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 HTML::Tagset - data tables useful in parsing HTML


NAME

HTML::Tagset - data tables useful in parsing HTML


SYNOPSIS

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


DESCRIPTION

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.)

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

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

the HTML::Element manpage, the HTML::TreeBuilder manpage, the HTML::LinkExtor manpage


COPYRIGHT

Copyright 1995-2000 Gisle Aas; copyright 2000 Sean M. Burke.

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


AUTHOR

Current maintainer: Sean M. Burke, <sburke@cpan.org>

Most of the code/data in this module was adapted from code written by Gisle Aas <gisle@aas.no> for HTML::Element, HTML::TreeBuilder, and HTML::LinkExtor.

 HTML::Tagset - data tables useful in parsing HTML