2005/pre-id/draft-raggett-www-html-00.txt

HTML+ Document Format                                       Dave Raggett
Internet Draft                                           Hewlett Packard
                                                       28th October 1993


                    HTML+  (Hypertext markup format)

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.
Internet-Drafts may be updated, replaced, or obsoleted by other
documents at any time. It is not appropriate to use Internet-Drafts as
reference material or to cite them other than as a "working draft" or
"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 ds.internic.txt, nic.nordu.net, ftp.nisc.sri.com or
munnari.oz.au.

Distribution  of this document is unlimited. Please mail comments to the
author at dsr@hplb.hpl.hp.com or to the discussion list:
www-talk@nxoc01.cern.ch

This  draft is valid until May 1st, 1994. It is available in the file
draft-raggett-www-html-00.ps and draft-raggett-www-html-00.txt in the
internet-drafts directories on the hosts mentioned above. Readers are
recommended to try and obtain the Postscript version, which contains
figures and formattting examples which are missing from the plain text
version.

Abstract 

This  draft presents a proposal for a light weight delivery format for
browsing and querying information in a web of globally distributed
hypertext, accessible over the Internet. HTML+ embodies a pageless
model making it suitable for efficient rendering on a wide range of
display types, for example, VT100 terminals, X11 Workstations, Windows
3.x and the Macintosh. HTML+ is based upon SGML, and represents
document elements at a logical level, e.g. headers, paragraphs, lists,
tables, and figures. Authors can choose to create HTML+ documents
directly, or to use filters to convert from other formats such as
LaTeX, Framemaker, and Word for Windows.

HTML+  has grown out of several years experience with the HTML document
format in the World Wide Web community. Browser writers are
experimenting with extensions to HTML and it is now appropriate to draw
these ideas together into a revised document format.. The new format is
designed to allow a gradual roll over from HTML, adding features like


Internet Draft                     1                       November 1993
HTML+ Document Format                                            Raggett


tables, captioned figures and fill-out forms for querying remote
databases or mailing questionnaires.  Large documents can be split into
a number of smaller nodes for reduced latency, with explicit or
implicit navigation links. This draft also includes a proposal to add
direct support for mathematical formulae. Authors can include limited
presentation hints, and further control may  eventually be possible via
associated style sheets.

                           Table  of Contents

    HTML+ Discussion Document 4
        Introduction 4
        Positioning of HTML+ 4
        HTML+ and HTML 5
        HTML+ and SGML 5

    An Overview of HTML+ 6
        Document Structure 6
        Large Documents 7

    Headers 7

    Paragraphs and <P> 8

    Normal Text 9
        Character Sets and Entity Definitions 10
        Hypertext Links 11
        Character Emphasis 13
        Presentation Only Tags 13
        Generic Emphasis 13
        Logical Emphasis 14
        Extending the Set of Logical Roles 15
        Annotations 15
        Images 15
        Change Bars and Document Amendments 17
        Conditional Text 18
        Explicit Line Breaks 18

    Different Paragraph Styles 19
        Longer Quotations 19
        Abstracts 19
        Bylines 19
        Notes and admonishments 20

    Lists 20
        Ordered Lists 21
        Bulleted Lists 21
        Plain Lists 22
        Definition Lists 23

    Figures 24


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        Active Areas 25
        Placing Hypertext Buttons on Images 25
        Possible extensions 26

    Tables 26
        Implementation Issues for Tables 28

    Fill-out Forms and Input fields 28
        Sending form data to an HTTP server 33
        Sending a form via Electronic Mail 34

    Literal and Preformatted Text 34

    Mathematical Equations 36

    Indexing 39

    Document declarations 40
        HTMLPLUS 40
        The HEAD and BODY elements 40
        TITLE 40
        ISINDEX 40
        NEXTID 41
        BASE 41
        LINK 41

    Dealing with Large Documents 43

    Acknowledgements 45

    References 45

    Appendix I - The HTML+ DTD 46

    Appendix II - Character Entity Names 57

    Appendix III - Code for Polygon testing 58

    Appendix IV - Sorted list of tags and attributes 60


Internet Draft                     3                       November 1993
HTML+ Document Format                                            Raggett


                        HTML+ (Hypertext markup format)

1  HTML+ Discussion Document

Following  the WWW workshop in July 1993 and subsequent discussions on
www-talk, it seems an opportune moment to try and reach a consensus
before writing a more formal draft as an informational RFC. 

1.1  Introduction

The  World Wide Web is a wide-area client-server architecture for
retrieving hypermedia documents over the Internet. It also supports a
means of searching remote information sources, for example
bibliographies, phone directories and instruction manuals. There are
three main ingredients: naming schemes for retrievable objects,
protocols and interchange formats.

    o   Universal naming scheme for documents. The Universal Resource
        Location (URL) syntax specifies documents in terms of the
        protocol to be used to retrieve them, their  Internet Host and
        path name. A format for location independent lifetime
        identifiers is currently being defined by a working group of
        the IETF. A network protocol will allow Universal Resource
        Numbers (URNs) to be resolved to the URL for the nearest
        available copy. A URN may specify a number of variants of a
        document, but the URL will  always specify a single copy.

    o   Use of de facto protocols for retrieving documents over the
        Internet including FTP, NNTP, WAIS, Gopher and HTTP. The
        latter being designed specifically for the World Wide Web,
        and uses the MIME message format for document exchange.

    o   A document format supporting hypertext links based on URLs and
        URNs which can  be rendered on a wide variety of display types.
        HTML+ is intended in this role as a  successor to the existing
        HTML format.

HTML+  documents offer a means for providing hypertext links to a
variety of media including images, sound sequences, MPEG movies,
Postscript files and other formats. These links allow a global web of
information sources to be established as new servers and document names
are announced. Registers of information sources can also be made
available via the web, using its ability to let users search for
information via keywords. It is hoped that HTML+ will be useful for
information exchange via email and network news as well as HTTP.

1.2  Positioning of HTML+

HTML+  is designed for use in the World Wide Web as a non-proprietary
delivery format for wide-area hypertext. It embodies a pageless model
making it suitable for efficient rendering on a wide range of display


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HTML+ Document Format                                            Raggett


types including VT100 terminals, X11, Windows 3.1 and the Macin- tosh.
HTML+ is based upon SGML and represents document elements at a logical
level. Authors may choose to create HTML+ documents directly or to use
filters to convert from other formats such as LaTeX, Framemaker, and
Word for Windows.

1.3  HTML+ and HTML

HTML+  is a superset of HTML and designed to allow a gradual roll over
from the earlier format, with features like tables, captioned figures
and fill-out forms for querying remote data- bases or mailing
questionnaires. Large documents can be split into a number of smaller
nodes for reduced latency, with explicit or implicit navigation links.
This draft also includes a proposal to add support for mathematical
formulae. Authors can include limited presentation hints, and further
control may eventually be possible via associated style sheets.

1.4  HTML+ and SGML

HTML+  is based on the Standard Generalized Markup Language which is an
international standard for document markup that is becoming
increasingly important. The term markup derives from the way
proof-readers have traditionally pencilled in marks that indicate how a
document is to be revised.

SGML  grew out of a decade of work addressing the need for capturing the
logical elements of documents as opposed to the processing functions to
be performed on those elements. SGML is essentially an extensible
document description language, based on a notation for embedding tags
into the body of a document' s text. It is defined by the international
standard ISO 8879.  The markup structure permitted for each class of
documents is defined by an SGML Document Type Definition, usually
abbreviated to DTD.

A  lot of work is underway to produce DTDs for a range of purposes.
These include ISO 12083 for books and ISO 10744 which defines the
HyTime architectural forms for hypermedia/time- based documents. The
Text Encoding Initiative (TEI) is an international research project for
SGML-based document exchange in the humanities. Publishers are
cooperating to produce  common DTDs for computer manuals, e.g. the
DocBook DTD. The CALS programme of the US Department of Defence defines
SGML DTDs for documentation for defence procurement contracts.

So  what sets HTML+ apart from these efforts? It is impractical to
design a DTD to meet the needs of all possible users. Instead, the
markup has to be tailored to the needs of a specific community. HTML+
is aimed at fulfilling the dream of a web of information freely
accessible over the Internet with links between documents spanning
continents. The need to support a very wide range of display types and
to keep browser software as simple as possible limits the complexity
that can be handled. Similarly the disparate needs of authors has led


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HTML+ Document Format                                            Raggett


to the inclu- sion of limited rendering hints. The features supported
arise from several years experience with the World Web and the existing
HTML format.

2  An Overview of HTML+

HTML+  documents consists of headers, paragraphs, lists, tables and
figures. A simple example of an HTML+ document is:

    <title>A simple HTML+ Document</title>

    <h1 id="a1">This is a level one header</h1>

    <p>This is some normal text which will wrap at the window margin.
    You can emphasise <em>parts of the text</em> if you wish.

    <p>This is a new paragraph. Note that unlike title and header tags
    the matching end tag is not needed.

The  text of the document includes tags which are enclosed in <angle
brackets>. Many tags require matching end tags for which the tag name
is preceded by the "/" character. The tags are used to markup the
document's logical elements, for example the title, headers and
paragraphs. Tags may also be accompanied by attributes, e.g. the id
attribute in the header tag which can be used to name destinations for
hypertext links. 

Unlike  most document formats, HTML+ leaves out the processing
instructions that determine the precise appearance, for instance the
font names and point size, the margins, tab settings and how much white
space to leave before and after different elements. The rendering
software makes these choices for itself (perhaps guided by user
preferences). This ensures that browsers can avoid problems with
different page sizes or missing fonts. Logical markup also preserves
essential distinctions that are often lost by lower level procedural
formats, making it easier to carry out operations like indexing and
conversion into other document formats.

Note  that the tag and attribute names are case insensitive. HTML+
parsers are expected to ignore unrecognised tags and attributes, and to
process their contents as if the start/end tags weren't present. SGML
minimisation is not supported - this avoids any possibility of
confusion with unrecognised tags.

2.1  Document Structure

An  HTML+ document consists of some optional declarations followed by
one or more elements from the following:

    o   Headers


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HTML+ Document Format                                            Raggett


    o   Paragraphs

    o   Lists

    o   Figures

    o   Tables

    o   Forms

    o   Literal or Preformatted text

    o   Mathematical formulae

2.2  Large Documents

Keeping  a large document such as a book in one node will increase the
time it takes to retrieve the node over the network. It is generally
better to split large documents into a number of smaller nodes. Many
documents are written with the expectation that the reader will start
at the beginning and read through until the end. If the document is
split into a number of nodes, the intended sequence is known as a path.
HTML+ provides a means for authors to specify such paths either
explicitly via declarations at the beginning of the node or implicitly
according to the context in which a given node is reached. Another
possibility is for servers to send such information independently, e.g.
as MIME message headers.

You  can provide navigation links for readers which appear as buttons on
a toolbar or as entries in a navigation menu. For works using a lot of
technical terms or perhaps in an unfamiliar language, you can provide
glossaries offering further explanation. Readers can invoke this by
double clicking on words, or by drag selection and clicking the
Glossary menu item. You can also provide a search field that is always
present (and can't be scrolled away), in which readers can enter one or
more keywords to search an index. These facilities can be specified
explicitly using the LINK element. Implicit links allow you to define
the table of contents (toc) as an HTML+ document without needing to
place links to the toc in every subdocument. The link back to the toc
is implied when you follow hypertext link from the toc to its
subdocuments.

3  Headers

The  tags H1, H2, ... H6 are used to represent headers. H1 is the most
significant and rendered in a large font (preferably centered). H2 to
H6 are progressively less significant and usually rendered flush left
in smaller fonts. A common convention is to begin the body of a
document with an H1 header, e.g. 

    <h1>Introduction to HTML+</h1>


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HTML+ Document Format                                            Raggett


Header  names should be appropriate to the following section of the
document, while the title should cover the document as a whole. There
are no restrictions on the sequence of headers, e.g. you could use a
level three header following a level one header.Header and section
elements can take an identifier, unique to the current document, for
use as named destinations of  hypertext links. This is specified with
the ID attribute, e.g.

    <h1 id="intro">Introduction to HTML+</h1>

This  allows authors to create hypertext links to particular sections of
documents. It is a good idea to use something obvious when creating an
identifier, to help jog your memory at a later date. WYSIWYG editors
should automatically generate identifiers. In this case, they should
provide a point and click mechanism for defining links so that authors
don't need to deal explicitly with identifier names. Automatic
generation of IDs for headers, paragraphs and other major elements is
important as it makes it easier for other people to create links to
your document, by ensuring that there are plenty of ID attributes
present as potential destinations.

Should  we support headers for which the level is implicitly defined by
nestable section elements? We could also support autonumbering of
headers. Unfortunately, on further investigation these ideas proved
trickier than thought at first, and so have been dropped from this
draft.

4  Paragraphs and <P>

Normal  text is automatically wrapped by the browser at the current
window margin and adapts to changes in window size. The text is
generally shown in a proportional font:

    <P ID="p1">The P element acts as container for the text between
    the start tag &lt;P&gt; and end tag &lt;/P&gt;. You don't need
    to give the end tag as it is implied by the context, e.g. the
    following &lt;P&gt; tag.
    <P ID="p2">If you wish, you may think of the &lt;P&gt; tag as
    a paragraph separator. This works since HTML+ formally doesn't
    require you to wrap text up as paragraphs.

This  would be rendered as:

    The P element acts as a container for the text between the start
    tag <P> and the end  tag </P>. You don't need to give the end
    tag as it is implied by the context, e.g. the  following <P> tag.

    If you wish, you may think of the <P> tag as a paragraph separator.
    This works since HTML+ formally doesn't require you to wrap text up
    as paragraphs.


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HTML+ Document Format                                            Raggett


The  following samples of HTML+ all produce exactly the same results
when displayed:

    <H1>Different ways of using the P element</H1>
    <P>The first piece of text</P><P>The second piece</P>

    <H1>Different ways of using the P element</H1>
    <P>The first piece of text<P>The second piece

    <H1>Different ways of using the P element</H1>
    The first piece of text<P>The second piece

    They all produce:

    Different ways of using the P element

    The first piece of text

    The second piece

In  some situations you will want to preserve the original line breaks
and spacing, for this you should use the LIT or PRE elements, these are
described in a later section. You can force line breaks in normal
paragraph text with the <BR> element, but the browser may wrap lines
arbitrarily at window margins prior to reaching the <BR> element.

The  ALIGN attribute can be used to center a paragraph, e.g. <P
ALIGN=center>. Other possibilities are ALIGN=left (the default),
ALIGN=right, ALIGN=justify and ALIGN=indent. This attribute is a hint
and may be ignored by some browsers. Note that when using explicit line
breaks (see section 5.12) you may wish to switch off word wrap with
WRAP=OFF.

Browsers,  when parsing paragraphs, can choose to simply treat the <P>
tag as denoting a paragraph break. If the paragraph style includes a
blank line between paragraphs, then additional care is needed after
headers and other major elements to avoid inserting an unwanted blank
line, e.g. when a <P> tag directly follows a header. This ability to
perceive <P> as a paragraph  break provides for continuity with HTML,
and allows authors to graduate to treating it as a container in their
own time.

5  Normal Text

Paragraphs  can include the following:

    o   Character entity names for unusual characters such as o which
        are included using  SGML entity definitions: &name; as in
        "the dream of &oacute;engus" which is displayed as: "the dream
        of oengus". The full list of standard entity names recognised


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HTML+ Document Format                                            Raggett


        by  most browsers is given in Appendix II

    o   Character emphasis using logical and presentational markup. The
        set of logical character emphasis can be extended, and HTML+
        provides the means for browsers to deter- mine how to render
        such extensions

    o   Simple footnotes or margin notes, which can be rendered as
        pop-up overlays

    o   Images which act as single characters and which can be
        vertically aligned relative to  the text line in which
        they are embedded

    o   Hypertext Links based on the URL or URN notations

    o   Markup signifying the start and end of change bars. You can
        also mark text as being  removed or added, as is common in
        legal documents 

    o   Conditional text which appears only on-line or only when printed

    o   Input fields when the paragraph is part of a form

    o   Explicit line breaks

5.1  Character Sets and Entity Definitions

By  default, HTML+ documents are made up of 8-bit characters from the
ISO 8859 Latin-1 character set. The network protocol used to retrieve
documents may translate the character set into a locally acceptable
form, e.g. EBCDIC. The HTTP protocol uses the MIME standard (RFC 1341)
to specify the document type and character set. ISO SGML entity
definitions are used to include characters which are missing from the
character set or which would otherwise  be confused with markup
elements, e.g:

        &amp;   ampersand &
        &lt;    less than sign <
        &gt;    greater than sign >
        &quot;  the double quote sign "

Appendix  II lists a broad range of characters and symbols, relating
their ISO names to the corresponding character codes in common
character sets. They allow authors to include accented characters in
7-bit ASCII documents. Some other useful entity definitions are:

        &ndash; en dash (half the width of an em unit)
        &mdash; em dash (equal to width of an "m" character)
        &ensp;  en space
        &emsp;  em space


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HTML+ Document Format                                            Raggett


        &nbsp;  non breaking space
        &shy;   soft hyphen (normally invisible)
        &copy;  copyright sign 
        &trade; trade mark sign 
        &reg;   registered sign 

There  are a large number of entities defined by the ISO, covering most
languages and symbols for publishing and mathematics. Requiring all
browsers to support these would be impractical, e.g. how should a dumb
terminal show such symbols. In some cases there will be accepted ways
of mapping them to normal characters, e.g. as ae and e as e. Perhaps
the safest recommendation is that where authors need to use a
specialised character or symbol, they should use ISO entity names
rather than inventing their own. Browsers should leave unrecognised
entity names untranslated.

In  some cases it is useful to specify the language used in a given
element, with the LANG attribute. The ISO defines abbreviations for
most languages, e.g. FR for french as in: <Q LANG="FR">Je
m'aveugle.</Q>. This attribute permits language dependent layout and
hyphenation decisions, e.g. Hebrew uses right to left word order.

To  allow SGML parsers to recognise entity names, authors should declare
them before use, for example:

 <!ENTITY % ISOcyr1 PUBLIC "ISO 8879-1986//ENTITIES Russian Cyrillic/EN">
 %ISOcyr1;

This  introduces ISOcyr1 as a local name for the ISO public identifier
for the cyrillic alphabet and then includes the associated set of
entity definitions as part of the current document. This declaration is
unnecessary for entities defined within the HTML+ DTD.

5.2  Hypertext Links

HTML+  allows authors to embed hypertext links into the document text.
In a browser this might look to the reader like:

Links  are defined with the A tag[1]. HTML+ supports a number of different 
link types[2].

Clicking  on a link will normally cause the browser to retrieve the
linked document and display it in place of the current one. This
example is represented by the following piece of HTML+

    Links are defined with the <a href="#z1">A tag</a>. HTML+ supports
    a number of <a href="links.html">different link types</a>.

The  first link is to an anchor named "z1" in the current document
(using an ID attribute on some element). The second is to a file named
"links.html" in the same directory as the current document. The link


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HTML+ Document Format                                            Raggett


caption is the text between the start and end tags. The HREF attribute
defines the link destination using the URL or URN notations. This may
be abbreviated in certain circumstances using relative URLs. The link
should be rendered in a clearly distinguishable way, e.g. as a raised
button, or with underlined text in a particular color or emphasis. For
displays without pointing devices, it is suggested that the link is
indicated with a reference number in square brackets after the caption,
which the reader enters to follow the link. Note  that it is illegal
for anchors to include headers, paragraphs, lists etc. The anchor text
is restricted to normal text with emphasis and inline images.

The  A element has several optional attributes:

    ID      This can be used to define a unique identifier for the text
            contained by the A  element. Another document can then make
            a reference to this by putting the identifier after the URL
            for this document, separated by a hash sign. The ID
            attribute replaces the NAME attribute in HTML.

    HREF    This specifies a URL or URN of a linked document which will
            be retrieved when the user clicks on the anchor's label.
            HREF=#id can be used for links to  other parts of the same
            document.

    REL     The relationship the linked document has to this one.
            REL=Subdocument is  used to break long documents into
            smaller ones. This importance of this particular
            attribute value is explained in section 14.

    REV     The reverse relationship type, and the inverse of REL.

    EFFECT  This determines how the browser displays the linked document
            when following the link. EFFECT=Replace causes the browser
            to replace the current document  with the linked one;
            EFFECT=NEW results in the linked document being shown in a
            new window (if practical); and EFFECT=OVERLAY causes the
            linked document to be shown in a pop-up window, as used by
            the Microsoft Windows Help system.

    PRINT   This attribute makes it easy for users to print off the
            current document and relevant parts. PRINT=REFERENCE (the
            default) treats the link as a reference, i.e. the URL is
            given as a footnote; PRINT=FOOTNOTE prints the linked
            document as a footnote; PRINT=SIDEBAR prints the linked
            document as a sidebar; and PRINT=SECTION prints the
            linked document as a follow on section. Use PRINT=SILENT
            when you don't want the link referenced or printed out.

    TITLE   Defines the title to use when the linked document is
            otherwise untitled.


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HTML+ Document Format                                            Raggett


    TYPE    The MIME content type of the linked document - for use
            in providing presentation cues only, as it could easily
            become out of date.

    SIZE    The size in bytes for the linked document. This should only
            be used as a guide  to progress in retrieving documents, as
            it is likely to get out of step with  changes to the target
            document.

    METHODS This is a comma separated list of HTTP methods supported
            by the linked  object. The browser might choose a different
            way of rendering the link for say  searchable objects.

    SHAPE   This is used to define shaped buttons on top of images or
            figures, and is explained later on.

You  can also use the LINK element at the start of the document to
define document-wide relationships with other documents, e.g. a link to
a table of contents. This is described later on.

5.3  Character Emphasis

There  has been considerable discussion on how to represent character
emphasis. The previous draft of HTML+ used a single element to handle
all forms with a role attribute for the logical role, and other
attributes for providing hints as to how to render the emphasis. This
mechanism was seen as being overloaded and prompted the use of separate
elements in the current draft.

5.4  Presentation Only Tags

In  many cases it is convenient to indicate directly how the text is to
be rendered, e.g. as italic, bold, underline or strike-through:

    <I>italic text</I>      italic text
    <B>bold text</B>        bold text
    <U>underlined text</U>  underlined text
    <S>strike through</S>   strike through
    <SUP>superscript</SUP>  superscript
    <SUB>subscript</SUB>    subscript
    <TT>fixed pitch</TT>    fixed pitch (TT for Teletype)

These  tags may be nested to combine effects, e.g.
bold-italic-fixed-pitch text, and should be considered as hints rather
than as binding obligations on the browser, e.g.

    Some <B><I><TT>bold italic fixed pitch text</TT></I></B>.

which  is rendered as: Some bold italic fixed pitch text.

5.5  Generic Emphasis


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HTML+ Document Format                                            Raggett


These  are some tags for indicating a level of emphasis without
committing oneself to how they should be rendered:

    <EM>normal emphasis</EM>        typically italic
    <STRONG>strong emphasis</STRONG>        typically bold

5.6  Logical Emphasis

These  tags indicate the role of the marked text, e.g. bibliographic
references. By using a stand- ard way of marking up text, it becomes
possible to automatically index such references. There are a
potentially huge number of different distinctions that could be made,
and the set given below is intentionally minimalistic. Discussion is
welcomed on just which elements should be included in HTML+ given its
intended role as a delivery format for hypertext documents:

    q       a short quotation which can be included inline,
            e.g. <q>to be or not to be, that is the question</q>
            use <q> and </q> in place of double quote marks.

    cite    citation, e.g. <cite>Festinger, L.(1957), <I>A Theory
            of Cognitive Dissonance</I>, Stanford.</cite>

    person  proper names, e.g. <person>Albert Einstein</person>

    acronym acronyms e.g <acronym>NATO</acronym>

    abbrev  abbreviations, e.g. <abbrev>v. aux</abbrev>

    cmd     command name, e.g. chmod in Unix

    arg     command argument, e.g. <arg>-s</arg>

    kbd     something the use would have to type

    var     named place holder, e.g. <var>filename</var>

    dfn     defining instance of a term

    code    code example - usually shown in a fixed pitch font

    samp    sequence of literal characters usually in a variable
            pitch font

All  these tags require a matching closing tag like the other emphasis
elements, e.g.

<cmd>cmp</cmd>  [<arg>-l</arg>] [<arg>-s</arg>] <var>file1</var>
<var>file2</var>


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HTML+ Document Format                                            Raggett


5.7  Extending the Set of Logical Roles

When  translating from other SGML-based formats, documents may include
non-standard ele- ments e.g. PROPNAME for proper names. HTML+ browsers
will normally ignore such markup and process their contents as if these
tags weren't present. The RENDER element can be used to tell the
browser how to render such tags, e.g. 

    <RENDER TAG="PROPNAME" STYLE="I">

The  STYLE attribute is a comma separated list of presentation tag
names, i.e. one or more names from the list: I, B, U, S, SUP, SUB, TT.
Include P in the list of styles if the element needs a paragraph break.
Keeping non-standard markup in HTML+ documents may be useful for
indexing purposes. Note that the RENDER element isn't meant to apply
retrospectively.

5.8  Annotations

Authors  can include annotations which act to draw the readers attention
or which provide some additional comment on the main text of the
paragraph. There are two types:

    footnote    for additional information on some point
    margin      attention getter for this paragraph

When  printed out, these annotations appear as footnotes or margin notes
as their name implies, e.g. <footnote>This is an example of a footnote
</footnote>. For on-line use, browsers may show the annotation by a
hypertext button, e.g. a superscripted dingbat symbol or icon, which
when clicked reveals the annotation in a pop-up window. Footnotes and
margins can contain text with emphasis and images, but not other markup
such as paragraphs, lists or tables. The PANEL element in the previous
draft has been dropped. You can however, indicate that a hypertext link
should be rendered as a sidebar when printed out.

5.9  Images

Images  can be included as character like elements with text flowing
around the image, e.g.

    [Picture missing]  Before coming to CERN, Tim worked on, among other
    [in text version]  things, document production and text processing.
                       He developed his first hypertext system,
    "Enquire", in 1980 for his own use (although unaware of the existence
    of the term HyperText).  With a background in text processing,
    real-time software and communications,  Tim decided that high energy
    physics needed a networked hypertext system and  CERN was an ideal
    site for the development of wide-area hypertext ideas. Tim started
    the WorldWideWeb project at CERN in 1989. He wrote the application
    on the NeXT along with most of the communications software.


Internet Draft                     15                      November 1993
HTML+ Document Format                                            Raggett


This example is produced by the following piece of HTML+

    <p><img align=top src="http://spoof.cern.ch/people/tbl.gif"> Before
    coming to CERN, Tim worked on, among other things, document
    production and text processing. He developed his first hypertext
    system, "Enquire", in 1980 for his own use (although unaware of
    the existence of the term HyperText). With a background in text
    processing, real-time software and communications, Tim decided
    that high energy physics needed a networked hypertext system and
    CERN was an ideal site for the development of wide-area hypertext
    ideas. Tim started the WorldWideWeb project at CERN in 1989. He
    wrote the application on the NeXT along with most of the
    communications software.

The IMG element specifies an image via a URL. The ALIGN=TOP attribute
ensures that the top of the image is level with the top of the current
text line. You can also use ALIGN=MIDDLE to align the center of the
image with that of the current text line, and ALIGN=BOTTOM to align the
bottom of the image with the bottom of the current text line. Browsers
are not expected to apply text flow retrospectively, so using
ALIGN=MIDDLE and ALIGN=BOTTOM may overwrite previous lines of text. If
the ALIGN attribute is missing then ALIGN=TOP is assumed.

Not  all display types can show images. The IMAGE element behaves in the
same way as IMG but allows you to include descriptive text, which can
be shown on text-only displays:

    <image align=top src="http://spoof.cern.ch/people/tbl.gif">A photo
    of Tim Berners-Lee</image> Before coming to CERN, Tim worked on,
    among other things, document production and text processing. etc.

On text-only displays, the text within the IMAGE element can be shown
in place of the image:

    [A photo of Tim Berners-Lee] Before coming to CERN, Tim worked on,
    among other things, document production and text processing. etc.

The  SEETHRU attribute can be used to designate a chromakey so that the
image background matches the document background. This is an
experimental feature and the format of the attribute's value has yet to
be defined - suggestions are welcomed.

Images  can be made active in one of three ways

    o   The whole image can be made into a hypertext link

    o   Mouse/Pen clicks on the image can be passed to a WWW server

    o   Shaped hypertext buttons can be overlayed on the image


Internet Draft                     16                      November 1993
HTML+ Document Format                                            Raggett


Making  the entire image into an iconic hypertext button is simple:

  <a href="bigpic.giff"><image src="smallpic.gif">Our house</image></a>

In  this example, readers can click on a small picture embedded in the
document to see a larger version, which would take significantly longer
to retrieve. When using images as hypertext links, don't forget to
include a textual description. This is needed for the link caption for
peo- ple using text-only displays.

In  some cases, servers can handle mouse clicks or drags on the image.
This capability is signalled in the header information returned along
with the image data. You can also use the ISMAP attribute. This
mechanism and the ability to add shaped buttons are defined in detail
in the description of figures.

The  delay in connecting to the server for each image in turn can be
reduced by asking HTTP servers to include images with the HTML+
document as a MIME multipart message (include multipart/mixed with the
Accept: header in the request message).

5.10  Change Bars and Document Amendments

Change  bars are shown for parts of the document designated with the
CHANGED element. This can appear anywhere that normal text is allowed
(as shown by the %text; entity reference in the DTD):

    <changed id=z34>text including some changes<changed idref=z34>

The  same element is used to designate the start and end of changes,
using matched ID and IDREF attribute values. This mechanism avoids
syntactic problems that would arise from using a conventional start and
end tag pair, as changes to a document can span different levels of the
document's formal structure. Additional attributes may be used with the
CHANGED element to  hold related details, e.g. BY, WHEN, WHY, WHAT.

In  legal documents and amendments to proposed legislation, there is
often the need to show parts of the text as being removed or added to
the document. This is commonly shown using strike-through and
underlining respectively. The REMOVED and ADDED tags are provided for
this purpose:

    <P>This bill would require the Legislative Counsel, with the advice
    of the Joint Rules Committee of the Senate and Assembly, to make
    available to the public by means of access by way of
    <removed>computer modem</removed> <added>the largest nonproprietary,
    nonprofit cooperative public computer network,</added> specified
    information concerning bills, the proceedings of the houses and
    committees of the Legislature, statutory enactments, and the
    California Constitution.


Internet Draft                     17                      November 1993
HTML+ Document Format                                            Raggett


Which might be displayed (on a dumb terminal) as:

    This bill would require the Legislative Counsel, with the advice of
    the Joint Rules Committee of the Senate and Assembly, to make
    available to the public by means of access by way of
    <removed>computer modem</removed> <added>the largest nonproprietary,
    nonprofit cooperative public computer network,</added> specified
    information concerning bills, the proceedings of the houses and
    committees of the Legislature, statutory enactments, and
    the California Constitution.

Color enhancements may be used to further distinguish the amendments,
e.g. red lines for strike-through. This mechanism is not intended for
representing revision histories, which are better served by traditional
change control mechanisms.

5.11  Conditional Text

It  is often quite difficult to phrase the captions for hypertext
buttons so that they make sense when printed out. The ONLINE and
PRINTED elements can be used to define text which is for use only when
read on-line or on the printed page respectively:

 <online>click <a href="info.html">here</a>for more information.</online>
 <printed>Further information can be found in [Higgins 84b].</printed>

In many cases, you can find a way of phrasing the reference so that it
makes sense both ways. Browsers can help by referencing hypertext links
as footnotes when printed out. See the earlier description of the PRINT
attribute for the A tag.

5.12  Explicit Line Breaks

You  can make individual lines explicit with the <L> element, which
contains the text of the line in the same way that <P> contains the
text of the paragraph.

    <P>
    <L>22 The Avenue,
    <L>Harrow,
    <L>London, NW1 5ER

An  alternative is the <BR> element which acts as a forced line break. 

    <P>22 The Avenue<BR>
    Harrow,<BR>London, NW1 5ER

The  <L> element is useful when you want to name each line, e.g. <L
ID="L23">. You may also want to disable word wrap for the current
paragraph, as in <P WRAP=OFF>.


Internet Draft                     18                      November 1993
HTML+ Document Format                                            Raggett


6  Different Paragraph Styles

To  avoid all text appearing in the same style, HTML+ provides distinct
styles for quotes, abstracts, bylines and admonishments. All these
elements can contain multiple paragraphs:

6.1  Longer Quotations

When  you want to include a quotation that extends over more that one
paragraph, you should use the QUOTE element. Quoted text should
preferably be indented, and rendered using a distinctive font, e.g.

    <P>The following is a quotation from the forward by Yuri Rubinsky
    to "The SGML Handbook" by Charles F. Goldfarb, published by the
    Clarendon Press, Oxford, 1990.

    <QUOTE>The next five years will see a revolution in computing. Users
    will no longer have to work at every computer task as if they had
    no need or ability to share data with all their other computer tasks,
    they will not need to act as if the computer is simply a replacement
    for paper, nor will they have to appease computers or software
    programs that seem to be at war with one another.</QUOTE>

which  might be rendered as:

    The following is a quotation from the forward by Yuri Rubinsky to
    "The SGML Handbook" by Charles F.  Goldfarb, published by the
    Clarendon Press, Oxford, 1990.

      The next five years will see a revolution in computing. Users
      will no longer have to work at every  computer task as if they
      had no need or ability to share data with all their other computer
      tasks,  they will not need to act as if the computer is simply a
      replacement for paper, nor will they have to appease computers or
      software programs that seem to be at war with one another.

6.2  Abstracts

The  ABSTRACT element can be used to give an overview of a document and
typically follows a level one heading. It should be rendered in an
easily read font, distinct from normal text, and preferably indented.
An example is given in the next section.

6.3  Bylines

The  BYLINE element is similar to QUOTE and is used for information
about the author, e.g. contact details and release date. A common
convention is to include a hypertext link to a node with more
information about the author. Bylines can occur at the beginning or end
of a document, e.g:


Internet Draft                     19                      November 1993
HTML+ Document Format                                            Raggett


    <H1>HTML+ (Hypertext markup format</H1>

    <ABSTRACT>A proposed standard for a light weight delivery format
        for browsing and querying information in a web of globally
        distributed hypertext accessible over the Internet
    </ABSTRACT>

    <BYLINE>Editor: Dave Raggett dsr@hplb.hpl.hp.com</BYLINE>

6.4  Notes and admonishments

The  NOTE element is used when you want to draw the readers attention to
some point or other. For example:

    <note role="NOTE" src="info.gif">
    The "partial-window-name" parameter must exactly match the beginning 
    characters of the window name (as it appears on the title bar),
    including proper case (capital or lower letters) and any punctuation.
    </note>

This  is typically rendered as:

 ----------------------------------------------------------------------
 NOTE: The "partial-window-name" parameter must exactly match the 
 beginning characters of the window name (as it appears on the title
 bar), including proper case (capital or lower letters) and any
 punctuation.
 ----------------------------------------------------------------------

The  text of the ROLE attribute (if given) is inserted at the start of
the note in a bold font and followed by a colon. Typical roles are TIP,
NOTE, WARNING and ERROR. The SRC attribute may be used to name a URL or
URN as an icon which is displayed in the left margin at the start of
the note. An upright hand icon is often used for tips; a warning road
sign for warnings and a stop sign for errors. Horizontal rules are
drawn automatically to help readers distinguish the note from the
surrounding text. You can place horizontal rules in other parts of your
document using the <HR> element which can appear anywhere a <P> element
is allowed.

7  Lists

There  are three kinds of lists, which can be freely nested within one
another:

    o   Ordered lists - the list items are automatically numbered

    o   Unordered lists - bulleted or plain styles, in single or
        multiple columns

    o   Definition lists of terms and associated definitions


Internet Draft                     20                      November 1993
HTML+ Document Format                                            Raggett


7.1  Ordered Lists

The  OL element is used with LI for each item to represent ordered
lists:

    <OL>
        <LI>Wake up
        <LI>Get dressed
        <LI>Have breakfast
        <LI>Drive to work
    </OL>

which  is usually rendered as:

    1)  Wake up

    2)  Get dressed

    3)  Have breakfast

    4)  Drive to work

The  COMPACT attribute when present e.g. <OL COMPACT> has the effect of
reducing inter-item spacing. The numbering style is the responsibility
of the browser. Other styles use roman numerals or letters from the
alphabet in upper or lower case. One issue for browsers, is how to
render ordered lists, nested within a list of the same type. List item
text can't include headers,  see the DTD in Appendix I for details.

7.2  Bulleted Lists

Bulleted  lists are represented with the UL and LI elements:

    <UL>
        <LI>Wake up
        <LI>Get dressed
        <LI>Have breakfast
        <LI>Drive to work
    </UL>

which  is usually rendered as:

    o   Wake up

    o   Get dressed

    o   Have breakfast

    o   Drive to work


Internet Draft                     21                      November 1993
HTML+ Document Format                                            Raggett


The  COMPACT attribute when present e.g. <UL COMPACT> has the effect of
reducing inter-item spacing. The bullet style is the responsibility of
the browser, and normally an unordered list nested within a list of the
same type is given a different style (bullet, dash, box or check).
Authors can instead use the SRC attribute for the LI element to specify
an icon with a URL or URN, e.g. <LI SRC="folder.gif">. List item text
can't include headers, see the HTML+ DTD in Appendix I for details.

7.3  Plain Lists

Plain  lists without bullets are represented by the UL element together
with the PLAIN attribute, e.g. <UL PLAIN>. The WRAP attribute is used
for multi-column lists and should be WRAP=HORIZ for horizontally
wrapping of list items or WRAP=VERT for vertical wrapping of list
items, e.g.

    <UL PLAIN>
        <LI>icons1/
        <LI>icons2/
        <LI>icons3/
        <LI>src/
        <LI>xpm-3-paper.ps
        <LI>xpm-3.2-to-3.2a.patch
    </UL>

without  the WRAP attribute, this is rendered as:

    icons1/
    icons2/
    icons3/
    src/
    xpm-3-paper.ps
    xpm-3.2-to-3.2a.patch

with  <UL PLAIN WRAP=VERT> this would appear like:

    icons1/         icons3/             xpm-3-paper.ps
    icons2/         src/                xpm-3.2-to-3.2a.patch

with  WRAP=HORIZ it would appear like:

    icons1/         icons2/             icons3/
    src/            xpm-3-paper.ps      xpm-3.2-to-3.2a.patch

Everyday  familiarity with printed lists leads us to expect lists to be
organized into columns which are read top to bottom; horizontally
wrapped lists are seldom seen. Browsers are free to choose the number
of columns to match the current window size and item widths. If there
are N items and M columns then the longest column will have (N+M-1)/M
rows. This requires a  prepass through the list to count the items (and
optionally their maximum width). However, this information can be


Internet Draft                     22                      November 1993
HTML+ Document Format                                            Raggett


cached to avoid speed penalties when resizing the window or refreshing
the screen. You can use the SRC attribute for the LI element to specify
an icon for each item in the list, e.g. to show the type of each
document in a directory listing. 

For  convenience, the <MENU> and <DIR> elements can be used in place of
<UL PLAIN> and <UL PLAIN WRAP=VERT> respectively. 

7.4  Definition Lists

These  consist of pairs of terms and definitions, but can also be used
for plays as in:

    <DL>
        <DT>King Henry
        <DD>I myself heard the King say he would not be ransomed.
        <DT>Williams
        <DD>Ay, he said so, to make us fight cheerfully: but when our
            throats are cut he may be ransomed, and we none the wiser.
        <DT>King Henry
        <DD>If I live to see it, I will never trust his word after.
        <DT>Williams
        <DD>You pay him then! That's a perilous shot out of an
            elder-gun, that a poor and a private displeasure can do
            against a monarch! You may as well go about to turn the sun
            to ice, with fanning in his face with a peacock's feather.
            You'll never trust his word after! Come `tis a foolish
            saying.
    </DL>

This  could be rendered as:

    King Henry: I myself heard the King say he would not be
      ransomed.

    Williams: Ay, he said so, to make us fight cheerfully: but
      when our throats are cut he may be ransomed, and we none
      the wiser.

    King Henry: If I live to see it, I will never trust his word
      after.

    Williams: You pay him then! That's a perilous shot out of an
      elder-gun, that a poor and  private displeasure can do
      against a monarch! You may as well go about to turn the sun
      to ice, with fanning his face with a peacock's feather.
      You'll never trust his word after! Come `tis a foolish saying.

or  as:

    King Henry      I myself heard the King say he would not be


Internet Draft                     23                      November 1993
HTML+ Document Format                                            Raggett


                    ransomed.

    Williams        Ay, he said so, to make us fight cheerfully: but
                    when our throats are cut he may be ransomed, and
                    we none the wiser.

    King Henry      If I live to see it, I will never trust his word
                    after.

    Williams        You pay him then! That's a perilous shot out of an
                    elder-gun, that a poor and private displeasure can
                    do against a monarch! You may as well go about to
                    turn the sun to ice, with fanning his face with a
                    peacock's feather. You'll never trust his word
                    after!  Come `tis a foolish saying.

Browsers  should make allowance for the infrequent case when the term
text (DT) is longer than the definition text (DD) and wraps onto
subsequent lines. Note that you are allowed to have several consecutive
DT elements followed by a DD element, but you can't have DD without an
associated DT element, The COMPACT attribute as in <DL COMPACT> forces
the browser to use the former more compact style.

8  Figures

The  FIG element is similar to the IMAGE element, but acts as a
paragraph. The ALIGN attribute can be one of LEFT (the default),
CENTER, RIGHT or FLOAT. This determines whether the figure is flush
left, centered or flush right. If ALIGN=FLOAT the figure may float to
another more convenient location (and possibly zoomed or reduced in the
process). A caption can be defined  with the CAPTION element and
followed by text describing the figure for readers using text only
displays:

    <FIG ALIGN=FLOAT SRC="cat.gif">
        <CAPTION>"Not curried fish again!"<CAPTION>
        A cartoon of a scrawny cat with its tongue out saying ACK!
    </FIG>

    <P>The text in the following paragraphs will flow around the figure
    if there is enough room. The browser is free to position the caption at 
    the top, bottom or sides of the figure.

which  is rendered as:

    [                     ]  The text in the following paragraphs will
    [   picture missing   ]  flow around the figure if there is enough
    [                     ]  room. The browser is free to position the
    [                     ]  caption at the top, bottom or sides of the
                             figure.
    "Not curried fish again!"


Internet Draft                     24                      November 1993
HTML+ Document Format                                            Raggett


Note  that browsers can only support a limited range of image types.
Currently these are GIF and XBM (X bitmap format). This list will
evolve over time.

8.1  Active Areas

The  uppe left of the image is designated as x,y = (0, 0), with x
increasing across the page and y down the page. This choice was made
for continuity with the IMG element in HTML, to ensure a simple
migration path to HTML+. If points are given in real numbers, the lower
right corner of the image is taken as being (1.0, 1.0), otherwise, with
integer values the coordinates  are assumed to be in pixels. A simple
test to distinguish the two schemes is to check if a "." character
occurs anywhere in the list of points. Using scaled coordinates is much
safer as the pixel extent of an image may alter, e.g. as a result of
format negotiation with the server.

For  some images, HTTP servers will be able to handle mouse/pen clicks
or drags on the image. This is signalled in the header information
returned along with the image data. Alternatively, the ISMAP attribute
can be used to signal this capability. The mouse click is sent to the
server indicated by the URL in the SRC attribute, using the same URL
plus the suffix "?x=X&y=Y" where X and Y are the coordinates of the
click event. Mouse drags can be used
 to designate a rectangular region of the image. In this case the suffix
takes  the form: "?x=X&y=Y&w=W&h=H" where (X, Y) is the upper left of
the rectangle, and (W, H) define its width and height. The ISMAP
mechanism is useful when the active regions in the image change their
boundaries with time, e.g.

    <fig ismap src="weather.gif">
        <caption>Click on your area for a local forecast</caption>
        Todays weather map for the US.
    </fig>

8.2  Placing Hypertext Buttons on Images

The  A element can be used to define shaped buttons on top of images.
The shape is defined by an arbitrary polygon and specified via the
SHAPE attribute, e.g.

   <FIG SRC="test.gif">
      <CAPTION>Click on the triangle or the rectangle</CAPTION>
      A line drawing with a
      <A SHAPE="0.35,0.1&0.1,0.8&0.35,0.8"    HREF="button1.html">
      triangle</A>                    and a
      <A SHAPE="0.5,0.25&0.5,0.5&0.8,0.5&0.8,0.25" HREF="button2.html">
      rectangle</A>
   </FIG>


Internet Draft                     25                      November 1993
HTML+ Document Format                                            Raggett


Which  could be rendered as:

    [ Picture missing in text file ]

The  example uses scaled coordinates, and shows how you give the
vertices of the polygon defining the shape of the button. Like the
ISMAP mechanism, you can use pixel-based coordinates by using integer
numbers throughout. Note that clicks on shaped buttons take precedence
over the ISMAP mechanism for sending events to the server. An efficient
algorithm for testing if a mouse/pen click lies inside a polygon is
given as a C routine in Appendix III.

8.3  Possible extensions

In  future, HTML+ may be extended to support simple drawings with
embedded hypertext links. One idea would be a line drawing primitive
using the SHAPE attribute. A better approach is to extend existing
drawing formats such as the ANSI Computer Graphics Metafile format
(CGM) or Adobe's PDF to include URL based hypertext links. This
extended format could then be used for figures within HTML+ documents.

The  use of the MIME multipart message format would also help to speed
up the display of figures by sending image data at the same time as the
HTML+ document. Another possibility would be to allow image data to be
embedded in the document using an EMBED element in place of the SRC
attribute. Binary data could be represented using the MIME character
encoding or the more compact ASCII base 85 encoding, as used in Adobe's
PDF. The drawback with this approach is the inability to use format
negotiation. As a result, the EMBED element has been dropped from the
current draft.

9  Tables

Tables  are specified using the TABLE element. This allows you to define
a caption and to differentiate header and data cells. Cells may
contain, text, multiple paragraphs, lists and headers. Adjacent cells
can be merged, e.g. to define a header which spans two columns. A
simple table could look like:

Table  1: A simple table

       -------------------------------
       | Year   |    Month   |   Day |
       -------------------------------
       | 1972   |    June    |  23rd |
       -------------------------------
       | 1982   |   October  |  7th  |
       -------------------------------

This  is defined by the markup:


Internet Draft                     26                      November 1993
HTML+ Document Format                                            Raggett


    <table border>
        <caption>A simple table</caption>
        <th>Year <th>Month <th>Day <tr>
        <td>1972 <td>June <td>23rd <tr>
        <td>1982 <td>October <td>7th
    </table>

The  BORDER attribute acts as a hint to the browser to draw lines
enclosing each cell. The TH ele- ment precedes header cell text and the
TD element precedes data cell text. The TR element is used to separate
table rows. By default text is centered in each cell. Header text
should be shown emphasised, e.g. the browser could use a bold sans
serif font for headers and a serif font for the data cells. The next
example shows how cells can be merged with their neighbors:

Table  2: A more complex table

                        average                  other
                height          weight          category

    males        1.9            0.003             yyy

    females      1.7            0.002             xxx


This  table is defined by the markup:

 <table>
  <caption>A more complex table</caption>
  <th rowspan=2><th colspan=2>average<th rowspan=2>other<br>category<tr>
  <th>height <th>weight <tr>
  <th align=left>males <td>1.9 <td>0.003 <td>yyy <tr>
  <th align=left>females <td>1.7 <td>0.002 <td>xxx
 </table>

The  first cell (a header cell) is merged with the cell below it: <th
rowspan=2>. Note that this merged cell is empty - the definition of the
next column for the first row starts immediately. Looking again at the
first row, the second column is merged with the third: <th colspan=2>.
The definition for the third column is skipped as it was covered by the
merged cell. The fourth column/first row is also merged, this time with
the next row: <th rowspan=2>. The <BR> element has been used here to
force a line break between other and category. The <TR> element
signifies the end of the first row and the beginning of the second.
Note that empty cells at the end of a row can be omitted as the <TR>
element unambiguously marks the end of the row.

The  second row only contains definitions for the second and third
columns since the others were merged with cells on the preceding row.
The general rule is to avoid defining any cell twice. The last two rows
start with headers and the align=left attribute ensures that the


Internet Draft                     27                      November 1993
HTML+ Document Format                                            Raggett


browser will align these headers to the left of their cells. The ALIGN
attribute can be one of  LEFT, CENTER or RIGHT, with CENTER as the
default. It can be used with both TH and TD.

9.1  Implementation Issues for Tables

Browsers  need a prepass through the table markup to count the number of
columns and determine their widths. A simple algorithm that takes
merged cells into account will suffice. Text fields wrap to fit their
columns, which should be sized to best match current window width. This
information should be cached to avoid speed penalties during subsequent
screen refresh/ window resize operations. Browsers can ignore alignment
hints if required, and using a fixed pitch font may speed up the sizing
step.

The  number of columns is given by the row with the largest number of
<TH> and <TD> elements, remembering to add in merged cells. The widths
of columns are evaluated by finding the minimum and maximum widths
needed for each cell, and hence the minimum and maximum width for the
column as a whole. All this can be done during a single pass through
the <TABLE> element. Caching these min/max values for each column then
permits the browser to instantly adjust the table when the window is
resized.

10  Fill-out Forms and Input fields

Forms  are composed by placing input fields within paragraphs,
preformatted/literal text, lists and tables. This gives considerable
scope in designing the layout of forms. Each field is defined by an
INPUT element and must have an NAME attribute which uniquely names the
field in the document. Additional optional attributes can be used to
specify the type of the field (defaults to free text), its
size/precision, its initial value and whether the field is currently
disa- bled or in error:

  <FORM ACTION="mailto:www_admin@info.cern.ch">
    <MH HIDDEN>Subject: WWW Questionaire</MH>

    Please help up to improve the World Wide Web by filling in the
    following questionaire:
    <P>Your organization? <INPUT NAME="org" SIZE="48">
    <P>Commercial? <INPUT NAME="commerce" TYPE=checkbox>
            How many users? <INPUT NAME="users" TYPE=int>
    <P>Which browsers do you use?
    <OL>
     <LI>X Mosaic <INPUT NAME="browsers" TYPE=checkbox VALUE="xmosaic">
     <LI>Cello <INPUT NAME="browsers" TYPE=checkbox VALUE="cello">
     <LI>Others <TEXTAREA NAME="others" COLS=48 ROWS=4></TEXTAREA>
    </OL>
    A contact point for your site: <INPUT NAME="contact" SIZE="42">
    <P>Many thanks on behalf of the WWW central support team.


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HTML+ Document Format                                            Raggett


    <P ALIGN=CENTER><INPUT TYPE=submit> <INPUT TYPE=reset>
  </FORM>

This  fictitious example is a questionnaire that will be emailed to
www_admin@info.cern.ch. The FORM element is used to delimit the form.
There can be several forms in a single document, but the FORM element
can't be nested. The ACTION attribute specifies a URL that designates
an HTTP server or an email address. If missing, the URL for the
document itself will be  assumed. The effect of the action can be
modified by including a method prefix, e.g. ACTION="POST http://....".
This prefix is used to select the HTTP method when sending the form's
contents to an HTTP server. Would it be cleaner to use a separate
attribute, e.g. METHOD?

Servers  can disable forms by sending an appropriate header or by an
attribute on the optional HTMLPLUS element at the very start of the
document, e.g.

    <htmlplus forms=off>.

The  MH element can be used to specify RFC 822 mail headers that are
included when sending the form's content either as an email message or
as a HTTP request, e.g.

    <MH HIDDEN>
    Subject: WWW Questionnaire
    Priority: Low
    </MH>

The  MH element can contain several headers separated by line breaks.
The text within the MH element is transcribed directly, preserving
spaces, tabs and line breaks, with each line terminated by a CR LF pair
as per the RFC 822 guidelines. The preceding example of a form might be
rendered as:


 ----------------------------------------------------------------------
 Please help us to improve the World Wide Web by filling in the
 following questionnaire:

 Your organization: [                                           ]
 Commercial [N]  How many users? [             ]

 Which browsers do you use?

     1)  X Mosaic [ ]

     2)  Cello


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HTML+ Document Format                                            Raggett


     3) Others [                                         ]
               [                                         ]
               [                                         ]
               [                                         ]

 A contact point for your site? [                                     ]

 Many thanks on behalf of the WWW Central support team.

                 (Submit)       (Reset)
 ----------------------------------------------------------------------

Here,  the <P> and <OL> elements have been used to lay out the text and
input fields. The browser has changed the background color within the
FORM element to distinguish the form from other parts of the document.
The browser is responsible for handling the input focus, i.e. which
field will currently get keyboard input.

For many platforms there will be existing conventions for forms, e.g.
tab and shift-tab keys to move the keyboard focus forwards and
backwards between fields, while an Enter key submits the form. In the
example, the Submit and Reset buttons are specified explicitly with
special purpose fields. The Submit button is used to email the form or
send its contents to the server as specified by the ACTION attribute,
while the Reset button resets the fields to their initial values. When
the form consists of a single text field, it may be appropriate to
leave such buttons out and rely on the Enter key.

The  INPUT element has the following attributes:

    NAME        Symbolic name used when transferring the form's
                contents. This attribute is always needed and
                should uniquely identify this field.

    TYPE        Defines the type of data the field accepts. Defaults
                to free text.

    SIZE        Specifies the size or precision of the field according
                to its type.

    MAXLENGTH   The maximum number of characters that will be accepted
                as input. This can be greater that specified by SIZE,
                in which case the field will scroll appropriately.
                The default is unlimited.

    VALUE       The initial value for the field, or the value when
                checked for checkboxes and radio buttons. This
                attribute is required for radio buttons.

    CHECKED     When present indicates that a checkbox or radio
                button is selected.


Internet Draft                     30                      November 1993
HTML+ Document Format                                            Raggett


    DISABLED    When present indicates that this field is temporarily
                disabled. Browsers should show this by "greying it"
                out in some manner.

    ERROR       When present indicates that the field's initial value
                is in error in some way, e.g. because it is
                inconsistent with the values of other fields. Servers
                should  include an explanatory error message with the
                form's text.

    SRC         A URL or URN specifying an image - for use only with
                TYPE=IMAGEMAP.

    ALIGN       Vertical alignment of the image - for use only with
                TYPE=IMAGEMAP.

The  following types of fields can be defined with the TYPE attribute
(upper or lower case):

    TEXT        Single line text entry fields. Use the SIZE attribute
                to specify the visible  width in characters, e.g.
                SIZE="24" for a 24 character field. The MAX attribute
                can be used to specify an upper limit to the number of
                characters  that can be entered into a text field, e.g.
                MAX=72. Use the TEXTAREA element for text fields which
                can accept multiple lines (see below).

    INT         For entering integer numbers, the maximum number of
                digits can be specified with the SIZE attribute
                (excluding the sign character), e.g. size=3 for a
                three digit number.

    FLOAT       For fields which can accept floating point numbers.

    DATE        Fields which can accept a recognized date format.

    URL         For fields which expect document references as URLs or
                URNs.

    CHECKBOX    Used for simple Boolean attributes, or for attributes
                which can take multiple values at the same time. The
                latter is represented by a number of checkbox fields
                each of which has the same NAME.

    RADIO       For attributes which can take a single value from a set
                of alternatives. Each  radio button field in the group
                should be given the same NAME.

    RANGE       This allows you to specify an integer range with the
                MIN and MAX attributes,  e.g. MIN=1 MAX=100. Users can


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HTML+ Document Format                                            Raggett


                select any value in this range.

    IMAGE       This allows you to specify an image field upon which
                you can click with a  pointing device. The SRC and
                ALIGN attributes are exactly the same as for the IMG
                and IMAGE elements. The symbolic names for the x and
                y coordinates of the click event are specified with
                name.x and name.y for the name  given with the NAME
                attribute. The VALUE attribute is ignored.

    SCRIBBLE    A field upon which you can write with a pen or mouse.
                The size of the field  in millimeters is given as
                SIZE=width,height. The units are absolute as they
                relate to the dimensions of the human hand, rather
                than pixels of varying resolution. The scribble may
                involve time and pressure data in addition to the basic
                ink data. You can use scribble for signatures or
                sketches. The field can be initialised by setting the
                SRC attribute to a URL which contains the ink. The
                VALUE attribute is ignored.

    AUDIO       This provides a way of entering spoken messages into
                a form. Browsers might show an icon which when clicked
                pops-up a set of tape controls that  you can use to
                record and replay messages. The initial message can be
                set by specifying a URL with the SRC attribute. The
                VALUE attribute is ignored.

    SUBMIT      This is a button that when pressed submits the form. It
                is provided as a kind  of field to offer authors some
                control over the location of this button. You can use
                an image as a submit button by specifying a URL with
                the SRC attribute.

    RESET       This is a button that when pressed resets the form's
                fields to their initial values as specified by the
                VALUE attribute. You can use an image as a reset
                button by specifying a URL with the SRC attribute.

When you need to let users enter more than one line of text, you should
use the TEXTAREA element, e.g.

    <TEXTAREA NAME="address" ROWS=64 COLS=6>
        Hewlett Packard Laboratories
        1501 Page Mill Road
        Palo Alto, California 94304-1126
    </TEXTAREA>

The  text up to the end tag is used to initialize the field's value.
This end tag is always required even if the field is initially blank.
The ROWS and COLS attributes determine the visible dimension of the


Internet Draft                     32                      November 1993
HTML+ Document Format                                            Raggett


field in characters. Browsers are recommended to allow text to grow
beyond these limits by scrolling as needed. In the initial design for
forms, multi-line text fields were supported by the INPUT element with
TYPE=TEXT. Unfortunately, this causes problems for fields with long
text values as SGML limits the length of attribute literals. The HTML+
DTD allows for up to 1024 characters (the SGML default is only 240
characters!).

The  RADIO and CHECKBOX fields can be used to specify multiple choice
forms in which every alternative is visible as part of the form. An
alternative is to use the SELECT element which is generally rendered in
a more compact fashion as a pull down combo list. Every alternative is
represented by the OPTION element, e.g.

    <SELECT NAME="flavor">
        <OPTION>Vanilla
        <OPTION>Strawberry
        <OPTION>Rum and Raisin
        <OPTION>Peach and Orange
    </SELECT>

The  SEVERAL attribute is needed when users are allowed to make several
selections, e.g. <SELECT SEVERAL>. The ERROR attribute can be used to
indicate that the initial selection is in error in some way, e.g.
because it is inconsistent with the values of other fields.

The  OPTION element can take the following attributes:

    SELECTED        Indicates that this option is initially selected.

    DISABLED        When present indicates that this option is
                    temporarily disabled. Browsers should show this
                    by "greying it" out in some manner.

10.1  Sending form data to an HTTP server

The  form contents are expressed as a property list of attribute names
and values. Radio buttons and checkboxes are left out of the list when
unchecked. This ensures that only the selected radio button contributes
a name=value pair. Omitting the VALUE attribute for a checkbox field
causes the field when checked to appear as a name without a value (this
is appropriate for Boolean attributes). Currently, there are two ways
of transferring form contents to an HTTP server:

    o   As a suffix on the URL given by the ACTION attribute

    o   As a multipart MIME message

In  the first approach, the property list is encoded as a sequence of
name=value elements separated by the "&" character. The values for the
form's fields are sent as a search string, e.g.


Internet Draft                     33                      November 1993
HTML+ Document Format                                            Raggett


    URL?org=Acme%20Foods&commerce&users=42

Note  that "=", "&" and space characters in attribute names and values
should be escaped by "%" followed by the hexadecimal code for the
character in question, e.g. "%20" should be used in place of the space
character. IMAGE fields are only included in the list when clicked, and
give rise to something matching:

    URL?name.x=23&name.y=29

They  can be used as iconic controls for other images or data. The
object-name.property-name notation paves the way for more complex input
controls in the future. In the near future, for- mat negotiation will
not change the number of pixels in an image, so using pixel based
coordi- nates is okay. In the longer term, scaled coordinates in the
range 0 to 1.0 may prove safer.

Multipart  MIME messages are necessary if the form contains scribble or
audio fields. Form data can be sent in the same name=value
representation as described above. For scribble and audio fields, the
value identifies a subsequent part in the multipart message, as
specified by the Content-ID: header for each part. Another approach is
to send just the SGML elements used to define form fields, i.e. the
INPUT, TEXTAREA and SELECT elements. The Content-ID:  headers are used
to define dummy URLs. It may be possible for servers to use this
approach to update forms being viewed by a browser without having to
send the entire document.

10.2  Sending a form via Electronic Mail

In  this case, the form needs to be viewable on ordinary mail readers.
The form should be converted to ASCII and mailed as a plain text
message, preceded by the headers as specified by the MH element. Each
INPUT field is copied as text and delimited by the "[" and "]"
characters. An longer term alternative is to send the HTML+ document
as a MIME message, along with the current values for each field.

11  Literal and Preformatted Text

Preformatted  text started off in HTML with a simple mechanism for
showing computer output, for which the spaces and line breaks were
significant in determining the layout. The desire to offer Unix manual
pages as hypertext forced a rethink. The next version supported
character emphasis and embedded hypertext buttons. HTML+ adds the
capability to use variable pitch fonts and to set up tab stops.

The  LIT element is rendered in a proportional font, e.g.

    <LIT>
    From Oberon in fairyland,


Internet Draft                     34                      November 1993
HTML+ Document Format                                            Raggett


       The king of ghosts and shadows there,
    Mad Robin I, at his command,
       Am sent to view the night sports here.
          What revel rout
          is kept about,
       In every corner where I go,
          I will o'ersee
          And merry be
       And make good sport, with ho, ho, ho!
    </LIT>

This  is rendered literally as:

    From Oberon in fairyland,
       The king of ghosts and shadows there,
    Mad Robin I, at his command,
       Am sent to view the night sports here.
          What revel rout
          Is kept about,
       In every corner where I go,
          I will o'ersee
          And merry be
       And make good sport, with a ho, ho, ho!

The  ability to set tab stops in LITeral text makes it much easier to
write filters that convert documents written on word processors into
HTML+. Tab stops can be set by the TAB element and apply for the scope
of the LIT element, e.g.

<tab  at=40 align=right>

The  AT attribute specifies the position of the tab stop, as measured
from the left margin in terms of the width of a capital M. The ALIGN
attribute can be LEFT, CENTER or RIGHT, defaulting to LEFT. These have
the conventional meaning as used on most word processors. If greater
control over fonts and layout is needed then authors should make a
hypertext link to a document written in a page description format like
Adobe's PDF.

For  computer output or plain text files, you should use the PRE element
which is rendered in a fixed pitch font. The following is part of the
man page for the Unix ls command:

<PRE> 
 The next 9 characters are interpreted as three sets of three
 bits each which identify access permissions for owner,
 group, and others as follows:

 +------------------ 0400 read by owner (<B>r</B> or <B>-</B>)
 | +---------------- 0200 write by owner (<B>w</B> or <B>-</B>)
 | | +-------------- 0100 execute (search directory) by owner


Internet Draft                     35                      November 1993
HTML+ Document Format                                            Raggett


 | | |                  (<B>x</B>, <B>s</B>, <B>S</N>, or <B>-</B>)
 | | | +------------ 0040 read by group (<B>r</B> or <B>-</B>)
 | | | | +---------- 0020 write by group (<B>w</B> or <B>-</B>)
 | | | | | +-------- 0010 execute/search by group
 | | | | | |                 (<B>x</B>, <B>s</B>, <B>S</B>, or <B>-</B>)
 | | | | | | +------ 0004 read by others (<B>r</B> or <B>-</B>)
 | | | | | | | +---- 0002 write by others (<B>w</B> or <B>-</B>)
 | | | | | | | | +-- 0001 execute/search by others
 | | | | | | | | |           (<B>x</B>, <B>t</B>, <B>T</B>, or <B>-</B>)
 | | | | | | | | |
 r w x r w x r w x

</PRE> 

This  is rendered as

 The next 9 characters are interpreted as three sets of three
 bits each which identify access permissions for owner,
 group, and others as follows:

 +------------------ 0400 read by owner (r or -)
 | +---------------- 0200 write by owner (w or -)
 | | +-------------- 0100 execute (search directory) by owner
 | | |                  (x, s, S, or -)
 | | | +------------ 0040 read by group (r or -)
 | | | | +---------- 0020 write by group (w or -)
 | | | | | +-------- 0010 execute/search by group
 | | | | | |                 (x, s, S, or -)
 | | | | | | +------ 0004 read by others (r or -)
 | | | | | | | +---- 0002 write by others (w or -)
 | | | | | | | | +-- 0001 execute/search by others
 | | | | | | | | |           (x, t, T, or -)
 | | | | | | | | |
 r w x r w x r w x


The  SEE ALSO section of the Unix manual pages can be processed to make
references to other manual pages into hypertext buttons using the <A>
element (see section 5.2). The example shows how character emphasis can
be added to literal or preformatted text.

12  Mathematical Equations

Currently,  the best way of including equations in HTML documents is to
first write the document in LaTeX and then use the latex2html filter to
create the corresponding HTML document, together with the equations as
a number of bitmap files. The previous draft of the HTML+ specification
described a way of embedding LaTeX equations in HTML+ documents.
Unfortunately, it now seems too cumbersome to form a practical
solution, and has been dropped.


Internet Draft                     36                      November 1993
HTML+ Document Format                                            Raggett


The  following is a preliminary proposal for representing equations
directly as HTML+ using an SGML-based notation, inspired by the
approach taken by LaTeX. It is intended to cover the majority of users
needs, rather than aiming for complete coverage. This makes it
practical to use a simplified notation compared with richer notations,
e.g. the ISO 12083 Maths DTD. An  experimental browser supporting the
MATH element is being developed at CERN.

Consider  the equation:
                                            -st
    H(s) = integral from 0 to infinity of  e    h(t) dt

This  can be represented as:

    <math>
        H(s) = &int;<sub>0</sub><sup>&infin;</sup>
               e<sup>-st</sup> h(t) dt
    </math>

The  mathematical symbols are given with their standard ISO entity
names. SUB and SUP are used to specify subscripts and superscripts. For
integral signs and related operators, the subscript/superscript text is
centered over the symbol, otherwise it appears to the right as shown in
the preceding example. The BOX and OVER elements allow you to define
more complex equations, as in:

     dV                        V   - V
        out          ( Kappa (  in    out))
    C ----- = I  tanh( -------------------)
       dt      b     (         2          )

which  is represented by:

    <math>
        C <box>dV<sub>out</sub><over>dt</box> = I<sub>b</sub>
        &tanh;(<box>&kappa;(V<sub>in</sub> - V<sub>out</sub>)
                    <over>2</box>)
    </math>

The  BOX element can be used to generally group items and can be thought
of as non-printing parentheses. The OVER element is optional and
divides the box into numerator and denomina- tor. The ARRAY element is
used to specify arrays for expressions like:

            ( |x    x  | )
            ( | 11   12| )
            ( |        | )
            ( |x    x  | )
            ( | 21   22| )
            (            )
            (     y      )


Internet Draft                     37                      November 1993
HTML+ Document Format                                            Raggett


            (            )
            (     z      )

The  ARRAY element has a single attribute ALIGN which specifies the
number of columns and the alignment of items within the columns. For
each column there is a single letter that specifies how items in that
column should be positioned: c for centered, l for flush left or r for
flush right. Each item in the array must follow an <ITEM> element.

The  preceding example is represented by:

    <math>
        (<array align="c"> <item>
                &ldet;<array align="cc">
                        <item>x<sub>11</sub>
                        <item>x<sub>12</sub>
                        <item>x<sub>21</sub>                    
                        <item>x<sub>22</sub>
                </array><rd>&rdet;
                <item> y <item> z
        </array>)
    </math>

The  browser is responsible for working out the vertical and horizontal
spacing required for the array. Parentheses are stretched to match the
size of the array. Arrays can be used only in the context of the MATH
element. The TABLE element should be used for other contexts.

Spaces  are significant within the MATH element, and used for
disambiguation, as can be seen in the following two examples:

    integral from i to j of x      &int;<sub>i</sub>i<sup>j</sup> x

                 j
    integral of   x                &int; <sub>i</sub>i<sup>j</sup>x
                 i

Authors  can adjust the default horizontal spacing with the ISO
entities: &thinsp; for thin space (1/6 em) and &hairsp; for hair space.
Horizontal, diagonal and vertical ellipsis are possible with &hellip;
&dellip; and &vellip; respectively. Common functions like sin, log and
tanh should be rendered in a non-italic font. These functions are
defined by their entity  namesakes. Additional elements are needed to
represent roots and for over and under lining.

An  open question is how to render maths on dumb terminals. One approach
is to translate into an existing convention such as Mathematica.
Another is to write equations as they would be spoken aloud. For GUI
displays, browsers need to be able to show characters in at least two
point sizes as well as being able to stretch parentheses and integral
signs etc. to various sizes.  The processing time needed to size and


Internet Draft                     38                      November 1993
HTML+ Document Format                                            Raggett


position symbols suggests that caching may be useful to speed up
subsequent scrolling and refresh operations. 

Comments  from mathematicians are welcomed. Widespread support for
formulae is likely to be delayed until most platforms support the
relevant symbols fonts (or Unicode). 

13  Indexing

A  good index plays an important role in helping you find your way to
the material you need. It allows you to type in one or more keywords to
see a list of matching topics. The ability to view an index directly
allows you to gain a feeling for what is covered, and lets you dip in
and out of the associated document. Full text indexes like WAIS are
easy to create, but don't give you this flexibility since the index
itself cannot be viewed directly.

Generating  a conventional index for a document is a skilled task, and
HTML+ allows authors to include directives for automatically creating
hypertext indexes. These directives can be included in many HTML+
elements, such as headers, paragraphs and character emphasis using the
INDEX attribute. This allows each such element to be referenced in the
index under primary or secondary keys, e.g.

    <h3 id="z23" index="Radiation damage/shielding from as difficult">
    Radiation shielding</h3>

This  can be used to generate an index like:

    Radiation damage
        classical target theory
        dominance of
        in molecular mills
        shielding from as difficult
        simple lifetime model
        track-structure lifetime model

    Radicals
        and so on ...

In  many cases, a given key will be associated with more than one part
of the document. In this case you can either use secondary keys to
disambiguate the references, as shown above, or allow the indexing
program to generate its own names for each reference, e.g. (a), (b),
(c), ...

The  indexing program creates an HTML+ file that can then be linked to
the documents it was produced from. The program may also generate a
list of references from occurrences of the CITE element. These can be
simply ordered alphabetically. Sophisticated bibliographic references
are beyond the scope of HTML+ as they require a much richer system of


Internet Draft                     39                      November 1993
HTML+ Document Format                                            Raggett


markup.

14  Document declarations

It  is recommended that HTML+ documents start with the following
external identifier, indicating that the document conforms to the HTML+
DTD. This will ensure that other SGML parsers can process HTML+
documents, without needing to include the DTD with each document.

    <!DOCTYPE htmlplus PUBLIC "-//Internet/RFC xxxx//EN">

There  are several elements that can only occur at the start of the
document before any headers or text elements:

14.1  HTMLPLUS

This  element if present must follow immediately after the DOCTYPE
declaration. It can be used to disable form filling:

    <htmplus forms=off>

Another  idea is to provide a VERSION attribute for specifying the
version number of HTML+ in used by this document. This would provide an
alternative to including the version number in the public name given
with the DOCTYPE element.

14.2  The HEAD and BODY elements

These  may be used to delimit the document declarations and document
body with the HEAD and BODY elements respectively, e.g.

    <HEAD>
        <ISINDEX>
        <LINK REL="Next" HREF="...">
        etc.
    </HEAD>

    <BODY>
        body elements go here
    </BODY>

14.3  TITLE

This  element is used to define the title of the current document. and
is often used as the win- dow banner for window-based displays. There
may be only one title in any node, and it should identify the content
of the node in a fairly wide context. No markup is permitted within
title text, although character entity references may be used for
accented characters etc.

14.4  ISINDEX


Internet Draft                     40                      November 1993
HTML+ Document Format                                            Raggett


The  ISINDEX element specifies that the URL given with the HREF
attribute is searchable, e.g. <ISINDEX HREF="glossary.html">. If the
HREF attribute is missing, the URL for this document is assumed.
Servers may also indicate that the current document is searchable via
the HTTP headers returned with the document. Browsers should allow
users to enter a search string of one or more keywords. When the user
presses the Return key, the browser maps any  spaces to "+", and
appends this string to the designated URL and sends it to the server,
e.g.

    URL?word+word+word

This  mechanism has to a large extent been superseded by the FORM
element. There are still good reasons for keeping it in HTML+. In
particular, when reading a long document, having the search field
always visible, makes it much easier for people to enter search
strings, than if they first had to scroll to the part of the document
which included a search form.

14.5  NEXTID

The  NEXTID element is used by browsers that automatically generate
identifiers for anchor points. It specifies the next identifier to use,
to avoid possible confusion with older (deleted) values, e.g. <nextid
n="id56">. The identifier should take the form of zero or more letters
followed by one or more digits. The numeric suffix should be
incremented to generate succes- sive identifiers.

14.6  BASE

The  HREF attribute of the BASE element gives the full URL of the
document, and is added by the browser when the user makes a local copy.
Keeping the full URL is essential when subsequently viewing the copied
document as it allows relative URLs to be resolved to their original
references, e.g. <BASE HREF=URL>.

14.7  LINK

This  provides a means of describing the relationship between this
document and other documents, and has the same attributes as the <A>
element (see section 5.2). A document can have multiple LINK elements.
Typical uses are to indicate authorship, related indexes and
glossaries, older or more recent versions etc. Another use is to
indicate a stylesheet that contains the  author's layout preferences,
e.g. for headers and multi-columns displays. Links can also be used to
indicate a static tree structure of documents with relationships such
as "parent", "next" and "previous", e.g. <LINK HREF=URL REL="next">

The  standard values for the REL attribute are (case insensitive):


Internet Draft                     41                      November 1993
HTML+ Document Format                                            Raggett


    UseIndex       The linked document can be used as an index for
                   this document. There may be several such indexes.
                   The TITLE attribute should be used to name each
                   index, e.g. in menus and dialog boxes. This
                   relationship  implies the document is searchable,
                   and the browser should provide a means for users
                   to type in one or more keywords. The index may be
                   a full text WAIS index or a conventional hypertext-
                   based index.

    UseGlossary    The linked document can be used to answer glossary
                   queries for this document. Typically invoked by a
                   double click on a word, or by drag selection,
                   followed by clicking a menu item. There may be
                   several such indexes. The TITLE attribute should be
                   used to name each index, e.g. in menus and dialog
                   boxes.

    Contents       The linked document acts as a contents page for a
                   number of related documents. The browser should make
                   this available as a button on a toolbar or as an
                   entry in a navigation menu. The TITLE attribute can
                   be used to override the default "Contents" name.

    Next           The linked document is next on a path of documents.
                   Browsers should make this available as a button on a
                   toolbar or as an entry in a navigation menu.

    Previous       The linked document is the previous one to the
                   current document on a path of documents. Browsers
                   should make this available as a button on a toolbar
                   or as an entry in a navigation menu.

    Parent         The linked document is at the next level up in a
                   hierarchy of documents. Browsers should make this
                   available as a button on a toolbar or as an entry
                   in a navigation menu. There may be several such
                   parents. The TITLE attribute should be used to
                   name each such document.

    Bookmark       The URL specified by the HREF attribute is a
                   bookmark, which is named by the TITLE attribute.
                   Browsers should make these available as buttons on
                   a toolbar or as entries in a navigation menu.

    Made           Defines who is the "maker" of this document. The
                   HREF attribute should give an appropriate URL e.g.
                   "mailto:dsr@hplb.hpl.hp.com".  Browsers can use
                   this to allow people to mail or post comments to
                   the author of the document.


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    Help           Associates a help document with this node.

Sometimes  it may be useful to specify a hypertext link separately from
the text associated with the start of the link. For example a sidebar
could be associated with a given paragraph as follows:

    <LINK IDREF="z36" REL="Sidebar" HREF="sidebar.html">

The  IDREF attribute localizes the link to an element in the current
document with a specific identifier (as defined with the ID attribute).
In the absence of the IDREF attribute, the link is associated with the
current document as a whole.

Other suggestions for LINK currently lie outside this proposal, pending
further work. In some cases, LINK elements may be implied by the
context in which this document was reached. This is explained in
section 15.

15  Dealing with Large Documents

Many  classic works are available over the Internet, now that their
copyright has expired. Downloading these as large documents is time
consuming, and a better strategy is to split them up into smaller
pieces. Other people have lots of paper documents and wish to make them
available electronically. While it is easy to scan these documents in,
the size of the images makes them tedious to transfer over the network.
Once again, time can be saved by avoiding the need to download the
whole document at once. HTML+ makes it easy to do this with explicit or
implicit links between the pieces that make up the complete document.

A  book might have the following pieces:

    o   `Cover page'

    o   About the author

    o   Copyright and publishing details

    o   Table of contents

    o   Foreword

    o   Preface

    o   Acknowledgement

    o   One or more chapters

    o   One or more appendices

    o   Bibliography


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    o   Glossary

    o   Index

Each  of these could be held as separate HTML+ subdocuments. The table
of contents should obviously include hypertext links to other parts of
the book rather than page numbers. You can define a linear sequence
through each of these subdocuments by including LINK elements with
REL=NEXT and REL=PREVIOUS. This will allow readers to read through each
part of the book in turn. You should also include LINKs to the table of
contents (REL=CONTENTS) and other key parts (using REL=BOOKMARK).

Generating  a hypertext version of the index may prove time consuming,
and it may be simpler to offer a full text search facility instead. The
INDEX attribute can be used with many HTML+ elements to facilitate
automatic generation of a conventional looking index, see section 13.

Implicit links are useful when you want to reuse a given subdocument in
another independent book, and for non-HTML+ formats such as scanned
page images. To define implicit links, you need to first create a HTML+
document such as a table of contents, and to make each entry into a
hypertext link using the <A> element with the attribute
REL="SUBDOCUMENT". When the user follows one of these links, the
browser scans the current document to locate the next <A> element with
the subdocument relationship. If it reaches the end of the document it
looks for a LINK element with REL=NEXT. This procedure is used to imply
a LINK element in the retrieved subdocument. A similar process is used
to imply a LINK element with REL=PREVIOUS. The other links for the
current document are simply inherited, i.e. any bookmarks, glossary or
index links that hold for the table of contents, also hold for the
subdocument.

The browser then retrieves the subdocument and merges the implied LINKs
with any that are given explicitly. If the user now presses the "Next"
button on the toolbar (or menu), the browser follows the implicit link
to the next subdocument. The browser needs to look again at the parent
document to find the new next subdocument. This mechanism is difficult
to explain, but simple to write documents for. All that authors need to
do, is to remember to include the subdocument relationship when
defining hypertext links.

For  a hundred page scanned document where each page is held as a
separate file, the "table of contents" is going to be pretty dull, and
there is little point creating it as an HTML+ node. Instead, you should
use an HTTP server which passes the missing LINK elements as header
fields for each page image. The suggested representation for these
header fields uses the same  attributes and syntax as the LINK element:

    WWW-Link: REL="Next" HREF="http://info.cern.ch/...."


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There  could be several WWW-Link: headers, one for each implied LINK.
This idea puts the burden on the server to supply such links as
appropriate to each requested document. 

16  Acknowledgements

I  would like to thank the many people on the www-talk mailing list who
have contributed to the design of HTML+ and to the management of HP
Labs for their support during this work.

David  Raggett, Hewlett Packard Laboratories, October 1993.

17  References

  "Hypertext Markup Language (HTML)", Tim Berners-Lee, January 1993.
      URL=ftp://info.cern.ch/pub/www/doc/html-spec.ps
      or http://info.cern.ch/hypertext/WWW/MarkUp/MarkUp.html

  "Uniform Resource Locators", Tim Berners-Lee, January 1992.
      URL=ftp://info.cern.ch/pub/www/doc/url7a.ps
      or http://info.cern.ch/hypertext/WWW/Addressing/Addressing.html

  "Protocol for the Retrieval and Manipulation of Texual and Hypermedia
   Information",
      Tim Berners-Lee, 1993.
      URL=ftp://info.cern.ch/pub/www/doc/http-spec.ps
      or http://info.cern.ch/hypertext/WWW/Protocols/HTTP/HTTP2.html

   "The SGML Handbook", Charles F. GoldFarb, pub. 1990 by the Clarendon
    Press, Oxford.


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                                   Appendix I
        ==========

    The HTML+ Document Type Definition (DTD). The prelim-
    inaries are taken from the HTML DTD and declares the 
    character set as Latin-1, disables markup minimisation 
    and sets limits for tag/attribute names to 34 characters, 
    and attribute values to a maximum of 1024 characters.

<!SGML  "ISO 8879:1986" -- Document Type Definition for the HyperText
Markup Language Plus  for use with the World Wide Web application
(HTML+ DTD). These initial settings are take from the HTML DTD.

        NOTE: This is a definition of HTML with respect to
        SGML, and assumes an understanding of SGML terms.
--  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  95  32
              255   1  UNUSED

CAPACITY  SGMLREF
              TOTALCAP        150000
              GRPCAP          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 31 127 255
       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


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       DELIM    GENERAL  SGMLREF
                SHORTREF SGMLREF
       NAMES    SGMLREF
       QUANTITY SGMLREF
                NAMELEN  34
                TAGLVL   100
                LITLEN   1024
                GRPGTCNT 150
                GRPCNT   64

FEATURES 
  MINIMIZE
    DATATAG  NO
    OMITTAG  NO
    RANK     NO
    SHORTTAG NO
  LINK
    SIMPLE   NO
    IMPLICIT NO
    EXPLICIT NO
  OTHER
    CONCUR  NO
    SUBDOC  NO
    FORMAL  YES
  APPINFO NONE
> 
<!DOCTYPE HTMLPLUS [
<!-- DTD for HTML+ 
Markup minimisation should be avoided, otherwise the default <!SGML>
declaration is fine. Browsers should be forgiving of markup errors.

Common Attributes:

id      the id attribute allows authors to name elements such as headers 
        and paragraphs as potential destinations for links. Note that 
        links don't specify points, but rather extended objects.
index   allows authors to specify how given headers etc should be 
        indexed as primary or secondary keys, where "/" separates primary 
        from secondary keys, ";" separates multiple entries
-->
<!-- ENTITY DECLARATIONS
 <!ENTITY % foo "X | Y | Z"> is a macro definition for parameters and
 in subsequent statements, the string "%foo;" is expanded to "X | Y | Z"

 Various classes of SGML text types:

  #CDATA  text which doesn't include markup or entity references
  #RCDATA text with entity references but no markup
  #PCDATA text occurring in a context in which markup and entity
     references may occur.
-->


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<!ENTITY % URL "CDATA" -- a URL or URN designating a hypertext node -->
<!ENTITY % emph1 "I|B|U|S|SUP|SUB|TT">
<!ENTITY % emph2 "Q|CITE|PERSON|ACRONYM|ABBREV|EM|STRONG">
<!ENTITY % emph3 "CMD|ARG|KBD|VAR|DFN|CODE|SAMP|REMOVED|ADDED">
<!ENTITY % emph "%emph1;|%emph2;|%emph3;">
<!ENTITY % misc "RENDER|FOOTNOTE|MARGIN|INPUT|TEXTAREA|SELECT">
<!ENTITY % text "#PCDATA|A|IMG|IMAGE|%emph;|%misc;|BR|CHANGED">
<!ENTITY % paras "P|PRE|LIT|FIG">
<!ENTITY % lists "UL|OL|DL|MENU|DIR">
<!ENTITY % block "TABLE|FORM|MATH|NOTE|QUOTE|ABSTRACT|BYLINE|HR">
<!ENTITY % heading "H1|H2|H3|H4|H5|H6"> 
<!ENTITY % table "%text;|P|%heading;|%lists;">
<!ENTITY % math "BOX|%text;">
<!ENTITY % main "%heading;|%block;|%lists;|%paras;|%text;">
<!ENTITY % setup "(TITLE? & ISINDEX? & NEXTID? & LINK* & BASE?)">

<!-- Basic types of elements:
  <!ELEMENT tagname - - CONTENT> elements needing end tags
  <!ELEMENT tagname - O CONTENT> elements with optional end tags
  <!ELEMENT tagname - O EMPTY> elements without content or end tags

The content definition is:
       -  an entity definition as defined above
       -  a tagname
       -  (brackets enclosing the above)
These may be combined with the operators:
  A*      A occurs zero or more times
  A+      A occurs one or more times
  A|B     implies either A or B
  A?      A occurs zero or one times
  A,B     implies first A then B
  A&B     either or both A and B (in either order)
-->

<!ELEMENT HTMLPLUS O O ((HEAD, BODY) | ((%setup;), (%main;)*))>
<!ATTLIST HTMLPLUS
        version CDATA #IMPLIED -- the HTML+ version number --
        forms   (on|off) on    -- used to disable form filling -->

<!ELEMENT HEAD - - (%setup;) -- delimits document wide properties -->
<!ELEMENT BODY - - (%main;)* -- delimits the document's body -->

<!-- Document title -->
<!ELEMENT TITLE - - (#PCDATA | %emph;)+>
<!ATTLIST TITLE
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!-- Document headers -->
<!ELEMENT (%heading;) - - (#PCDATA | %emph;)+>


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<!ATTLIST (%heading;)
        id      ID      #IMPLIED -- defines link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!-- character emphasis -->
<!ELEMENT (%emph;) - - (%text;)*>
<!ATTLIST (%emph;)
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT (FOOTNOTE|MARGIN) - - (%text;)* -(FOOTNOTE|MARGIN)>
<!ATTLIST (FOOTNOTE|MARGIN)
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT RENDER -O (EMPTY) -- how to render unknown elements -->
<!ATTLIST RENDER
        tag     CDATA   #IMPLIED -- tag name --
        style   CDATA   #IMPLIED -- comma separated list of styles -->

<!-- Paragraphs which act as containers for the following text -->
<!ELEMENT P - O (L|%text;)+>
<!ATTLIST P
        id      ID      #IMPLIED -- link destination --
        align   (left|indent|center|right|justify) left
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->
<!ELEMENT L - O (%text;)+>
<!ATTLIST L
        id      ID      #IMPLIED -- link destination --
        align   (left|indent|center|right|justify) left
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT HR - O EMPTY -- Horizontal Rule -->
<!ELEMENT BR - O EMPTY -- line break in normal text-->

<!ELEMENT PRE - - (TAB|%text;)+ -- preformatted fixed pitch text -->
<!ATTLIST PRE
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT LIT - - (TAB|%text;)+ -- literal variable pitch text -->
<!ATTLIST LIT
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->


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<!ELEMENT TAB - O EMPTY -- tabs for imported text -->
<!ATTLIST TAB
        at      NUMBER  #IMPLIED -- measured in widths of an M --
        align   (left|center|right|decimal) left -- tab alignment -->

<!ELEMENT QUOTE - - (P|%text;)* -- block quote -->
<!ATTLIST QUOTE
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT ABSTRACT - - (P|%text;)* -- document summary -->
<!ATTLIST ABSTRACT
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->
<!ELEMENT BYLINE - - (P|%text;)* -- info on author -->
<!ATTLIST BYLINE
        id      ID      #IMPLIED -- link destination --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->
<!ELEMENT NOTE - - (P|%text;)* -- admonishment -->
<!ATTLIST NOTE
        id      ID      #IMPLIED -- link destination --
        role    CDATA   #IMPLIED -- eg Tip, Note, Warning, or Error --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT (ADDRESS|BLOCKQUOTE) - - (%text;|P)* -- needed by HTML -->

<!-- Lists which can be nested -->
<!ELEMENT OL - - (LI | UL | OL)+ -- ordered list -->
<!ATTLIST OL
        id      ID      #IMPLIED
        compact (compact)       #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->
<!ELEMENT UL - - (LI | UL | OL)+ -- unordered list -->
<!ATTLIST UL
        id      ID      #IMPLIED    -- link destination --
        compact (compact) #IMPLIED  -- reduced interitem spacing --
        plain   (plain) #IMPLIED -- suppress bullets --
        wrap    (vert|horiz) vert -- multicolumn list wrap style --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!-- List items for UL and OL lists -->
<!ELEMENT LI - O (DL|P|%text;)+>
<!ATTLIST LI
        id      ID      #IMPLIED


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        src     %URL;   #IMPLIED -- icon for use in place of bullet --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT MENU - - (LI)* -- plain single column list -->
<!ATTLIST MENU
        id      ID      #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->
<!ELEMENT DIR - - (LI)* -- plain multi column list -->
<!ATTLIST DIR
        id      ID      #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!-- Definition Lists (terms + definitions) -->
<!ELEMENT DL - - (DT+,DD)+>
<!ATTLIST DL
        id      ID      #IMPLIED
        compact (compact)       #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT DT - O (%text;)+ -- term text -- >
<!ELEMENT DD - O (P|UL|OL|DL|%text;)+ -- definition text -- >
<!ATTLIST (DT|DD)
        id      ID      #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT CAPTION - - (%text;)+ -- table or figure caption -->
<!ATTLIST CAPTION
        id      ID      #IMPLIED
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT TABLE - - (CAPTION?, (TH|TD|TR)*) -- mixed headers & data -->
<!ATTLIST TABLE
        id      ID      #IMPLIED
        border (border) #IMPLIED -- draw borders --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT TH - O (%table;)* -- a header cell -->
<!ATTLIST TH
        colspan NUMBER    1     -- columns spanned --
        rowspan NUMBER    1     --. rows spanned --
        align   (left|center|right) center -- alignment in cell --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->
<!ELEMENT TD - O (%table;)* -- a data cell -->
<!ATTLIST TD


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        colspan NUMBER    1     -- columns spanned --
        rowspan NUMBER    1     --. rows spanned --
        align   (left|center|right) center -- alignment in cell --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->
<!ELEMENT TR - O (EMPTY) -- row separator -->
<!ATTLIST TR id ID #IMPLIED>

<!ELEMENT FORM - - (MH, (%main;)*) -(FORM) -- forms can't be nested -->
<!ATTLIST FORM
        id      ID      #IMPLIED
        action  %URL;   #IMPLIED -- defaults for URL for current doc --
        method  CDATA   #IMPLIED -- PUT, POST, DELETE etc. --
        lang    CDATA   #IMPLIED -- ISO language abbreviation --
        index   CDATA   #IMPLIED -- entries for index compilation -->

<!ELEMENT MH - - CDATA -- one or more RFC 822 header fields -->
<!ATTLIST MH hidden (hidden) #IMPLIED -- hide mail headers from view -->

<!ELEMENT INPUT - O EMPTY>
<!ATTLIST INPUT
        name    CDATA   #IMPLIED -- attribute name --
        type    CDATA   #IMPLIED -- a wide variety of field types --
        size    CDATA   #IMPLIED -- visible size of text fields --
        min     NUMBER  #IMPLIED -- for range controls --
        max     NUMBER  #IMPLIED -- for range controls or text fields --
        value   CDATA   #IMPLIED -- attribute value (altered by user) --
        checked (checked) #IMPLIED -- check boxes and radio buttons --
        disabled (disabled) #IMPLIED -- if grayed out --
        error   (error) #IMPLIED -- if in error --
        src      %URL;  #IMPLIED -- for certain fields e.g. IMAGEs --
        align (top|middle|bottom) top -- for IMAGE fields only --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->

<!ELEMENT TEXTAREA - - CDATA -- multi-line text fields -->
<!ATTLIST TEXTAREA
        name    CDATA   #IMPLIED -- attribute name --
        cols    NUMBER  #IMPLIED -- visible width in characters --
        rows    NUMBER  #IMPLIED -- visible height in characters --
        disabled (disabled) #IMPLIED -- if grayed out --
        error   (error) #IMPLIED -- if in error --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->

<!ELEMENT SELECT - - (OPTION+) -- combo style selection lists -->
<!ATTLIST SELECT
        name    CDATA   #IMPLIED -- attribute name --
        several (several) #IMPLIED -- permits multiple selections --
        error   (error) #IMPLIED -- if in error --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->

<!ELEMENT OPTION - - CDATA>
<!ATTLIST OPTION


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        selected (selected) #IMPLIED -- if initially selected --
        disabled (disabled) #IMPLIED -- if grayed out --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->

<!ELEMENT FIG - - (CAPTION?,(%text;)*)>
<!ATTLIST FIG
        id      ID      #IMPLIED
        align   (left|center|right|float) float -- position --
        ismap   (ismap) #IMPLIED -- server handles mouse clicks/drags --
        src     %URL;   #IMPLIED -- link to image data --
        index   CDATA   #IMPLIED -- entries for index compilation --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->
<!ELEMENT IMG - O EMPTY>
<!ATTLIST IMG
        src     %URL;   #REQUIRED -- where to get image data --
        align   (top|middle|bottom) top  -- top, middle or bottom --
        seethru CDATA   #IMPLIED  -- for chromakey --
        alt     CDATA   #IMPLIED -- description for text-only displays--
        ismap   (ismap) #IMPLIED -- send mouse clicks/drags to server-->
<!ELEMENT IMAGE - - (A|%text;)*>
<!ATTLIST IMAGE
        src     %URL;   #REQUIRED -- where to get image data --
        align   (top|middle|bottom) top  -- top, middle or bottom --
        seethru CDATA   #IMPLIED -- for transparency --
        ismap   (ismap) #IMPLIED -- send mouse clicks/drags to server--
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->

<!-- proposal for representing formulae -->
<!ELEMENT MATH - - (%math;)*>
<!ATTLIST MATH id ID #IMPLIED>
<!ELEMENT BOX - - ((%math;)*, OVER?, (%math;)*)>
<!ELEMENT OVER - O EMPTY>

<!ELEMENT CHANGED - O EMPTY -- for change bars -->
<!ATTLIST CHANGED -- one of id and idref is always required --
        id      ID      #IMPLIED -- signals start of changes --
        idref   IDREF   #IMPLIED -- signals end of changes -->

<!-- Hypertext Links from points within document nodes -->
<!ELEMENT A - - (#PCDATA | IMG | EM | EMBED)*>
<!ATTLIST A
        id      ID      #IMPLIED -- as target of link --
        name    CDATA   #IMPLIED -- needed by HTML--
        shape   CDATA   #IMPLIED -- points for shaped buttons --
        href    %URL;   #IMPLIED -- destination node --
        rel     CDATA   #IMPLIED -- forward relationship type --
        rev     CDATA   #IMPLIED -- reverse relationship type --
        methods CDATA   #IMPLIED -- supported public methods --
        effect  CDATA   #IMPLIED -- replace/new/overlay/embed --
        print   CDATA   #IMPLIED -- reference/footnote/section --
        title   CDATA   #IMPLIED -- when otherwise unavailable --


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        type    CDATA   #IMPLIED -- for presentation cues --
        size    NAMES   #IMPLIED -- for progress cues --
        lang    CDATA   #IMPLIED -- ISO language abbreviation -->
<!-- Other kinds of relationships between documents -->
<!ELEMENT LINK - O EMPTY>

<!ATTLIST LINK
        idref  IDREF    #IMPLIED -- starting point --
        href    %URL;   #IMPLIED -- destination node --
        rel    CDATA    #IMPLIED -- forward relationship type --
        rev    CDATA    #IMPLIED -- reverse relationship type --
        methods CDATA   #IMPLIED -- supported public methods -->

<!-- Original document URL for resolving relative URLs  -->
<!ELEMENT BASE - O EMPTY>
<!ATTLIST BASE HREF %URL; #IMPLIED>

<!-- Signifies the document's URL accepts queries -->
<!ELEMENT ISINDEX - O (EMPTY)>
<!ATTLIST ISINDEX href %URL; #IMPLIED
      -- defaults to document's URL -->

<!-- For use with autonumbering editors - don't reuse ids,
     allocate next one starting from this one -->
<!ELEMENT NEXTID - O (EMPTY)>
<!ATTLIST NEXTID N NAME #REQUIRED>

<!-- Mnemonic character entities for 8 bit ANSI Latin-1 
     ignore when using other character sets -->
<!ENTITY iexcl "&#161;" -- inverted exclamation mark -->
<!ENTITY cent "&#161;" -- cent sign -->
<!ENTITY pound "&#163;" -- pound sign -->
<!ENTITY yen "&#165;" -- yen sign -->
<!ENTITY brvbar "&#166;" -- broken vertical bar -->
<!ENTITY sect "&#167;" -- section sign -->
<!ENTITY copy "&#169;" -- copyright sign -->
<!ENTITY laquo "&#171;" -- angle quotation mark, left -->
<!ENTITY raquo "&#187;" -- angle quotation mark, right -->
<!ENTITY not "&#172;" -- negation sign -->
<!ENTITY reg "&#174;" -- circled R registered sign -->
<!ENTITY deg "&#176;" -- degree sign -->
<!ENTITY plusmn "&#177;" -- plus or minus sign -->
<!ENTITY sup2 "&#178;" -- superscript 2 -->
<!ENTITY sup3 "&#179;" -- superscript 3 -->
<!ENTITY micro "&#181;" -- micro sign -->
<!ENTITY para "&#182;" -- paragraph sign -->
<!ENTITY sup1 "&#185;" -- superscript 1 -->
<!ENTITY middot "&#183;" -- center dot -->
<!ENTITY frac14 "&#188;" -- fraction 1/4 -->
<!ENTITY frac12 "&#189;" -- fraction 1/2 -->
<!ENTITY iquest "&#191;" -- inverted question mark -->


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<!ENTITY frac34 "&#190;" -- fraction 3/4 -->
<!ENTITY AElig "&#198;" -- capital AE diphthong (ligature) -->
<!ENTITY Aacute "&#193;" -- capital A, acute accent -->
<!ENTITY Acirc "&#194;" -- capital A, circumflex accent -->
<!ENTITY Agrave "&#192;" -- capital A, grave accent -->
<!ENTITY Aring "&#197;" -- capital A, ring -->
<!ENTITY Atilde "&#195;" -- capital A, tilde -->
<!ENTITY Auml "&#196;" -- capital A, dieresis or umlaut mark -->
<!ENTITY Ccedil "&#199;" -- capital C, cedilla -->
<!ENTITY ETH "&#208;" -- capital Eth, Icelandic -->
<!ENTITY Eacute "&#201;" -- capital E, acute accent -->
<!ENTITY Ecirc "&#202;" -- capital E, circumflex accent -->
<!ENTITY Egrave "&#200;" -- capital E, grave accent -->
<!ENTITY Euml "&#203;" -- capital E, dieresis or umlaut mark -->
<!ENTITY Iacute "&#205;" -- capital I, acute accent -->
<!ENTITY Icirc "&#206;" -- capital I, circumflex accent -->
<!ENTITY Igrave "&#204;" -- capital I, grave accent -->
<!ENTITY Iuml "&#207;" -- capital I, dieresis or umlaut mark -->
<!ENTITY Ntilde "&#209;" -- capital N, tilde -->
<!ENTITY Oacute "&#211;" -- capital O, acute accent -->
<!ENTITY Ocirc "&#212;" -- capital O, circumflex accent -->
<!ENTITY Ograve "&#210;" -- capital O, grave accent -->
<!ENTITY Oslash "&#216;" -- capital O, slash -->
<!ENTITY Otilde "&#213;" -- capital O, tilde -->
<!ENTITY Ouml "&#214;" -- capital O, dieresis or umlaut mark -->
<!ENTITY THORN "&#222;" -- capital THORN, Icelandic -->
<!ENTITY Uacute "&#218;" -- capital U, acute accent -->
<!ENTITY Ucirc "&#219;" -- capital U, circumflex accent -->
<!ENTITY Ugrave "&#217;" -- capital U, grave accent -->
<!ENTITY Uuml "&#220;" -- capital U, dieresis or umlaut mark -->
<!ENTITY Yacute "&#221;" -- capital Y, acute accent -->
<!ENTITY aacute "&#225;" -- small a, acute accent -->
<!ENTITY acirc "&#226;" -- small a, circumflex accent -->
<!ENTITY aelig "&#230;" -- small ae diphthong (ligature) -->
<!ENTITY agrave "&#224;" -- small a, grave accent -->
<!ENTITY amp "&amp;" -- ampersand -->
<!ENTITY aring "&#229;" -- small a, ring -->
<!ENTITY atilde "&#227;" -- small a, tilde -->
<!ENTITY auml "&#228;" -- small a, dieresis or umlaut mark -->
<!ENTITY ccedil "&#231;" -- small c, cedilla -->
<!ENTITY eacute "&#233;" -- small e, acute accent -->
<!ENTITY ecirc "&#234;" -- small e, circumflex accent -->
<!ENTITY egrave "&#232;" -- small e, grave accent -->
<!ENTITY eth "&#240;" -- small eth, Icelandic -->
<!ENTITY euml "&#235;" -- small e, dieresis or umlaut mark -->
<!ENTITY gt "&#62;" -- greater than -->
<!ENTITY iacute "&#237;" -- small i, acute accent -->
<!ENTITY icirc "&#238;" -- small i, circumflex accent -->
<!ENTITY igrave "&#236;" -- small i, grave accent -->
<!ENTITY iuml "&#239;" -- small i, dieresis or umlaut mark -->
<!ENTITY lt "&lt;" -- less than -->


Internet Draft                     55                      November 1993
HTML+ Document Format                                            Raggett


<!ENTITY ntilde "&#241;" -- small n, tilde -->
<!ENTITY oacute "&#243;" -- small o, acute accent -->
<!ENTITY ocirc "&#244;" -- small o, circumflex accent -->
<!ENTITY ograve "&#242;" -- small o, grave accent -->
<!ENTITY oslash "&#248;" -- small o, slash -->
<!ENTITY otilde "&#245;" -- small o, tilde -->
<!ENTITY ouml "&#246;" -- small o, dieresis or umlaut mark -->
<!ENTITY szlig "&#223;" -- small sharp s, German (sz ligature) -->
<!ENTITY thorn "&#254;" -- small thorn, Icelandic -->
<!ENTITY uacute "&#250;" -- small u, acute accent -->
<!ENTITY ucirc "&#251;" -- small u, circumflex accent -->
<!ENTITY ugrave "&#249;" -- small u, grave accent -->
<!ENTITY uuml "&#252;" -- small u, dieresis or umlaut mark -->
<!ENTITY yacute "&#253;" -- small y, acute accent -->
<!ENTITY yuml "&#255;" -- small y, dieresis or umlaut mark -->

<!-- The END -->
]>


Internet Draft                     56                      November 1993
HTML+ Document Format                                            Raggett


                              Appendix  II

The  proposed character entities for HTML+ and their corresponding
character codes for Unicode and the Adobe Latin-1 & Symbol
character sets.

[this table is only available in the <draft-raggett-www-html-00.ps>
version]

Many  thanks to Bob Stayton for volunteering his time and effort to
prepare this table.


Internet Draft                     57                      November 1993
HTML+ Document Format                                            Raggett


                             Appendix  III

ANSI  C Code for testing if a point lies within a polygon.  This may be
freely used provided the original copyright  message is retained in
full.

/*  ** Reproduced with thanks from mapper 1.2 ** 7/26/93 Kevin Hughes,
kevinh@pulua.hcc.hawaii.edu ** polygon code copyright 1992 by Eric
Haines, erich@eye.com */

#include  <stdio.h>

#define  MAXLINE 500 #define MAXVERTS 100

#define  X 0 #define Y 1

int  pointinpoly(double point[2], double pgon[MAXVERTS][2]) {
    int i, numverts, inside_flag, xflag0;
    int crossings;
    double *p, *stop;
    double tx, ty, y;

    for (i = 0; pgon[i][X] != -1 && i < MAXVERTS; i++)
            ;
    numverts = i;
    crossings = 0;

    tx = point[X];
    ty = point[Y];
    y = pgon[numverts - 1][Y];

    p = (double *) pgon + 1;
    if ((y >= ty) != (*p >= ty))
    {
        if ((xflag0 = (pgon[numverts - 1][X] >= tx)) ==
            (*(double *) pgon >= tx))
        {
            if (xflag0)
                crossings++;
        }
         else
        {
            crossings += (pgon[numverts - 1][X] - (y - ty) *
                        (*(double *) pgon - pgon[numverts - 1][X]) /
                        (*p - y)) >= tx;
        }
    }

    stop = pgon[numverts];

    for (y = *p, p += 2; p < stop; y = *p, p += 2)


Internet Draft                     58                      November 1993
HTML+ Document Format                                            Raggett


    {
        if (y >= ty)
        {
            while ((p < stop) && (*p >= ty))
                p += 2;
            if (p >= stop)
                break;
            if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
            {
                if (xflag0)
                    crossings++;
            }
            else
            {
                crossings += (*(p - 3) - (*(p - 2) - ty) *
                   (*(p - 1) - *(p - 3)) / (*p - *(p - 2))) >= tx;
            }
        }
        else
        {
            while ((p < stop) && (*p < ty))
                p += 2;
            if (p >= stop)
                break;
            if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
            {
                if (xflag0)
                    crossings++;
            }
            else
            {
                crossings += (*(p - 3) - (*(p - 2) - ty) *
                   (*(p - 1) - *(p - 3)) / (*p - *(p - 2))) >= tx;
            }
        }
    }
    inside_flag = crossings & 0x01;
    return (inside_flag);
} 


Internet Draft                     59                      November 1993
HTML+ Document Format                                            Raggett


                                  Appendix IV
        ===========

    Alphabetically sorted list of HTML+ tags and their
    associated attribute names.

    A               id, name, shape, href, rel, rev, methods,
                    effect, print, title, type, size, lang
    ABBREV          id, lang, index
    ABSTRACT        id, lang, index
    ACRONYM         id, lang, index
    ADDED           id, lang, index
    ADDRESS
    ARG             id, lang, index
    B               id, lang, index
    BASE            href
    BLOCKQUOTE
    BODY
    BOX
    BR
    BYLINE          id, lang, index
    CAPTION         id, lang, index
    CHANGED         id, idref
    CITE            id, lang, index
    CMD             id, lang, index
    CODE            id, lang, index
    DD              id, lang, index
    DFN             id, lang, index
    DIR             id, lang, index
    DL              id, compact, lang, index
    DT              id, lang, index
    EM              id, lang, index
    FIG             id, align, ismap, src, index, lang
    FOOTNOTE        id, lang, index
    FORM            id, action, method, lang, index
    H1              id, lang, index
    H2              id, lang, index
    H3              id, lang, index
    H4              id, lang, index
    H5              id, lang, index
    H6              id, lang, index
    HEAD
    HTMLPLUS        version, forms
    I               id, lang, index
    IMAGE           src, align, seethru, ismap, lang
    IMG             src, align, seethru, alt, ismap
    INPUT           name, type, size, min, max, value, checked,
                    disabled, error, src, align, lang
    ISINDEX         href
    KBD             id, lang, index
    L               id, align, lang, index


Internet Draft                     60                      November 1993
HTML+ Document Format                                            Raggett


    LI              id, src, lang, index
    LINK            idref, href, rel, rev, methods
    LIT             id, lang, index
    MARGIN          id, lang, index
    MATH            id
    MENU            id, lang, index
    NEXTID          n
    NOTE            id, role, lang, index
    OL              id, compact, lang, index
    OPTION          selected, disabled, lang
    OVER
    P               id, align, lang, index
    PERSON          id, lang, index
    PRE             id, lang, index
    Q               id, lang, index
    QUOTE           id, lang, index
    RENDER          tag, style
    REMOVED         id, lang, index
    S               id, lang, index
    SAMP            id, lang, index
    SELECT          name, several, error, lang
    STRONG          id, lang, index
    SUB             id, lang, index
    SUP             id, lang, index
    TAB             at, align
    TABLE           id, border, lang, index
    TD              colspan, rowspan, align, lang
    TEXTAREA        name, cols, rows, disabled, error, lang
    TH              colspan, rowspan, align, lang
    TITLE           id, lang, index
    TR              id
    TT              id, lang, index
    U               id, lang, index
    UL              id, compact, plain, wrap, lang, index
    VAR             id, lang, index


Internet Draft                     61                      November 1993
