[OpenSPARC-T2-DV] / tools / perl-5.8.0 / lib / site_perl / 5.8.0 / HTML / Tagset.pm


require 5;
package HTML::Tagset;   # Time-stamp: "2000-10-20 19:35:06 MDT"
use strict;
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
);

$VERSION = '3.03';

=head1 NAME

HTML::Tagset - data tables useful in parsing HTML

=head1 SYNOPSIS

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

=head1 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.)

=over

=item 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
C<$HTML::Tagset::emptyElement{'hr'}> exists and is true.
C<$HTML::Tagset::emptyElement{'dl'}> does not exist, and so is not true.

=cut

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

%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

#---------------------------------------------------------------------------

=item hashset %HTML::Tagset::optionalEndTag

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

=cut

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

#---------------------------------------------------------------------------

=item 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.


=cut

%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'],
);

#---------------------------------------------------------------------------

=item 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.

=cut

%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)
#==========================================================================

=item hashset %HTML::Tagset::isPhraseMarkup

This hashset contains all phrasal-level elements.

=cut

%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


=item 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.

=cut

%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;">

=item hashset %HTML::Tagset::isHeadElement

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

=cut

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

=item hashset %HTML::Tagset::isList

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

=cut

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

=item hashset %HTML::Tagset::isTableElement

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

=cut

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

=item hashset %HTML::Tagset::isFormElement

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

=cut

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

=item hashset %HTML::Tagset::isBodyMarkup

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

=cut

%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,
;


=item hashset %HTML::Tagset::isHeadOrBodyElement

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

=cut

%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.


=item hashset %HTML::Tagset::isKnown

This hashset lists all known HTML elements.

=cut

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


=item hashset %HTML::Tagset::canTighten

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

=cut

%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.

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

=item array @HTML::Tagset::p_closure_barriers

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

When we see a "E<lt>pE<gt>" 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 C<@HTML::Tagset::p_closure_barriers> is the list of all such
barrier-tags.

=cut

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

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

###########################################################################

=item hashset %isCDATA_Parent

This hashset includes all elements whose content is CDATA.

=cut

%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.


###########################################################################

=back

=head1 CAVEATS

You may find it useful to alter the behavior of modules (like
C<HTML::Element> or C<HTML::TreeBuilder>) that use C<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 I<producing>
HTML -- for example, C<%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
I<intimately> familiar with the DTDs for HTML or XHTML (available at
C<http://www.w3.org/>), and you should slavishly obey them, not
the data tables in this document.

=head1 SEE ALSO

L<HTML::Element>, L<HTML::TreeBuilder>, L<HTML::LinkExtor>

=head1 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.

=head1 AUTHOR

Current maintainer: Sean M. Burke, E<lt>sburke@cpan.orgE<gt>

Most of the code/data in this module was adapted from code written by
Gisle Aas E<lt>gisle@aas.noE<gt> for C<HTML::Element>,
C<HTML::TreeBuilder>, and C<HTML::LinkExtor>.

=cut

1;
Commit	Line	Data
86530b38 AT	1
	2	require 5;
	3	package HTML::Tagset; # Time-stamp: "2000-10-20 19:35:06 MDT"
	4	use strict;
	5	use vars qw(
	6	$VERSION
	7	%emptyElement %optionalEndTag %linkElements %boolean_attr
	8	%isHeadElement %isBodyElement %isPhraseMarkup
	9	%is_Possible_Strict_P_Content
	10	%isHeadOrBodyElement
	11	%isList %isTableElement %isFormElement
	12	%isKnown %canTighten
	13	@p_closure_barriers
	14	%isCDATA_Parent
	15	);
	16
	17	$VERSION = '3.03';
	18
	19	=head1 NAME
	20
	21	HTML::Tagset - data tables useful in parsing HTML
	22
	23	=head1 SYNOPSIS
	24
	25	use HTML::Tagset;
	26	# Then use any of the items in the HTML::Tagset package
	27	# as need arises
	28
	29	=head1 DESCRIPTION
	30
	31	This module contains several data tables useful in various kinds of
	32	HTML parsing operations.
	33
	34	Note that all tag names used are lowercase.
	35
	36	In the following documentation, a "hashset" is a hash being used as a
	37	set -- the hash conveys that its keys are there, and the actual values
	38	associated with the keys are not significant. (But what values are
	39	there, are always true.)
	40
	41	=over
	42
	43	=item hashset %HTML::Tagset::emptyElement
	44
	45	This hashset has as values the tag-names (GIs) of elements that cannot
	46	have content. (For example, "base", "br", "hr".) So
	47	C<$HTML::Tagset::emptyElement{'hr'}> exists and is true.
	48	C<$HTML::Tagset::emptyElement{'dl'}> does not exist, and so is not true.
	49
	50	=cut
	51
	52	#==========================================================================
	53
	54	%emptyElement = map {; $_ => 1 } qw(base link meta isindex
	55	img br hr wbr
	56	input area param
	57	embed bgsound spacer
	58	basefont col frame
	59	~comment ~literal
	60	~declaration ~pi
	61	);
	62	# The "~"-initial names are for pseudo-elements used by HTML::Entities
	63	# and TreeBuilder
	64
65	#---------------------------------------------------------------------------
66
67	=item hashset %HTML::Tagset::optionalEndTag
68
69	This hashset lists tag-names for elements that can have content, but whose
70	end-tags are generally, "safely", omissible. Example:
71	C<$HTML::Tagset::emptyElement{'li'}> exists and is true.
72
73	=cut
74
75	%optionalEndTag = map {; $_ => 1 } qw(p li dt dd); # option th tr td);
76
77	#---------------------------------------------------------------------------
78
79	=item hash %HTML::Tagset::linkElements
80
81	Values in this hash are tagnames for elements that might contain
82	links, and the value for each is a reference to an array of the names
83	of attributes whose values can be links.
84
85
86	=cut
87
88	%linkElements =
89	(
90	'a' => ['href'],
91	'applet' => ['archive', 'codebase', 'code'],
92	'area' => ['href'],
93	'base' => ['href'],
94	'bgsound' => ['src'],
95	'blockquote' => ['cite'],
96	'body' => ['background'],
97	'del' => ['cite'],
98	'embed' => ['pluginspage', 'src'],
99	'form' => ['action'],
100	'frame' => ['src', 'longdesc'],
101	'iframe' => ['src', 'longdesc'],
102	'ilayer' => ['background'],
103	'img' => ['src', 'lowsrc', 'longdesc', 'usemap'],
104	'input' => ['src', 'usemap'],
105	'ins' => ['cite'],
106	'isindex' => ['action'],
107	'head' => ['profile'],
108	'layer' => ['background', 'src'],
109	'link' => ['href'],
110	'object' => ['classid', 'codebase', 'data', 'archive', 'usemap'],
111	'q' => ['cite'],
112	'script' => ['src', 'for'],
113	'table' => ['background'],
114	'td' => ['background'],
115	'th' => ['background'],
116	'tr' => ['background'],
117	'xmp' => ['href'],
118	);
119
120	#---------------------------------------------------------------------------
121
122	=item hash %HTML::Tagset::boolean_attr
123
124	This hash (not hashset) lists what attributes of what elements can be
125	printed without showing the value (for example, the "noshade" attribute
126	of "hr" elements). For elements with only one such attribute, its value
127	is simply that attribute name. For elements with many such attributes,
128	the value is a reference to a hashset containing all such attributes.
129
130	=cut
131
132	%boolean_attr = (
133	# TODO: make these all hashes
134	'area' => 'nohref',
135	'dir' => 'compact',
136	'dl' => 'compact',
137	'hr' => 'noshade',
138	'img' => 'ismap',
139	'input' => { 'checked' => 1, 'readonly' => 1, 'disabled' => 1 },
140	'menu' => 'compact',
141	'ol' => 'compact',
142	'option' => 'selected',
143	'select' => 'multiple',
144	'td' => 'nowrap',
145	'th' => 'nowrap',
146	'ul' => 'compact',
147	);
148
149	#==========================================================================
150	# List of all elements from Extensible HTML version 1.0 Transitional DTD:
151	#
152	# a abbr acronym address applet area b base basefont bdo big
153	# blockquote body br button caption center cite code col colgroup
154	# dd del dfn dir div dl dt em fieldset font form h1 h2 h3 h4 h5 h6
155	# head hr html i iframe img input ins isindex kbd label legend li
156	# link map menu meta noframes noscript object ol optgroup option p
157	# param pre q s samp script select small span strike strong style
158	# sub sup table tbody td textarea tfoot th thead title tr tt u ul
159	# var
160	#
161	# Varia from Mozilla source internal table of tags:
162	# Implemented:
163	# xmp listing wbr nobr frame frameset noframes ilayer
164	# layer nolayer spacer embed multicol
165	# But these are unimplemented:
166	# sound?? keygen?? server??
167	# Also seen here and there:
168	# marquee?? app?? (both unimplemented)
169	#==========================================================================
170
171	=item hashset %HTML::Tagset::isPhraseMarkup
172
173	This hashset contains all phrasal-level elements.
174
175	=cut
176
177	%isPhraseMarkup = map {; $_ => 1 } qw(
178	span abbr acronym q sub sup
179	cite code em kbd samp strong var dfn strike
180	b i u s tt small big
181	a img br
182	wbr nobr blink
183	font basefont bdo
184	spacer embed noembed
185	); # had: center, hr, table
186
187
188	=item hashset %HTML::Tagset::is_Possible_Strict_P_Content
189
190	This hashset contains all phrasal-level elements that be content of a
191	P element, for a strict model of HTML.
192
193	=cut
194
195	%is_Possible_Strict_P_Content = (
196	%isPhraseMarkup,
197	%isFormElement,
198	map {; $_ => 1} qw( object script map )
199	# I've no idea why there's these latter exceptions.
200	# I'm just following the HTML4.01 DTD.
201	);
202
203	#from html4 strict:
204	#<!ENTITY % fontstyle "TT \| I \| B \| BIG \| SMALL">
205	#
206	#<!ENTITY % phrase "EM \| STRONG \| DFN \| CODE \|
207	# SAMP \| KBD \| VAR \| CITE \| ABBR \| ACRONYM" >
208	#
209	#<!ENTITY % special
210	# "A \| IMG \| OBJECT \| BR \| SCRIPT \| MAP \| Q \| SUB \| SUP \| SPAN \| BDO">
211	#
212	#<!ENTITY % formctrl "INPUT \| SELECT \| TEXTAREA \| LABEL \| BUTTON">
213	#
214	#<!-- %inline; covers inline or "text-level" elements -->
215	#<!ENTITY % inline "#PCDATA \| %fontstyle; \| %phrase; \| %special; \| %formctrl;">
216
217	=item hashset %HTML::Tagset::isHeadElement
218
219	This hashset contains all elements that elements that should be
220	present only in the 'head' element of an HTML document.
221
222	=cut
223
224	%isHeadElement = map {; $_ => 1 }
225	qw(title base link meta isindex script style object bgsound);
226
227	=item hashset %HTML::Tagset::isList
228
229	This hashset contains all elements that can contain "li" elements.
230
231	=cut
232
233	%isList = map {; $_ => 1 } qw(ul ol dir menu);
234
235	=item hashset %HTML::Tagset::isTableElement
236
237	This hashset contains all elements that are to be found only in/under
238	a "table" element.
239
240	=cut
241
242	%isTableElement = map {; $_ => 1 }
243	qw(tr td th thead tbody tfoot caption col colgroup);
244
245	=item hashset %HTML::Tagset::isFormElement
246
247	This hashset contains all elements that are to be found only in/under
248	a "form" element.
249
250	=cut
251
252	%isFormElement = map {; $_ => 1 }
253	qw(input select option optgroup textarea button label);
254
255	=item hashset %HTML::Tagset::isBodyMarkup
256
257	This hashset contains all elements that are to be found only in/under
258	the "body" element of an HTML document.
259
260	=cut
261
262	%isBodyElement = map {; $_ => 1 } qw(
263	h1 h2 h3 h4 h5 h6
264	p div pre plaintext address blockquote
265	xmp listing
266	center
267
268	multicol
269	iframe ilayer nolayer
270	bgsound
271
272	hr
273	ol ul dir menu li
274	dl dt dd
275	ins del
276
277	fieldset legend
278
279	map area
280	applet param object
281	isindex script noscript
282	table
283	center
284	form
285	),
286	keys %isFormElement,
287	keys %isPhraseMarkup, # And everything phrasal
288	keys %isTableElement,
289	;
290
291
292	=item hashset %HTML::Tagset::isHeadOrBodyElement
293
294	This hashset includes all elements that I notice can fall either in
295	the head or in the body.
296
297	=cut
298
299	%isHeadOrBodyElement = map {; $_ => 1 }
300	qw(script isindex style object map area param noscript bgsound);
301	# i.e., if we find 'script' in the 'body' or the 'head', don't freak out.
302
303
304	=item hashset %HTML::Tagset::isKnown
305
306	This hashset lists all known HTML elements.
307
308	=cut
309
310	%isKnown = (%isHeadElement, %isBodyElement,
311	map{; $_=>1 }
312	qw( head body html
313	frame frameset noframes
314	~comment ~pi ~directive ~literal
315	));
316	# that should be all known tags ever ever
317
318
319	=item hashset %HTML::Tagset::canTighten
320
321	This hashset lists elements that might have ignorable whitespace as
322	children or siblings.
323
324	=cut
325
326	%canTighten = %isKnown;
327	delete @canTighten{
328	keys(%isPhraseMarkup), 'input', 'select',
329	'xmp', 'listing', 'plaintext', 'pre',
330	};
331	# xmp, listing, plaintext, and pre are untightenable, and
332	# in a really special way.
333	@canTighten{'hr','br'} = (1,1);
334	# exceptional 'phrasal' things that ARE subject to tightening.
335
336	# The one case where I can think of my tightening rules failing is:
337	# <p>foo bar<center> <em>baz quux</em> ...
338	# ^-- that would get deleted.
339	# But that's pretty gruesome code anyhow. You gets what you pays for.
340
341	#==========================================================================
342
343	=item array @HTML::Tagset::p_closure_barriers
344
345	This array has a meaning that I have only seen a need for in
346	C<HTML::TreeBuilder>, but I include it here on the off chance that someone
347	might find it of use:
348
349	When we see a "E<lt>pE<gt>" token, we go lookup up the lineage for a p
350	element we might have to minimize. At first sight, we might say that
351	if there's a p anywhere in the lineage of this new p, it should be
352	closed. But that's wrong. Consider this document:
353
354	<html>
355	<head>
356	<title>foo</title>
357	</head>
358	<body>
359	<p>foo
360	<table>
361	<tr>
362	<td>
363	foo
364	<p>bar
365	</td>
366	</tr>
367	</table>
368	</p>
369	</body>
370	</html>
371
372	The second p is quite legally inside a much higher p.
373
374	My formalization of the reason why this is legal, but this:
375
376	<p>foo<p>bar</p></p>
377
378	isn't, is that something about the table constitutes a "barrier" to
379	the application of the rule about what p must minimize.
380
381	So C<@HTML::Tagset::p_closure_barriers> is the list of all such
382	barrier-tags.
383
384	=cut
385
386	@p_closure_barriers = qw(
387	li blockquote
388	ul ol menu dir
389	dl dt dd
390	td th tr table caption
391	);
392
393	# In an ideal world (i.e., XHTML) we wouldn't have to bother with any of this
394	# monkey business of barriers to minimization!
395
396	###########################################################################
397
398	=item hashset %isCDATA_Parent
399
400	This hashset includes all elements whose content is CDATA.
401
402	=cut
403
404	%isCDATA_Parent = map {; $_ => 1 }
405	qw(script style xmp listing plaintext);
406
407	# TODO: there's nothing else that takes CDATA children, right?
408
409	# As the HTML3 DTD (Raggett 1995-04-24) noted:
410	# The XMP, LISTING and PLAINTEXT tags are incompatible with SGML
411	# and derive from very early versions of HTML. They require non-
412	# standard parsers and will cause problems for processing
413	# documents with standard SGML tools.
414
415
416
417	###########################################################################
418
419	=back
420
421	=head1 CAVEATS
422
423	You may find it useful to alter the behavior of modules (like
424	C<HTML::Element> or C<HTML::TreeBuilder>) that use C<HTML::Tagset>'s
425	data tables by altering the data tables themselves. You are welcome
426	to try, but be careful; and be aware that different modules may or may
427	react differently to the data tables being changed.
428
429	Note that it may be inappropriate to use these tables for I<producing>
430	HTML -- for example, C<%isHeadOrBodyElement> lists the tagnames
431	for all elements that can appear either in the head or in the body,
432	such as "script". That doesn't mean that I am saying your code that
433	produces HTML should feel free to put script elements in either place!
434	If you are producing programs that spit out HTML, you should be
435	I<intimately> familiar with the DTDs for HTML or XHTML (available at
436	C<http://www.w3.org/>), and you should slavishly obey them, not
437	the data tables in this document.
438
439	=head1 SEE ALSO
440
441	L<HTML::Element>, L<HTML::TreeBuilder>, L<HTML::LinkExtor>
442
443	=head1 COPYRIGHT
444
445	Copyright 1995-2000 Gisle Aas; copyright 2000 Sean M. Burke.
446
447	This library is free software; you can redistribute it and/or
448	modify it under the same terms as Perl itself.
449
450	=head1 AUTHOR
451
452	Current maintainer: Sean M. Burke, E<lt>sburke@cpan.orgE<gt>
453
454	Most of the code/data in this module was adapted from code written by
455	Gisle Aas E<lt>gisle@aas.noE<gt> for C<HTML::Element>,
456	C<HTML::TreeBuilder>, and C<HTML::LinkExtor>.
457
458	=cut
459
460	1;