HTML::Tagset - data tables useful in parsing HTML

HTML-Tagset documentation Contained in the HTML-Tagset distribution.

Index

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NAME

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HTML::Tagset - data tables useful in parsing HTML

VERSION

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Version 3.20

SYNOPSIS

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  use HTML::Tagset;
  # Then use any of the items in the HTML::Tagset package
  #  as need arises

DESCRIPTION

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This module contains several data tables useful in various kinds of HTML parsing operations.

Note that all tag names used are lowercase.

In the following documentation, a "hashset" is a hash being used as a set -- the hash conveys that its keys are there, and the actual values associated with the keys are not significant. (But what values are there, are always true.)

VARIABLES

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Note that none of these variables are exported.

hashset %HTML::Tagset::emptyElement

This hashset has as values the tag-names (GIs) of elements that cannot have content. (For example, "base", "br", "hr".) So $HTML::Tagset::emptyElement{'hr'} exists and is true. $HTML::Tagset::emptyElement{'dl'} does not exist, and so is not true.

hashset %HTML::Tagset::optionalEndTag

This hashset lists tag-names for elements that can have content, but whose end-tags are generally, "safely", omissible. Example: $HTML::Tagset::emptyElement{'li'} exists and is true.

hash %HTML::Tagset::linkElements

Values in this hash are tagnames for elements that might contain links, and the value for each is a reference to an array of the names of attributes whose values can be links.

hash %HTML::Tagset::boolean_attr

This hash (not hashset) lists what attributes of what elements can be printed without showing the value (for example, the "noshade" attribute of "hr" elements). For elements with only one such attribute, its value is simply that attribute name. For elements with many such attributes, the value is a reference to a hashset containing all such attributes.

hashset %HTML::Tagset::isPhraseMarkup

This hashset contains all phrasal-level elements.

hashset %HTML::Tagset::is_Possible_Strict_P_Content

This hashset contains all phrasal-level elements that be content of a P element, for a strict model of HTML.

hashset %HTML::Tagset::isHeadElement

This hashset contains all elements that elements that should be present only in the 'head' element of an HTML document.

hashset %HTML::Tagset::isList

This hashset contains all elements that can contain "li" elements.

hashset %HTML::Tagset::isTableElement

This hashset contains all elements that are to be found only in/under a "table" element.

hashset %HTML::Tagset::isFormElement

This hashset contains all elements that are to be found only in/under a "form" element.

hashset %HTML::Tagset::isBodyMarkup

This hashset contains all elements that are to be found only in/under the "body" element of an HTML document.

hashset %HTML::Tagset::isHeadOrBodyElement

This hashset includes all elements that I notice can fall either in the head or in the body.

hashset %HTML::Tagset::isKnown

This hashset lists all known HTML elements.

hashset %HTML::Tagset::canTighten

This hashset lists elements that might have ignorable whitespace as children or siblings.

array @HTML::Tagset::p_closure_barriers

This array has a meaning that I have only seen a need for in HTML::TreeBuilder, but I include it here on the off chance that someone might find it of use:

When we see a "<p>" token, we go lookup up the lineage for a p element we might have to minimize. At first sight, we might say that if there's a p anywhere in the lineage of this new p, it should be closed. But that's wrong. Consider this document:

  <html>
    <head>
      <title>foo</title>
    </head>
    <body>
      <p>foo
        <table>
          <tr>
            <td>
               foo
               <p>bar
            </td>
          </tr>
        </table>
      </p>
    </body>
  </html>

The second p is quite legally inside a much higher p.

My formalization of the reason why this is legal, but this:

  <p>foo<p>bar</p></p>

isn't, is that something about the table constitutes a "barrier" to the application of the rule about what p must minimize.

So @HTML::Tagset::p_closure_barriers is the list of all such barrier-tags.

hashset %isCDATA_Parent

This hashset includes all elements whose content is CDATA.

CAVEATS

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You may find it useful to alter the behavior of modules (like HTML::Element or HTML::TreeBuilder) that use HTML::Tagset's data tables by altering the data tables themselves. You are welcome to try, but be careful; and be aware that different modules may or may react differently to the data tables being changed.

Note that it may be inappropriate to use these tables for producing HTML -- for example, %isHeadOrBodyElement lists the tagnames for all elements that can appear either in the head or in the body, such as "script". That doesn't mean that I am saying your code that produces HTML should feel free to put script elements in either place! If you are producing programs that spit out HTML, you should be intimately familiar with the DTDs for HTML or XHTML (available at http://www.w3.org/), and you should slavishly obey them, not the data tables in this document.

SEE ALSO

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HTML::Element, HTML::TreeBuilder, HTML::LinkExtor

COPYRIGHT & LICENSE

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Copyright 1995-2000 Gisle Aas.

Copyright 2000-2005 Sean M. Burke.

Copyright 2005-2008 Andy Lester.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

ACKNOWLEDGEMENTS

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Most of the code/data in this module was adapted from code written by Gisle Aas for HTML::Element, HTML::TreeBuilder, and HTML::LinkExtor. Then it was maintained by Sean M. Burke.

AUTHOR

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Current maintainer: Andy Lester, <andy at petdance.com>

BUGS

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Please report any bugs or feature requests to bug-html-tagset at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=HTML-Tagset. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

HTML-Tagset documentation Contained in the HTML-Tagset distribution. 
package HTML::Tagset;

use strict;


use vars qw( $VERSION );

$VERSION = '3.20';


use vars qw(
    $VERSION
    %emptyElement %optionalEndTag %linkElements %boolean_attr
    %isHeadElement %isBodyElement %isPhraseMarkup
    %is_Possible_Strict_P_Content
    %isHeadOrBodyElement
    %isList %isTableElement %isFormElement
    %isKnown %canTighten
    @p_closure_barriers
    %isCDATA_Parent
);


%emptyElement   = map {; $_ => 1 } qw(base link meta isindex
                                     img br hr wbr
                                     input area param
                                     embed bgsound spacer
                                     basefont col frame
                                     ~comment ~literal
                                     ~declaration ~pi
                                    );
# The "~"-initial names are for pseudo-elements used by HTML::Entities
#  and TreeBuilder


%optionalEndTag = map {; $_ => 1 } qw(p li dt dd); # option th tr td);


%linkElements =
(
 'a'       => ['href'],
 'applet'  => ['archive', 'codebase', 'code'],
 'area'    => ['href'],
 'base'    => ['href'],
 'bgsound' => ['src'],
 'blockquote' => ['cite'],
 'body'    => ['background'],
 'del'     => ['cite'],
 'embed'   => ['pluginspage', 'src'],
 'form'    => ['action'],
 'frame'   => ['src', 'longdesc'],
 'iframe'  => ['src', 'longdesc'],
 'ilayer'  => ['background'],
 'img'     => ['src', 'lowsrc', 'longdesc', 'usemap'],
 'input'   => ['src', 'usemap'],
 'ins'     => ['cite'],
 'isindex' => ['action'],
 'head'    => ['profile'],
 'layer'   => ['background', 'src'],
 'link'    => ['href'],
 'object'  => ['classid', 'codebase', 'data', 'archive', 'usemap'],
 'q'       => ['cite'],
 'script'  => ['src', 'for'],
 'table'   => ['background'],
 'td'      => ['background'],
 'th'      => ['background'],
 'tr'      => ['background'],
 'xmp'     => ['href'],
);


%boolean_attr = (
# TODO: make these all hashes
  'area'   => 'nohref',
  'dir'    => 'compact',
  'dl'     => 'compact',
  'hr'     => 'noshade',
  'img'    => 'ismap',
  'input'  => { 'checked' => 1, 'readonly' => 1, 'disabled' => 1 },
  'menu'   => 'compact',
  'ol'     => 'compact',
  'option' => 'selected',
  'select' => 'multiple',
  'td'     => 'nowrap',
  'th'     => 'nowrap',
  'ul'     => 'compact',
);

#==========================================================================
# List of all elements from Extensible HTML version 1.0 Transitional DTD:
#
#   a abbr acronym address applet area b base basefont bdo big
#   blockquote body br button caption center cite code col colgroup
#   dd del dfn dir div dl dt em fieldset font form h1 h2 h3 h4 h5 h6
#   head hr html i iframe img input ins isindex kbd label legend li
#   link map menu meta noframes noscript object ol optgroup option p
#   param pre q s samp script select small span strike strong style
#   sub sup table tbody td textarea tfoot th thead title tr tt u ul
#   var
#
# Varia from Mozilla source internal table of tags:
#   Implemented:
#     xmp listing wbr nobr frame frameset noframes ilayer
#     layer nolayer spacer embed multicol
#   But these are unimplemented:
#     sound??  keygen??  server??
# Also seen here and there:
#     marquee??  app??  (both unimplemented)
#==========================================================================


%isPhraseMarkup = map {; $_ => 1 } qw(
  span abbr acronym q sub sup
  cite code em kbd samp strong var dfn strike
  b i u s tt small big 
  a img br
  wbr nobr blink
  font basefont bdo
  spacer embed noembed
);  # had: center, hr, table



%is_Possible_Strict_P_Content = (
 %isPhraseMarkup,
 %isFormElement,
 map {; $_ => 1} qw( object script map )
  # I've no idea why there's these latter exceptions.
  # I'm just following the HTML4.01 DTD.
);

#from html4 strict:
#<!ENTITY % fontstyle "TT | I | B | BIG | SMALL">
#
#<!ENTITY % phrase "EM | STRONG | DFN | CODE |
#                   SAMP | KBD | VAR | CITE | ABBR | ACRONYM" >
#
#<!ENTITY % special
#   "A | IMG | OBJECT | BR | SCRIPT | MAP | Q | SUB | SUP | SPAN | BDO">
#
#<!ENTITY % formctrl "INPUT | SELECT | TEXTAREA | LABEL | BUTTON">
#
#<!-- %inline; covers inline or "text-level" elements -->
#<!ENTITY % inline "#PCDATA | %fontstyle; | %phrase; | %special; | %formctrl;">


%isHeadElement = map {; $_ => 1 }
 qw(title base link meta isindex script style object bgsound);


%isList         = map {; $_ => 1 } qw(ul ol dir menu);


%isTableElement = map {; $_ => 1 }
 qw(tr td th thead tbody tfoot caption col colgroup);


%isFormElement  = map {; $_ => 1 }
 qw(input select option optgroup textarea button label);


%isBodyElement = map {; $_ => 1 } qw(
  h1 h2 h3 h4 h5 h6
  p div pre plaintext address blockquote
  xmp listing
  center

  multicol
  iframe ilayer nolayer
  bgsound

  hr
  ol ul dir menu li
  dl dt dd
  ins del
  
  fieldset legend
  
  map area
  applet param object
  isindex script noscript
  table
  center
  form
 ),
 keys %isFormElement,
 keys %isPhraseMarkup,   # And everything phrasal
 keys %isTableElement,
;



%isHeadOrBodyElement = map {; $_ => 1 }
  qw(script isindex style object map area param noscript bgsound);
  # i.e., if we find 'script' in the 'body' or the 'head', don't freak out.



%isKnown = (%isHeadElement, %isBodyElement,
  map{; $_=>1 }
   qw( head body html
       frame frameset noframes
       ~comment ~pi ~directive ~literal
));
 # that should be all known tags ever ever



%canTighten = %isKnown;
delete @canTighten{
  keys(%isPhraseMarkup), 'input', 'select',
  'xmp', 'listing', 'plaintext', 'pre',
};
  # xmp, listing, plaintext, and pre  are untightenable, and
  #   in a really special way.
@canTighten{'hr','br'} = (1,1);
 # exceptional 'phrasal' things that ARE subject to tightening.

# The one case where I can think of my tightening rules failing is:
#  <p>foo bar<center> <em>baz quux</em> ...
#                    ^-- that would get deleted.
# But that's pretty gruesome code anyhow.  You gets what you pays for.

#==========================================================================


@p_closure_barriers = qw(
  li blockquote
  ul ol menu dir
  dl dt dd
  td th tr table caption
  div
 );

# In an ideal world (i.e., XHTML) we wouldn't have to bother with any of this
# monkey business of barriers to minimization!


%isCDATA_Parent = map {; $_ => 1 }
  qw(script style  xmp listing plaintext);

# TODO: there's nothing else that takes CDATA children, right?

# As the HTML3 DTD (Raggett 1995-04-24) noted:
#   The XMP, LISTING and PLAINTEXT tags are incompatible with SGML
#   and derive from very early versions of HTML. They require non-
#   standard parsers and will cause problems for processing
#   documents with standard SGML tools.



1;