rfc1866.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                    T. Berners-Lee
Request for Comments: 1866                                      MIT/W3C
Category: Standards Track                                   D. Connolly
                                                          November 1995


                    Hypertext Markup Language - 2.0

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

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" Internet Media Type (RFC 1590) and MIME Content Type
   (RFC 1521) is defined by this specification.

Table of Contents

    1.     Introduction ........................................... 2
    1.1    Scope .................................................. 3
    1.2    Conformance ............................................ 3
    2.     Terms .................................................. 6
    3.     HTML as an Application of SGML .........................10
    3.1    SGML Documents .........................................10
    3.2    HTML Lexical Syntax ................................... 12
    3.3    HTML Public Text Identifiers .......................... 17
    3.4    Example HTML Document ................................. 17
    4.     HTML as an Internet Media Type ........................ 18



Berners-Lee & Connolly      Standards Track                     [Page 1]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


    4.1    text/html media type .................................. 18
    4.2    HTML Document Representation .......................... 19
    5.     Document Structure .................................... 20
    5.1    Document Element: HTML ................................ 21
    5.2    Head: HEAD ............................................ 21
    5.3    Body: BODY ............................................ 24
    5.4    Headings: H1 ... H6 ................................... 24
    5.5    Block Structuring Elements ............................ 25
    5.6    List Elements ......................................... 28
    5.7    Phrase Markup ......................................... 30
    5.8    Line Break: BR ........................................ 34
    5.9    Horizontal Rule: HR ................................... 34
    5.10   Image: IMG ............................................ 34
    6.     Characters, Words, and Paragraphs ..................... 35
    6.1    The HTML Document Character Set ....................... 36
    7.     Hyperlinks ............................................ 36
    7.1    Accessing Resources ................................... 37
    7.2    Activation of Hyperlinks .............................. 38
    7.3    Simultaneous Presentation of Image Resources .......... 38
    7.4    Fragment Identifiers .................................. 38
    7.5    Queries and Indexes ................................... 39
    7.6    Image Maps ............................................ 39
    8.     Forms ................................................. 40
    8.1    Form Elements ......................................... 40
    8.2    Form Submission ....................................... 45
    9.     HTML Public Text ...................................... 49
    9.1    HTML DTD .............................................. 49
    9.2    Strict HTML DTD ....................................... 61
    9.3    Level 1 HTML DTD ...................................... 62
    9.4    Strict Level 1 HTML DTD ............................... 63
    9.5    SGML Declaration for HTML ............................. 64
    9.6    Sample SGML Open Entity Catalog for HTML .............. 65
    9.7    Character Entity Sets ................................. 66
    10.    Security Considerations ............................... 69
    11.    References ............................................ 69
    12.    Acknowledgments ....................................... 71
    12.1   Authors' Addresses .................................... 71
    13.    The HTML Coded Character Set .......................... 72
    14.    Proposed Entities ..................................... 75

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.




Berners-Lee & Connolly      Standards Track                     [Page 2]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


   As HTML is an application of SGML, this specification assumes a
   working knowledge of [SGML].

1.1. Scope

   HTML has been in use by the World-Wide Web (WWW) global information
   initiative since 1990. Previously, informal documentation on HTML has
   been available from a number of sources on the Internet. This
   specification brings together, clarifies, and formalizes a set of
   features that roughly corresponds to the capabilities of HTML in
   common use prior to June 1994. A number of new features to HTML are
   being proposed and experimented in the Internet community.

   This document thus defines a HTML 2.0 (to distinguish it from the
   previous informal specifications). Future (generally upwardly
   compatible) versions of HTML with new features will be released with
   higher version numbers.

   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'. 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 aspects
   of the behavior of HTML user agents.

1.2.1. Documents

   A document is a conforming HTML document if:

        * It is a conforming SGML document, and it conforms to the
        HTML DTD (see 9.1, "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 identified in notes like this throughout
            this specification.

        * It conforms to the application conventions in this
        specification. For example, the value of the HREF attribute



Berners-Lee & Connolly      Standards Track                     [Page 3]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


        of the <A> element must conform to the URI syntax.

        * Its document character set includes [ISO-8859-1] and
        agrees with [ISO-10646]; that is, each code position listed
        in 13, "The HTML Coded Character Set" is included, and each
        code position in the document character set is mapped to the
        same character as [ISO-10646] 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
            [ISO-10646] repertoire. The critical distinction is
            that numeric character references agree with
            [ISO-10646] regardless of how the document is
            encoded.

1.2.2. Feature Test Entities

   The HTML DTD defines a standard HTML document type and several
   variations, by way of feature test entities. Feature test entities
   are declarations in the HTML DTD that control the inclusion or
   exclusion of portions of the DTD.

    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 selects a more prescriptive document
            type definition that eliminates those features. It is
            set to `IGNORE' by default.

            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 allows these features. It is set to `INCLUDE' by
            default.



Berners-Lee & Connolly      Standards Track                     [Page 4]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


            Documents generated by translation software or editing
            software should not contain deprecated idioms.

1.2.3. 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 4.2.1, "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 6.1, "The HTML Document Character Set".

            NOTE - To support non-western writing systems, HTML
            user agents are encouraged to support
            `ISO-10646-UCS-2' or similar character encoding
            schemes and as much of the character repertoire of
            [ISO-10646] 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
        behavior of conforming user agents.

        * It allows the user to traverse (or at least attempt to
        traverse, resources permitting) all hyperlinks from <A>
        elements in an HTML document.

   An HTML user agent is a level 2 user agent if, additionally:

        * 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.









Berners-Lee & Connolly      Standards Track                     [Page 5]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


2. Terms

    absolute URI
            a URI in absolute form; for example, as per [URL]

    anchor
            one of two ends of a hyperlink; typically, a phrase
            marked as an <A> element.

    base URI
            an absolute URI used in combination with a relative URI
            to determine another absolute URI.

    character
            An atom of information, for example a letter or a digit.
            Graphic characters have associated glyphs, whereas
            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'.




Berners-Lee & Connolly      Standards Track                     [Page 6]

RFC 1866            Hypertext Markup Language - 2.0        November 1995


    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, usually 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 `#'