tagset(3)

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 ele
ments 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::emp
tyElement{'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 ref
erence 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 doc
ument.
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 differ
ently 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 slav
ishly obey them, not the data tables in this document.

COPYRIGHT

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".

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