The <INPUT> element represents a field for user input. Attributes are: ALIGN vertical alignment of the image. For use only with `TYPE=IMAGE'. The possible values are as for the ALIGN attribute of the <IMG> element (see 4.10, "Image: IMG"). CHECKED indicates that the initial state of a checkbox or radio button is selected. MAXLENGTH constrains the number of characters that can be entered into a text input field. If the value of MAXLENGTH is greater the the value of the SIZE attribute, the field should scroll appropriately. The default number of characters is unlimited. NAME symbolic name for the form field corresponding to this element or group of elements. SIZE specifies the amount of display space allocated to this input field according to its type. SRC A URI specifying an image resource. For use only with `TYPE=IMAGE'. TYPE indicates type of the field. Defaults to `TEXT'. Values are: CHECKBOX an independent boolean value. HIDDEN a hidden field. The user does not interact with this field; instead, the VALUE attribute can be used to specify a value. IMAGE specifies an image resource to display, and allows input of two form data: the x and y coordinate of a pixel chosen from the image. The names of the data are the name of this element with `.x' and `.y' appended. `TYPE=IMAGE' implies `TYPE=SUBMIT' processing; that is, when a pixel is chosen, the form as a whole is submitted. PASSWORD Similar to the TEXT attribute, except that the value is obscured as it is entered. RADIO a 1-of-many choice. All <INPUT> elements with `TYPE=RADIO' and the same NAME combine into one form field. The value of the form field is the VALUE of the element chosen by the user. The initial state may be indicated with the CHECKED attribute. The VALUE attribute is required for radio inputs. RESET an input option, typically a button, that instructs the user agent to reset the form's fields to their initial states. Any VALUE attribute indicates a label for the input (button). SUBMIT an input option, typically a button, that instructs the user agent to submit the form. Any VALUE attribute indicates a label for the input (button). If the NAME attribute is present, this element contributes a form field whose value is given by the VALUE attribute. If the NAME attribute is not present, this element does not contribute a form field. TEXT a single line text entry fields. The SIZE and MAXLENGTH attributes may be used to constrain the input or layout of the field. Use the <TEXTAREA> element for mulit-line text fields. VALUE The initial value of the field. 7.1.3. Selection: <SELECT> The <SELECT> element constrains the form field to an enumerated list of values. The values are given in <OPTION> elements. Attributes are: MULTIPLE indicates that more than one option may be included in the value. NAME specifies the name of the form field. SIZE specifies the number of visible items. Select fields of size one are typically pop-down menus, whereas select fields with size greater than one are typically lists. For example: <SELECT NAME="flavor"> <OPTION>Vanilla <OPTION>Strawberry <OPTION>Rum and Raisin <OPTION>Peach and Orange </SELECT> The initial state has the first option selected, unless a SELECTED attribute is present on any of the <OPTION> elements. 7.1.3.1. Option: <OPTION> The Option element can only occur within a Select element. It represents one choice, and has the following attributes: SELECTED Indicates that this option is initially selected. VALUE indicates the value to be returned if this option is chosen. The field value defaults to the content of the <OPTION> element. The content of the <OPTION> element is presented to the user to represent the option. It is used as a returned value if the VALUE attribute is not present. 7.1.4. Text Area: <TEXTAREA> The <TEXTAREA> element represents a multi-line text field. For example: <TEXTAREA NAME="address" ROWS=64 COLS=6> HaL Computer Systems 1315 Dell Avenue Campbell, California 95008 </TEXTAREA> The content of the <TEXTAREA> element is the field's initial value. Typically, the ROWS and COLS attributes determine the visible dimension of the field in characters. The field is rendered in a fixed-width font. HTML user agents should allow text to extend beyond these limits by scrolling as needed. 7.2. Form Submission An HTML user agent begins processing a form by presenting the document with the fields in their initial state. The user is allowed to modify the fields, constrained by the field type etc. When the user indicates that the form should be submitted (using a submit button or image input), the form data set is processed according to its method, action URI and enctype. When there is only one single-line text input field in a form, the user agent should accept Enter in that field as a request to submit the form. 7.2.1. The `application/x-www-form-urlencoded' Media Type The default encoding for all forms is `application/x-www-form-urlencoded'. A form data set is represented in this media type as follows: 1. The form field names and values are escaped: space characterss are replaced by `+', and then reserved characters are escaped as per [URL]; that is, non-alphanumeric characters are replaced by `%HH', a percent sign and two hexadecimal digits representing the ASCII code of the character. Line breaks, as in multi-line textfield values, are represented as CR LF pairs, i.e. `%0D0A'. 2. The fields are listed in the order they appear in the document with the name separated from the value by `=' and the pairs separated from each other by `&'. Fields with null values may be omitted. In particular, unselected radio buttons and checkboxes should not appear in the encoded data, but hidden fields with VALUE attributes present should. NOTE - The URI from a query form submission can be used in a normal anchor style hyperlink. Unfortunately, the use of the `&' character to separate form fields interacts with its use in SGML attribute values as an entity reference delimiter. For example, the URI `http://host/?x=1&y=2' must be written `<a href="http://host/?x=1&y=2"' or `<a href="http://host/?x=1&#amp;y=2">'. HTTP server implementors, and in particular, CGI implementors are encouraged to support the use of `;' in place of `&' to save users the trouble of escaping `&' characters this way. 7.2.2. Query Forms: `METHOD=GET' If the processing of a form is idempotent (i.e. it has no lasting observable effect on the state of the world), then the form method should be `GET'. Many database searches have no visible side-effects and make ideal applications of query forms. To process a form whose action URL is an HTTP URL and whose method is `GET', the user agent starts with the action URI and appends a `?' and the form data set, in `application/x-www-form-urlencoded' format as above. The user agent then traverses the link to this URI just as if it were an anchor (see 6.2, "Traversing Hyperlinks"). NOTE - The URL encoding may result in vary long URIs, which cause some historical HTTP server implementations to exhibit defective behavior. As a result, some HTML forms are written using `METHOD=POST' even though the form submission has no side-effects. 7.2.3. Forms with Side-Effects: `METHOD=POST' If the service associated with the processing of a form has side effects (for example, modification of a database or subscription to a service), the method should be `POST'. To process a form whose action URL is an HTTP URL and whose method is `POST', the user agent conducts an HTTP POST transaction using the action URI, and a message body of type `application/x-www-form-urlencoded' format as above. The user agent should display the response from the HTTP POST interaction just as it would display the response from an HTTP GET above. 7.2.4. Example Form Submission: Questionnaire Form Consider the following document: <title>Sample of HTML Form Submission</title> <H1>Sample Questionnaire</H1> <P>Please fill out this questionnaire: <FORM METHOD="POST" ACTION="http://www.w3.org/sample"> <P>Your name: <INPUT NAME="name" size="48"> <P>Male <INPUT NAME="gender" TYPE=RADIO VALUE="male"> <P>Female <INPUT NAME="gender" TYPE=RADIO VALUE="female"> <P>Number in family: <INPUT NAME="family" TYPE=text> <P>Cities in which you maintain a residence: <UL> <LI>Kent <INPUT NAME="city" TYPE=checkbox VALUE="kent"> <LI>Miami <INPUT NAME="city" TYPE=checkbox VALUE="miami"> <LI>Other <TEXTAREA NAME="other" cols=48 rows=4></textarea> </UL> Nickname: <INPUT NAME="nickname" SIZE="42"> <P>Thank you for responding to this questionnaire. <P><INPUT TYPE=SUBMIT> <INPUT TYPE=RESET> </FORM> The inital state of the form data set is: name ``'' gender ``male'' family ``'' other ``'' nickname ``'' Note that the radio input has an initial value, while the checkbox has none. The user might edit the fields and request that the form be submitted. At that point, suppose the values are: name ``John Doe'' gender ``male'' family ``5'' city ``kent,miami'' other ``abc\ndef'' nickname ``J&D'' The user agent then conducts an HTTP POST transaction using the URI `http://www.w3.org/sample'. The message body would be (ignore the linebreak): name=John+Doe&gender=male&family=5&city=kent%2Cmiami& other=abc%0D0Adef&nickname=J%26D 8. HTML Public Text 8.1. HTML DTD This is the Document Type Definition for the HyperText Markup Language. <!-- html.dtd Document Type Definition for the HyperText Markup Language (HTML DTD) $Id: html.dtd,v 1.25 1995年03月29日 18:53:13 connolly Exp $ Author: Daniel W. Connolly <connolly@w3.org> See Also: html.decl, html-0.dtd, html-1.dtd http://info.cern.ch/hypertext/WWW/MarkUp/MarkUp.html --> <!ENTITY % HTML.Version "-//IETF//DTD HTML 2.0//EN" -- Typical usage: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> <html> ... </html> -- > <!--============ Feature Test Entities ========================--> <!ENTITY % HTML.Recommended "IGNORE" -- Certain features of the language are necessary for compatibility with widespread usage, but they may compromise the structural integrity of a document. This feature test entity enables a more prescriptive document type definition that eliminates those features. --> <![ %HTML.Recommended [ <!ENTITY % HTML.Deprecated "IGNORE"> ]]> <!ENTITY % HTML.Deprecated "INCLUDE" -- Certain features of the language are necessary for compatibility with earlier versions of the specification, but they tend to be used an implemented inconsistently, and their use is deprecated. This feature test entity enables a document type definition that eliminates these features. --> <!ENTITY % HTML.Highlighting "INCLUDE" -- Use this feature test entity to validate that a document uses no highlighting tags, which may be ignored on minimal implementations. --> <!ENTITY % HTML.Forms "INCLUDE" -- Use this feature test entity to validate that a document contains no forms, which may not be supported in minimal implementations --> <!--============== Imported Names ==============================--> <!ENTITY % Content-Type "CDATA" -- meaning an internet media type (aka MIME content type, as per RFC1521) --> <!ENTITY % HTTP-Method "GET | POST" -- as per HTTP specification, in progress --> <!ENTITY % URI "CDATA" -- The term URI means a CDATA attribute whose value is a Uniform Resource Identifier, as defined by "Universal Resource Identifiers" by Tim Berners-Lee aka RFC 1630 Note that CDATA attributes are limited by the LITLEN capacity (1024 in the current version of html.decl), so that URIs in HTML have a bounded length. --> <!--========= DTD "Macros" =====================--> <!ENTITY % heading "H1|H2|H3|H4|H5|H6"> <!ENTITY % list " UL | OL | DIR | MENU " > <!--======= Character mnemonic entities =================--> <!ENTITY % ISOlat1 PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML"> %ISOlat1; <!ENTITY amp CDATA "&" -- ampersand --> <!ENTITY gt CDATA ">" -- greater than --> <!ENTITY lt CDATA "<" -- less than --> <!ENTITY quot CDATA """ -- double quote --> <!--========= SGML Document Access (SDA) Parameter Entities =====--> <!-- HTML 2.0 contains SGML Document Access (SDA) fixed attributes in support of easy transformation to the International Committee for Accessible Document Design (ICADD) DTD "-//EC-USA-CDA/ICADD//DTD ICADD22//EN". ICADD applications are designed to support usable access to structured information by print-impaired individuals through Braille, large print and voice synthesis. For more information on SDA & ICADD: - ISO 12083:1993, Annex A.8, Facilities for Braille, large print and computer voice - ICADD ListServ <ICADD%ASUACAD.BITNET@ARIZVM1.ccit.arizona.edu> - Usenet news group bit.listserv.easi - Recording for the Blind, +1 800 221 4792 --> <!ENTITY % SDAFORM "SDAFORM CDATA #FIXED" -- one to one mapping --> <!ENTITY % SDARULE "SDARULE CDATA #FIXED" -- context-sensitive mapping --> <!ENTITY % SDAPREF "SDAPREF CDATA #FIXED" -- generated text prefix --> <!ENTITY % SDASUFF "SDASUFF CDATA #FIXED" -- generated text suffix --> <!ENTITY % SDASUSP "SDASUSP NAME #FIXED" -- suspend transform process --> <!--========== Text Markup =====================--> <![ %HTML.Highlighting [ <!ENTITY % font " TT | B | I "> <!ENTITY % phrase "EM | STRONG | CODE | SAMP | KBD | VAR | CITE "> <!ENTITY % text "#PCDATA | A | IMG | BR | %phrase | %font"> <!ELEMENT (%font;|%phrase) - - (%text)*> <!ATTLIST ( TT | CODE | SAMP | KBD | VAR ) %SDAFORM; "Lit" > <!ATTLIST ( B | STRONG ) %SDAFORM; "B" > <!ATTLIST ( I | EM | CITE ) %SDAFORM; "It" > <!-- <TT> Typewriter text --> <!-- <B> Bold text --> <!-- <I> Italic text --> <!-- <EM> Emphasized phrase --> <!-- <STRONG> Strong emphais --> <!-- <CODE> Source code phrase --> <!-- <SAMP> Sample text or characters --> <!-- <KBD> Keyboard phrase, e.g. user input --> <!-- <VAR> Variable phrase or substituable --> <!-- <CITE> Name or title of cited work --> <!ENTITY % pre.content "#PCDATA | A | HR | BR | %font | %phrase"> ]]> <!ENTITY % text "#PCDATA | A | IMG | BR"> <!ELEMENT BR - O EMPTY> <!ATTLIST BR %SDAPREF; "&#RE;" > <!-- <BR> Line break --> <!--========= Link Markup ======================--> <![ %HTML.Recommended [ <!ENTITY % linkName "ID"> ]]> <!ENTITY % linkName "CDATA"> <!ENTITY % linkType "NAME" -- a list of these will be specified at a later date --> <!ENTITY % linkExtraAttributes "REL %linkType #IMPLIED REV %linkType #IMPLIED URN CDATA #IMPLIED TITLE CDATA #IMPLIED METHODS NAMES #IMPLIED "> <![ %HTML.Recommended [ <!ENTITY % A.content "(%text)*" -- <H1><a name="xxx">Heading</a></H1> is preferred to <a name="xxx"><H1>Heading</H1></a> --> ]]> <!ENTITY % A.content "(%heading|%text)*"> <!ELEMENT A - - %A.content -(A)> <!ATTLIST A HREF %URI #IMPLIED NAME %linkName #IMPLIED %linkExtraAttributes; %SDAPREF; "<Anchor: #AttList>" > <!-- <A> Anchor; source/destination of link --> <!-- <A NAME="..."> Name of this anchor --> <!-- <A HREF="..."> Address of link destination --> <!-- <A URN="..."> Permanent address of destination --> <!-- <A REL=...> Relationship to destination --> <!-- <A REV=...> Relationship of destination to this --> <!-- <A TITLE="..."> Title of destination (advisory) --> <!-- <A METHODS="..."> Operations on destination (advisory) --> <!--========== Images ==========================--> <!ELEMENT IMG - O EMPTY> <!ATTLIST IMG SRC %URI; #REQUIRED ALT CDATA #IMPLIED ALIGN (top|middle|bottom) #IMPLIED ISMAP (ISMAP) #IMPLIED %SDAPREF; "<Fig><?SDATrans Img: #AttList>#AttVal(Alt)</Fig>" > <!-- <IMG> Image; icon, glyph or illustration --> <!-- <IMG SRC="..."> Address of image object --> <!-- <IMG ALT="..."> Textual alternative --> <!-- <IMG ALIGN=...> Position relative to text --> <!-- <IMG ISMAP> Each pixel can be a link --> <!--========== Paragraphs=======================--> <!ELEMENT P - O (%text)*> <!ATTLIST P %SDAFORM; "Para" > <!-- <P> Paragraph --> <!--========== Headings, Titles, Sections ===============--> <!ELEMENT HR - O EMPTY> <!ATTLIST HR %SDAPREF; "&#RE;&#RE;" > <!-- <HR> Horizontal rule --> <!ELEMENT ( %heading ) - - (%text;)*> <!ATTLIST H1 %SDAFORM; "H1" > <!ATTLIST H2 %SDAFORM; "H2" > <!ATTLIST H3 %SDAFORM; "H3" > <!ATTLIST H4 %SDAFORM; "H4" > <!ATTLIST H5 %SDAFORM; "H5" > <!ATTLIST H6 %SDAFORM; "H6" > <!-- <H1> Heading, level 1 --> <!-- <H2> Heading, level 2 --> <!-- <H3> Heading, level 3 --> <!-- <H4> Heading, level 4 --> <!-- <H5> Heading, level 5 --> <!-- <H6> Heading, level 6 --> <!--========== Text Flows ======================--> <![ %HTML.Forms [ <!ENTITY % block.forms "BLOCKQUOTE | FORM | ISINDEX"> ]]> <!ENTITY % block.forms "BLOCKQUOTE"> <![ %HTML.Deprecated [ <!ENTITY % preformatted "PRE | XMP | LISTING"> ]]> <!ENTITY % preformatted "PRE"> <!ENTITY % block "P | %list | DL | %preformatted | %block.forms"> <!ENTITY % flow "(%text|%block)*"> <!ENTITY % pre.content "#PCDATA | A | HR | BR"> <!ELEMENT PRE - - (%pre.content)*> <!ATTLIST PRE WIDTH NUMBER #implied %SDAFORM; "Lit" > <!-- <PRE> Preformatted text --> <!-- <PRE WIDTH=...> Maximum characters per line --> <![ %HTML.Deprecated [ <!ENTITY % literal "CDATA" -- historical, non-conforming parsing mode where the only markup signal is the end tag in full --> <!ELEMENT (XMP|LISTING) - - %literal> <!ATTLIST XMP %SDAFORM; "Lit" %SDAPREF; "Example:&#RE;" > <!ATTLIST LISTING %SDAFORM; "Lit" %SDAPREF; "Listing:&#RE;" > <!-- <XMP> Example section --> <!-- <LISTING> Computer listing --> <!ELEMENT PLAINTEXT - O %literal> <!-- <PLAINTEXT> Plain text passage --> <!ATTLIST PLAINTEXT %SDAFORM; "Lit" > ]]> <!--========== Lists ==================--> <!ELEMENT DL - - (DT | DD)+> <!ATTLIST DL COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "Definition List:" > <!ELEMENT DT - O (%text)*> <!ATTLIST DT %SDAFORM; "Term" > <!ELEMENT DD - O %flow> <!ATTLIST DD %SDAFORM; "LItem" > <!-- <DL> Definition list, or glossary --> <!-- <DL COMPACT> Compact style list --> <!-- <DT> Term in definition list --> <!-- <DD> Definition of term --> <!ELEMENT (OL|UL) - - (LI)+> <!ATTLIST OL COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" > <!ATTLIST UL COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" > <!-- <UL> Unordered list --> <!-- <UL COMPACT> Compact list style --> <!-- <OL> Ordered, or numbered list --> <!-- <OL COMPACT> Compact list style --> <!ELEMENT (DIR|MENU) - - (LI)+ -(%block)> <!ATTLIST DIR COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Directory</LHead>" > <!ATTLIST MENU COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Menu</LHead>" > <!-- <DIR> Directory list --> <!-- <DIR COMPACT> Compact list style --> <!-- <MENU> Menu list --> <!-- <MENU COMPACT> Compact list style --> <!ELEMENT LI - O %flow> <!ATTLIST LI %SDAFORM; "LItem" > <!-- <LI> List item --> <!--========== Document Body ===================--> <![ %HTML.Recommended [ <!ENTITY % body.content "(%heading|%block|HR|ADDRESS|IMG)*" -- <h1>Heading</h1> <p>Text ... is preferred to <h1>Heading</h1> Text ... --> ]]> <!ENTITY % body.content "(%heading | %text | %block | HR | ADDRESS)*"> <!ELEMENT BODY O O %body.content> <!-- <BODY> Document body --> <!ELEMENT BLOCKQUOTE - - %body.content> <!ATTLIST BLOCKQUOTE %SDAFORM; "BQ" > <!-- <BLOCKQUOTE> Quoted passage --> <!ELEMENT ADDRESS - - (%text|P)*> <!ATTLIST ADDRESS %SDAFORM; "Lit" %SDAPREF; "Address:&#RE;" > <!-- <ADDRESS> Address, signature, or byline --> <!--======= Forms ====================--> <![ %HTML.Forms [ <!ELEMENT FORM - - %body.content -(FORM) +(INPUT|SELECT|TEXTAREA)> <!ATTLIST FORM ACTION %URI #IMPLIED METHOD (%HTTP-Method) GET ENCTYPE %Content-Type; "application/x-www-form-urlencoded" %SDAPREF; "<Para>Form:</Para>" %SDASUFF; "<Para>Form End.</Para>" > <!-- <FORM> Fill-out or data-entry form --> <!-- <FORM ACTION="..."> Address for completed form --> <!-- <FORM METHOD=...> Method of submitting form --> <!-- <FORM ENCTYPE="..."> Representation of form data --> <!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX | RADIO | SUBMIT | RESET | IMAGE | HIDDEN )"> <!ELEMENT INPUT - O EMPTY> <!ATTLIST INPUT TYPE %InputType TEXT NAME CDATA #IMPLIED VALUE CDATA #IMPLIED SRC %URI #IMPLIED CHECKED (CHECKED) #IMPLIED SIZE CDATA #IMPLIED MAXLENGTH NUMBER #IMPLIED ALIGN (top|middle|bottom) #IMPLIED %SDAPREF; "Input: " > <!-- <INPUT> Form input datum --> <!-- <INPUT TYPE=...> Type of input interaction --> <!-- <INPUT NAME=...> Name of form datum --> <!-- <INPUT VALUE="..."> Default/initial/selected value --> <!-- <INPUT SRC="..."> Address of image --> <!-- <INPUT CHECKED> Initial state is "on" --> <!-- <INPUT SIZE=...> Field size hint --> <!-- <INPUT MAXLENGTH=...> Data length maximum --> <!-- <INPUT ALIGN=...> Image alignment --> <!ELEMENT SELECT - - (OPTION+) -(INPUT|SELECT|TEXTAREA)> <!ATTLIST SELECT NAME CDATA #REQUIRED SIZE NUMBER #IMPLIED MULTIPLE (MULTIPLE) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Select #AttVal(Multiple)</LHead>" > <!-- <SELECT> Selection of option(s) --> <!-- <SELECT NAME=...> Name of form datum --> <!-- <SELECT SIZE=...> Options displayed at a time --> <!-- <SELECT MULTIPLE> Multiple selections allowed --> <!ELEMENT OPTION - O (#PCDATA)*> <!ATTLIST OPTION SELECTED (SELECTED) #IMPLIED VALUE CDATA #IMPLIED %SDAFORM; "LItem" %SDAPREF; "Option: #AttVal(Value) #AttVal(Selected)" > <!-- <OPTION> A selection option --> <!-- <OPTION SELECTED> Initial state --> <!-- <OPTION VALUE="..."> Form datum value for this option--> <!ELEMENT TEXTAREA - - (#PCDATA)* -(INPUT|SELECT|TEXTAREA)> <!ATTLIST TEXTAREA NAME CDATA #REQUIRED ROWS NUMBER #REQUIRED COLS NUMBER #REQUIRED %SDAFORM; "Para" %SDAPREF; "Input Text -- #AttVal(Name): " > <!-- <TEXTAREA> An area for text input --> <!-- <TEXTAREA NAME=...> Name of form datum --> <!-- <TEXTAREA ROWS=...> Height of area --> <!-- <TEXTAREA COLS=...> Width of area --> ]]> <!--======= Document Head ======================--> <![ %HTML.Recommended [ <!ENTITY % head.extra "META* & LINK*"> ]]> <!ENTITY % head.extra "NEXTID? & META* & LINK*"> <!ENTITY % head.content "TITLE & ISINDEX? & BASE? & (%head.extra)"> <!ELEMENT HEAD O O (%head.content)> <!-- <HEAD> Document head --> <!ELEMENT TITLE - - (#PCDATA)*> <!ATTLIST TITLE %SDAFORM; "Ti" > <!-- <TITLE> Title of document --> <!ELEMENT LINK - O EMPTY> <!ATTLIST LINK HREF %URI #REQUIRED %linkExtraAttributes; %SDAPREF; "Linked to : #AttVal (TITLE) (URN) (HREF)>" > <!-- <LINK> Link from this document --> <!-- <LINK HREF="..."> Address of link destination --> <!-- <LINK URN="..."> Lasting name of destination --> <!-- <LINK REL=...> Relationship to destination --> <!-- <LINK REV=...> Relationship of destination to this --> <!-- <LINK TITLE="..."> Title of destination (advisory) --> <!-- <LINK METHODS="..."> Operations allowed (advisory) --> <!ELEMENT ISINDEX - O EMPTY> <!ATTLIST ISINDEX %SDAPREF; "<Para>[Document is indexed/searchable.]</Para>"> <!-- <ISINDEX> Document is a searchable index --> <!ELEMENT BASE - O EMPTY> <!ATTLIST BASE HREF %URI; #REQUIRED > <!-- <BASE> Base context document --> <!-- <BASE HREF="..."> Address for this document --> <!ELEMENT NEXTID - O EMPTY> <!ATTLIST NEXTID N %linkName #REQUIRED > <!-- <NEXTID> Next ID to use for link name --> <!-- <NEXTID N=...> Next ID to use for link name --> <!ELEMENT META - O EMPTY> <!ATTLIST META HTTP-EQUIV NAME #IMPLIED NAME NAME #IMPLIED CONTENT CDATA #REQUIRED > <!-- <META> Generic Metainformation --> <!-- <META HTTP-EQUIV=...> HTTP response header name --> <!-- <META NAME=...> Metainformation name --> <!-- <META CONTENT="..."> Associated information --> <!--======= Document Structure =================--> <![ %HTML.Deprecated [ <!ENTITY % html.content "HEAD, BODY, PLAINTEXT?"> ]]> <!ENTITY % html.content "HEAD, BODY"> <!ELEMENT HTML O O (%html.content)> <!ENTITY % version.attr "VERSION CDATA #FIXED '%HTML.Version;'"> <!ATTLIST HTML %version.attr; %SDAFORM; "Book" > <!-- <HTML> HTML Document --> 8.2. SGML Declaration for HTML This is the SGML Declaration for HyperText Markup Language (HTML) as used by the World Wide Web (WWW) application: <!SGML "ISO 8879:1986" -- SGML Declaration for HyperText Markup Language (HTML). -- CHARSET BASESET "ISO 646:1983//CHARSET International Reference Version (IRV)//ESC 2/5 4/0" DESCSET 0 9 UNUSED 9 2 9 11 2 UNUSED 13 1 13 14 18 UNUSED 32 95 32 127 1 UNUSED BASESET "ISO Registration Number 100//CHARSET ECMA-94 Right Part of Latin Alphabet Nr. 1//ESC 2/13 4/1" DESCSET 128 32 UNUSED 160 96 32 CAPACITY SGMLREF TOTALCAP 150000 GRPCAP 150000 ENTCAP 150000 SCOPE DOCUMENT SYNTAX SHUNCHAR CONTROLS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127 BASESET "ISO 646:1983//CHARSET International Reference Version (IRV)//ESC 2/5 4/0" DESCSET 0 128 0 FUNCTION RE 13 RS 10 SPACE 32 TAB SEPCHAR 9 NAMING LCNMSTRT "" UCNMSTRT "" LCNMCHAR ".-" UCNMCHAR ".-" NAMECASE GENERAL YES ENTITY NO DELIM GENERAL SGMLREF SHORTREF SGMLREF NAMES SGMLREF QUANTITY SGMLREF ATTSPLEN 2100 LITLEN 1024 NAMELEN 72 -- somewhat arbitrary; taken from internet line length conventions -- PILEN 1024 TAGLEN 2100 GRPGTCNT 150 GRPCNT 64 FEATURES MINIMIZE DATATAG NO OMITTAG YES RANK NO SHORTTAG YES LINK SIMPLE NO IMPLICIT NO EXPLICIT NO OTHER CONCUR NO SUBDOC NO FORMAL YES APPINFO "SDA" -- conforming SGML Document Access application -- > <!-- $Id: html.decl,v 1.15 1995年05月06日 01:44:47 connolly Exp $ Author: Daniel W. Connolly <connolly@hal.com> See also: http://www.hal.com/%7Econnolly/html-spec http://info.cern.ch/hypertext/WWW/MarkUp/MarkUp.html --> 8.3. Sample SGML Open Entity Catalog for HTML The SGML standard describes an ``entity manager'' as the portion or component of an SGML system that maps SGML entities into the actual storage model (e.g., the file system). The standard itself does not define a particular mapping methodology or notation. To assist the interoperability among various SGML tools and systems, the SGML Open consortium has passed a technical resolution that defines a format for an application- independent entity catalog that maps external identifiers and/or entity names to file names. Each entry in the catalog associates a storage object identifier (such as a file name) with information about the external entity that appears in the SGML document. In addition to entries that associate public identifiers, a catalog entry can associate an entity name with a storage object indentifier. For example, the following are possible catalog entries: -- catalog: SGML Open style entity catalog for HTML -- -- $Id: catalog,v 1.2 1994年11月30日 23:45:18 connolly Exp $ -- -- Ways to refer to Level 2: most general to most specific -- PUBLIC "-//IETF//DTD HTML//EN" html.dtd PUBLIC "-//IETF//DTD HTML 2.0//EN" html.dtd PUBLIC "-//IETF//DTD HTML Level 2//EN" html.dtd PUBLIC "-//IETF//DTD HTML 2.0 Level 2//EN" html.dtd -- Ways to refer to Level 1: most general to most specific -- PUBLIC "-//IETF//DTD HTML Level 1//EN" html-1.dtd PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN" html-1.dtd -- Ways to refer to Level 0: most general to most specific -- PUBLIC "-//IETF//DTD HTML Level 0//EN" html-0.dtd PUBLIC "-//IETF//DTD HTML 2.0 Level 0//EN" html-0.dtd -- Ways to refer to Strict Level 2: most general to most specific -- PUBLIC "-//IETF//DTD HTML Strict//EN" html-s.dtd PUBLIC "-//IETF//DTD HTML 2.0 Strict//EN" html-s.dtd PUBLIC "-//IETF//DTD HTML Strict Level 2//EN" html-s.dtd PUBLIC "-//IETF//DTD HTML 2.0 Strict Level 2//EN" html-s.dtd -- Ways to refer to Strict Level 1: most general to most specific -- PUBLIC "-//IETF//DTD HTML Strict Level 1//EN" html-1s.dtd PUBLIC "-//IETF//DTD HTML 2.0 Strict Level 1//EN" html-1s.dtd -- Ways to refer to Strict Level 0: most general to most specific -- PUBLIC "-//IETF//DTD HTML Strict Level 0//EN" html-0s.dtd PUBLIC "-//IETF//DTD HTML 2.0 Strict Level 0//EN" html-0s.dtd -- ISO latin 1 entity set for HTML -- PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML" ISOlat1.sgml 8.4. Character Entity Sets The HTML DTD defines the following entities. They represent particular graphic characters which have special meanings in places in the markup, or may not be part of the character set available to the writer. 8.4.1. Numeric and Special Graphic Entity Set The following table lists each of the characters included from the Numeric and Special Graphic entity set, along with its name, syntax for use, and description. This list is derived from `ISO Standard 8879:1986//ENTITIES Numeric and Special Graphic//EN'. However, HTML does not include for the entire entity set -- only the entities listed below are included. GLYPH NAME SYNTAX DESCRIPTION < lt < Less than sign > gt > Greater than sign & amp & Ampersand " quot " Double quote sign 8.4.2. ISO Latin 1 Character Entity Set The following public text lists each of the characters specified in the Added Latin 1 entity set, along with its name, syntax for use, and description. This list is derived from ISO Standard 8879:1986//ENTITIES Added Latin 1//EN. HTML includes the entire entity set. <!-- (C) International Organization for Standardization 1986 Permission to copy in any form is granted for use with conforming SGML systems and applications as defined in ISO 8879, provided this notice is included in all copies. --> <!-- Character entity set. Typical invocation: <!ENTITY % ISOlat1 PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML"> %ISOlat1; --> <!-- Modified for use in HTML $Id: ISOlat1.sgml,v 1.2 1994年11月30日 23:45:12 connolly Exp $ --> <!ENTITY AElig CDATA "Æ" -- capital AE diphthong (ligature) --> <!ENTITY Aacute CDATA "Á" -- capital A, acute accent --> <!ENTITY Acirc CDATA "Â" -- capital A, circumflex accent --> <!ENTITY Agrave CDATA "À" -- capital A, grave accent --> <!ENTITY Aring CDATA "Å" -- capital A, ring --> <!ENTITY Atilde CDATA "Ã" -- capital A, tilde --> <!ENTITY Auml CDATA "Ä" -- capital A, dieresis or umlaut mark --> <!ENTITY Ccedil CDATA "Ç" -- capital C, cedilla --> <!ENTITY ETH CDATA "Ð" -- capital Eth, Icelandic --> <!ENTITY Eacute CDATA "É" -- capital E, acute accent --> <!ENTITY Ecirc CDATA "Ê" -- capital E, circumflex accent --> <!ENTITY Egrave CDATA "È" -- capital E, grave accent --> <!ENTITY Euml CDATA "Ë" -- capital E, dieresis or umlaut mark --> <!ENTITY Iacute CDATA "Í" -- capital I, acute accent --> <!ENTITY Icirc CDATA "Î" -- capital I, circumflex accent --> <!ENTITY Igrave CDATA "Ì" -- capital I, grave accent --> <!ENTITY Iuml CDATA "Ï" -- capital I, dieresis or umlaut mark --> <!ENTITY Ntilde CDATA "Ñ" -- capital N, tilde --> <!ENTITY Oacute CDATA "Ó" -- capital O, acute accent --> <!ENTITY Ocirc CDATA "Ô" -- capital O, circumflex accent --> <!ENTITY Ograve CDATA "Ò" -- capital O, grave accent --> <!ENTITY Oslash CDATA "Ø" -- capital O, slash --> <!ENTITY Otilde CDATA "Õ" -- capital O, tilde --> <!ENTITY Ouml CDATA "Ö" -- capital O, dieresis or umlaut mark --> <!ENTITY THORN CDATA "Þ" -- capital THORN, Icelandic --> <!ENTITY Uacute CDATA "Ú" -- capital U, acute accent --> <!ENTITY Ucirc CDATA "Û" -- capital U, circumflex accent --> <!ENTITY Ugrave CDATA "Ù" -- capital U, grave accent --> <!ENTITY Uuml CDATA "Ü" -- capital U, dieresis or umlaut mark --> <!ENTITY Yacute CDATA "Ý" -- capital Y, acute accent --> <!ENTITY aacute CDATA "á" -- small a, acute accent --> <!ENTITY acirc CDATA "â" -- small a, circumflex accent --> <!ENTITY aelig CDATA "æ" -- small ae diphthong (ligature) --> <!ENTITY agrave CDATA "à" -- small a, grave accent --> <!ENTITY aring CDATA "å" -- small a, ring --> <!ENTITY atilde CDATA "ã" -- small a, tilde --> <!ENTITY auml CDATA "ä" -- small a, dieresis or umlaut mark --> <!ENTITY ccedil CDATA "ç" -- small c, cedilla --> <!ENTITY eacute CDATA "é" -- small e, acute accent --> <!ENTITY ecirc CDATA "ê" -- small e, circumflex accent --> <!ENTITY egrave CDATA "è" -- small e, grave accent --> <!ENTITY eth CDATA "ð" -- small eth, Icelandic --> <!ENTITY euml CDATA "ë" -- small e, dieresis or umlaut mark --> <!ENTITY iacute CDATA "í" -- small i, acute accent --> <!ENTITY icirc CDATA "î" -- small i, circumflex accent --> <!ENTITY igrave CDATA "ì" -- small i, grave accent --> <!ENTITY iuml CDATA "ï" -- small i, dieresis or umlaut mark --> <!ENTITY ntilde CDATA "ñ" -- small n, tilde --> <!ENTITY oacute CDATA "ó" -- small o, acute accent --> <!ENTITY ocirc CDATA "ô" -- small o, circumflex accent --> <!ENTITY ograve CDATA "ò" -- small o, grave accent --> <!ENTITY oslash CDATA "ø" -- small o, slash --> <!ENTITY otilde CDATA "õ" -- small o, tilde --> <!ENTITY ouml CDATA "ö" -- small o, dieresis or umlaut mark --> <!ENTITY szlig CDATA "ß" -- small sharp s, German (sz ligature) --> <!ENTITY thorn CDATA "þ" -- small thorn, Icelandic --> <!ENTITY uacute CDATA "ú" -- small u, acute accent --> <!ENTITY ucirc CDATA "û" -- small u, circumflex accent --> <!ENTITY ugrave CDATA "ù" -- small u, grave accent --> <!ENTITY uuml CDATA "ü" -- small u, dieresis or umlaut mark --> <!ENTITY yacute CDATA "ý" -- small y, acute accent --> <!ENTITY yuml CDATA "ÿ" -- small y, dieresis or umlaut mark --> 9. Glossary absolute URI a URI in absolute form, as per [URL] anchor a hyperlink navigation option; typically, a highlighted phrase marked as an <A> element. base URI URI used as the base of an HTML document for the purpose of resolving hyperlink destinations. character An atom of information, for example a letter or a digit. Graphic characters have associated glyphs, where as control characters have associated processing semantics. character encoding scheme A function whose domain is the set of sequences of octets, and whose range is the set of sequences of characters from a character repertoire; that is, a sequence of octets and a character encoding scheme determines a sequence of characters. character repertoire A finite set of characters; e.g. the range of a coded character set. code position An integer. A coded character set and a code position from its domain determine a character. coded character set A function whose domain is a subset of the integers and whose range is a character repertoire. That is, for some set of integers (usually of the form {0, 1, 2, ..., N} ), a coded character set and an integer in that set determine a character. Conversely, a character and a coded character set determine the character's code position (or, in rare cases, a few code positions). conforming HTML user agent A user agent that conforms to this specification in its processing of the Internet Media Type `text/html; version=2.0'. data character Characters other than markup, which make up the content of elements. document character set a coded character set whose range includes all characters used in a document. Every SGML document has exactly one document character set. Numeric character references are resolved via the document character set. DTD document type definition. Rules that apply SGML to the markup of documents of a particular type, including a set of element and entity declarations. [SGML] element A component of the hierarchical structure defined by a document type definition; it is identified in a document instance by descriptive markup, sually a start-tag and end-tag. [SGML] end-tag Descriptive markup that identifies the end of an element. [SGML] entity data with an associated notation or interpretation; for example, a sequence of octets associated with an Internet Media Type.[SGML] fragment identifier the portion of an HREF attribute value following the `#' character which modifies the prenentation of the destination of a hyperlink. form data set a sequence of name/value pairs; the names are given by an HTML document and the values are given by a user. HTML document An SGML document conforming to this document type definition. hyperlink a relationship between to resources, called the source and the destination. markup Syntactically delimited characters added to the data of a document to represent its structure. There are four different kinds of markup: descriptive markup (tags), references, markup declarations, and processing instructions.[SGML] may A document or user interface is conforming whether this statement applies or not. media type an Internet Media Type, as per [IMEDIA]. message entity a head and body. The head is a collection of name/value fields, and the body is a sequence of octets. The head defines the content type and content transfer encoding of the body. [MIME] minimally conforming HTML user agent A user agent that conforms to this specification except for form processing. It may only process level 1 HTML documents. must Documents or user agents in conflict with this statement are not conforming. SGML document A sequence of characters organized physically as a set of entities and logically into a hierarchy of elements. An SGML document consists of data characters and markup; the markup describes the structure of the information and an instance of that structure.[SGML] shall If a document or user agent conflicts with this statement, it does not conform to this specification. should If a document or user agent conflicts with this statement, undesirable results may occur in practice even though it conforms to this specification. start-tag Descriptive markup that identifies the start of an element and specifies its generic identifier and attributes. [SGML] syntax-reference character set A coded character set whose range includes all characters used for markup; e.g. name characters and delimiter characters. tag Markup that delimits an element. A tag includes a name which refers to an element declaration in the DTD, and may include attributes.[SGML] text entity A finite sequence of characters. A text entity typically takes the form of a sequence of octets with some associated character encoding scheme, transmitted over the network or stored in a file.[SGML] typical Typical processing is described for many elements. This is not a mandatory part of the specification but is given as guidance for designers and to help explain the uses for which the elements were intended. URI A Universal Resource Identifier is a formatted string that serves as an identifier for a resource, typcally on the Internet. URIs are used in HTML to identify the destination of hyperlinks. URIs in common practice include Uniform Resource Locators (URLs)[URL] and Relative URLs[RELURL]. user agent A component of a distributed system that presents an interface and processes requests on behalf of a user; for example, a www browser or a mail user agent. WWW The World-Wide Web is a hypertext-based, distributed information system created by researchers at CERN in Switzerland. Users may create, edit or browse hypertext documents. `http://www.w3.org/' 10. Bibliography [URI] T. Berners-Lee. ``Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World- Wide Web.'' RFC 1630, CERN, June 1994. [URL] T. Berners-Lee, L. Masinter, and M. McCahill. ``Uniform Resource Locators (URL).'' RFC 1738, CERN, Xerox PARC, University of Minnesota, October 1994. [HTTP] T. Berners-Lee, R. T. Fielding, and H. Frystyk Nielsen. ``Hypertext Transfer Protocol - HTTP/1.0.'' Work in Progress (draft-ietf-http-v10-spec-00.ps), MIT, UC Irvine, CERN, March 1995. [MIME] N. Borenstein and N. Freed. ``MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies.'' RFC 1521, Bellcore, Innosoft, September 1993. [RELURL] R. T. Fielding. ``Relative Uniform Resource Locators.'' Work in Progress (draft-ietf-uri-relative-url-06.txt), UC Irvine, March 1995. [GOLD90] C. F. Goldfarb. ``The SGML Handbook.'' Y. Rubinsky, Ed., Oxford University Press, 1990. [IMEDIA] J. Postel. ``Media Type Registration Procedure.'' RFC 1590, USC/ISI, March 1994. [IANA] J. Reynolds and J. Postel. ``Assigned Numbers.'' STD 2, RFC 1700, USC/ISI, October 1994. [SQ91] SoftQuad. ``The SGML Primer.'' 3rd ed., SoftQuad Inc., 1991. [US-ASCII] US-ASCII. Coded Character Set - 7-Bit American Standard Code for Information Interchange. Standard ANSI X3.4-1986, ANSI, 1986. [ISO-8859-1] ISO 8859. International Standard -- Information Processing -- 8-bit Single-Byte Coded Graphic Character Sets -- Part 1: Latin Alphabet No. 1, ISO 8859-1:1987. Part 2: Latin alphabet No. 2, ISO 8859-2, 1987. Part 3: Latin alphabet No. 3, ISO 8859-3, 1988. Part 4: Latin alphabet No. 4, ISO 8859-4, 1988. Part 5: Latin/Cyrillic alphabet, ISO 8859-5, 1988. Part 6: Latin/Arabic alphabet, ISO 8859-6, 1987. Part 7: Latin/Greek alphabet, ISO 8859-7, 1987. Part 8: Latin/Hebrew alphabet, ISO 8859-8, 1988. Part 9: Latin alphabet No. 5, ISO 8859-9, 1990. [SGML] ISO 8879. Information Processing - Text and Office Systems - Standard Generalized Markup Language (SGML), 1986. 11. Appendices These appendices are provided for informational reasons only - they do not form a part of the HTML specification. 11.1. The ANSI/ISO 8859-1 Coded Character Set This list, sorted numerically, is derived from ANSI/ISO 8859-1 8-bit single-byte coded graphic character set: REFERENCE DESCRIPTION � -  Unused 	 Horizontal tab Line feed  -  Unused   Space ! Exclamation mark " Quotation mark # Number sign $ Dollar sign % Percent sign & Ampersand ' Apostrophe ( Left parenthesis ) Right parenthesis * Asterisk + Plus sign , Comma - Hyphen . Period (fullstop) / Solidus (slash) 0 - 9 Digits 0-9 : Colon ; Semi-colon < Less than = Equals sign > Greater than ? Question mark @ Commercial at A - Z Letters A-Z [ Left square bracket \ Reverse solidus (backslash) ] Right square bracket ^ Caret _ Horizontal bar (underscore) ` Acute accent a - z Letters a-z { Left curly brace | Vertical bar } Right curly brace ~ Tilde  -   Unused ¡ Inverted exclamation ¢ Cent sign £ Pound sterling ¤ General currency sign ¥ Yen sign ¦ Broken vertical bar § Section sign ¨ Umlaut (dieresis) © Copyright ª Feminine ordinal « Left angle quote, guillemotleft ¬ Not sign ­ Soft hyphen ® Registered trademark ¯ Macron accent ° Degree sign ± Plus or minus ² Superscript two ³ Superscript three ´ Acute accent µ Micro sign ¶ Paragraph sign · Middle dot ¸ Cedilla ¹ Superscript one º Masculine ordinal » Right angle quote, guillemotright ¼ Fraction one-fourth ½ Fraction one-half ¾ Fraction three-fourths ¿ Inverted question mark À Capital A, grave accent Á Capital A, acute accent  Capital A, circumflex accent à Capital A, tilde Ä Capital A, dieresis or umlaut mark Å Capital A, ring Æ Capital AE dipthong (ligature) Ç Capital C, cedilla È Capital E, grave accent É Capital E, acute accent Ê Capital E, circumflex accent Ë Capital E, dieresis or umlaut mark Ì Capital I, grave accent Í Capital I, acute accent Î Capital I, circumflex accent Ï Capital I, dieresis or umlaut mark Ð Capital Eth, Icelandic Ñ Capital N, tilde Ò Capital O, grave accent Ó Capital O, acute accent Ô Capital O, circumflex accent Õ Capital O, tilde Ö Capital O, dieresis or umlaut mark × Multiply sign Ø Capital O, slash Ù Capital U, grave accent Ú Capital U, acute accent Û Capital U, circumflex accent Ü Capital U, dieresis or umlaut mark Ý Capital Y, acute accent Þ Capital THORN, Icelandic ß Small sharp s, German (sz ligature) à Small a, grave accent á Small a, acute accent â Small a, circumflex accent ã Small a, tilde ä Small a, dieresis or umlaut mark å Small a, ring æ Small ae dipthong (ligature) ç Small c, cedilla è Small e, grave accent é Small e, acute accent ê Small e, circumflex accent ë Small e, dieresis or umlaut mark ì Small i, grave accent í Small i, acute accent î Small i, circumflex accent ï Small i, dieresis or umlaut mark ð Small eth, Icelandic ñ Small n, tilde ò Small o, grave accent ó Small o, acute accent ô Small o, circumflex accent õ Small o, tilde ö Small o, dieresis or umlaut mark ÷ Division sign ø Small o, slash ù Small u, grave accent ú Small u, acute accent û Small u, circumflex accent ü Small u, dieresis or umlaut mark ý Small y, acute accent þ Small thorn, Icelandic ÿ Small y, dieresis or umlaut mark 11.2. Obsolete Features This section describes elements that are no longer part of HTML. Client implementors should implement these obsolete elements for compatibility with previous versions of the HTML specification. 11.2.1. Comment Element The Comment element is used to delimit unneeded text and comments. The Comment element has been introduced in some HTML applications but should be replaced by the SGML comment feature in new HTML interpreters (see Section 2.2.5). 11.2.2. Highlighted Phrase Element <HP> The Highlighted Phrase element should be ignored if not implemented. This element has been replaced by more meaningful elements (see Section 8). Example of use: <HP1>first highlighted phrase</HP1>non- highlighted text<HP2>second highlighted phrase</HP2> etc. 11.2.3. Plain Text Element <PLAINTEXT> The Plain Text element is used to terminates the HTML entity and to indicate that what follows is not SGML which does not require parsing. Instead, an old HTTP convention specified that what followed was an ASCII (MIME ``text/plain'') body. Its presence is an optimization. There is no closing tag. Example of use: <PLAINTEXT> 0001 This is line one of a long listing 0002 file from <ANY@HOST.INC.COM> which is sent 11.2.4. Example and Listing Elements <XMP> ... </XMP> and <LISTING> ... </LISTING> The Example and Listing elements have been replaced by the Preformatted Text element (Section 10.2). These styles allow text of fixed-width characters to be embedded absolutely as is into the document. The syntax is: <LISTING> ... </LISTING> or <XMP> ... </XMP> The text between these tags is typically rendered in a monospaced font so that any formatting done by character spacing on successive lines will be maintained. Between the opening and closing tags: * The text may contain any ISO Latin-1 printable characters, except for the end-tag opener. The Example and Listing elements have historically used specifications which do not conform to SGML. Specifically, the text may contain ISO Latin printable characters, including the tag opener, as long it they does not contain the closing tag in full. * SGML does not support this form. HTML interpreters may vary on how they interpret other tags within Example and Listing elements. * Line boundaries within the text are rendered as a move to the beginning of the next line, except for one immediately following a start-tag or immediately preceding an end-tag. * The horizontal tab character must be interpreted as the smallest positive nonzero number of spaces which will leave the number of characters so far on the line as a multiple of 8. Its use is not recommended. The Listing element is rendered so that at least 132 characters fit on a line. The Example element is rendered to that at least 80 characters fit on a line but is otherwise identical to the Listing element. 11.3. Proposed Features This section describes proposed HTML elements and entities that are not currently supported under HTML Levels 1, or 2, but may be supported in the future. 11.3.1. Additional Character Entities To indicate special characters, HTML uses entity or numeric representations. Additional character presentations are proposed: CHARACTER REPRESENTATION Non-breaking space Soft-hyphen ­ Registered ® Copyright © 11.3.2. Defining Instance Element <DFN> ... </DFN> The Defining Instance element indicates the defining instance of a term. The typical rendering is bold or bold italic. This element is not widely supported. 11.3.3. Strike Element <STRIKE> ... </STRIKE> The Strike element is proposed to indicate strikethrough, a font style in which a horizontal line appears through characters. This element is not widely supported. 11.3.4. Underline Element <U> ... </U> The Underline element is proposed to indicate that the text should be rendered as underlined. This proposed tag is not supported by all HTML interpreters. Example of use: The text <U>shown here</U> is rendered in the document as underlined. 12. Acknowledgments The HTML document type was designed by Tim Berners-Lee at CERN as part of the 1990 World Wide Web project. In 1992, Dan Connolly wrote the HTML Document Type Definition (DTD) and a brief HTML specification. Since 1993, a wide variety of Internet participants have contributed to the evolution of HTML, which has included the addition of in-line images introduced by the NCSA Mosaic software for WWW. Dave Raggett played an important role in deriving the FORMS material from the HTML+ specification. Dan Connolly and Karen Olson Muldrow rewrote the HTML Specification in 1994. The document was then edited by the HTML working group as a whole, with updates being made by Eric Schieler, Mike Knezovich, and Eric W. Sink at Spyglass, Inc. Finally, Roy Fielding restructured the entire draft into its current form. Special thanks to the many people who have contributed to this specification: Terry Allen Marc Andreessen Tim Berners-Lee Paul Burchard James Clark Daniel W. Connolly Roy T. Fielding Peter Flynn Jay Glicksman Paul Grosso Eduardo Gutentag Bill Hefley Chung-Jen Ho Mike Knezovich Tom Magliery Murray Maloney Larry Masinter Karen Olson Muldrow Bill Perry Dave Raggett E. Corprew Reed Yuri Rubinsky Eric Schieler James L. Seidman Eric W. Sink Stuart Weibel Chris Wilson Francois Yergeau 12.1. Authors' Addresses Tim Berners-Lee Director, W3 Consortium MIT Laboratory for Computer Science 545 Technology Square Cambridge, MA 02139, U.S.A. Tel: +1 (617) 253 9670 Fax: +1 (617) 258 8682 Email: timbl@w3.org Daniel W. Connolly Research Technical Staff, W3 Consortium MIT Laboratory for Computer Science 545 Technology Square Cambridge, MA 02139, U.S.A. Fax: +1 (617) 258 8682 Email: connolly@w3.org URI: http://www.w3.org/hypertext/WWW/People/Connolly/