Common Subset - Revision history

GPHemsley: Redirected page to HTML vs. XHTML

2013-07-09T14:26:23Z

← Older revision		Revision as of 14:26, 9 July 2013
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	The common subset intersecting HTML5 and XHTML5 is a subset of both syntaxes meant to create . The common subset is only implicitly defined by the HTML and XHTML specification because they have many syntax elements in common. A document is said to use the common subset when it can parse correctly with both the XML parser and the HTML parser.		#REDIRECT [[HTML vs. XHTML]]

	A document using the '''conforming''' common subset is conforming with the specification whether it is interpreted as HTML or XHTML. The conforming common subset rejects any element with are not conforming in either of the two DOM variants.

	A document using the common subset can be served as HTML (text/html media type) or XHTML (with an XML media type). The media type is what the browser use to decide if it'll be parsed as HTML or XHTML and which varient of the DOM is used.


	~~== Common Syntax ==~~

	~~[TBD]~~

	~~== Limitations from HTML ==~~

	* The [http://blog.whatwg.org/faq/#~~doctype doctype is required] to be <code><!DOCTYPE html></code>~~
	* Tag and attribute names must be lowercase.
	* XMLish end tag tailing slash must not be used with non-void elements; they'll be ignored by the HTML parser and are invalid in HTML.
	* XMLish CDATA blocks will not work.
	* HTML does not allow mixing with other XML dialects.
	* <code>script</code> elements cannot contain the text <code></script</code> followed by <code>/</code>, <code>></code> or whitespace unless in an escaped text span (<code><!--...--></code>).

	~~== Limitations from XML and XHTML ==~~

	* The doctype, optional in XHTML but mandatory in HTML, must match case-sensitivly this <code><!DOCTYPE html></code> to be well-formed and valid in XHTML.
	* Well-formness contrains, not respecting these will generate fatal errors in XHTML.
	** Comments cannot contain double-hyphens (<code>--</code>).
	** Start tags and end tags must be balenced correctly, unless they're void element.
	** Void tags must always be closed by a tailing slash (<code>/></code>).
	** All attributes values must be quoted. Attributes without value are disallowed.
	** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).
	** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [~~http://www.w3.org/TR/REC-xml/#charsets XML charsets]~~
	** Others constrains defined in the [~~http://www.w3.org/TR/REC-xml/ XML specification].~~
	* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form. External scripts and stylesheets are unaffected.
	** There is a trick to allow <code><</code> and <code>&</code> which involves using CDATA blocks and inside JavaScript comments. See the workarounds section.
	* <code>noscript</code> has no effect in XHTML.
	* <code>document.write()</code> does not work in XHTML.
	* Entity references cannot be used in XHTML (excluding the 5 predefined entities: <code>&amp;</code>, <code>&lt;</code>, <code>&gt;</code>, <code>&quot;</code> and <code>&apos;</code>).
	* The namespace declaration (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear in HTML ~~on the condition that is has the value "http://www~~.~~w3.org/1999/xhtml". <code><html xmlns="http://www.w3.org/1999/xhtml"></code>~~
	* DOM Core APIs are case-sensitive in XHTML, scripts should always use lowercase to be compatible.
	* Style rules are matching case sensitivly in XHTML~~, stylesheets should always use lowercase tag and attribute names to be compatible.~~

	~~== Markup Issues and Workarounds ==~~

	~~=== Character Set ===~~

	~~HTML~~

	~~<meta http-equiv="Content-Type" value="text/html;charset=utf-8">~~

	~~XHTML / XML~~

	~~<?xml version="1.0" encoding="utf-8"?>~~

	~~Workaround: HTTP Content-Type header with encoding specified:~~

	~~Content-Type: text/html;charset=utf-8~~
	~~Content-Type: application/xhtml+xml;charset=utf-8~~


	~~=== Scripts & Style ===~~

	~~HTML~~

	~~<script type="text/javascript">~~
	~~if (a < 0 && a > 10) alert("A not in range (0 < a < 10).")~~
	~~</script>~~

	~~XML / XHTML~~

	~~<script type="text/javascript">~~
	~~if (a &lt; 0 &amp;&amp; a > 10) alert("A not in range (0 &lt; a &lt; 10).")~~
	~~</script>~~

	or

	~~<script type="text/javascript">~~
	~~<![CDATA[~~
	~~if (a < 0 && a > 10) alert("A not in range (0 < a < 10).")~~
	]]>
	~~</script>~~

	~~Workaround: Commented CDATA block around the problemantic part of the script, or the whole script:~~

	~~<script type="text/javascript">~~
	~~/* <![CDATA[ */~~
	~~if (a < 0 && a > 10) alert("A not in range (0 < a < 10).")~~
	~~/* ]]> */~~
	~~</script>~~

	This works because HTML puts the CDATA block markers textually inside the script, but as they're then inside comments it has no effect, and the CDATA block allows the XML parser to work with unescaped character data. The same trick can be applied to the <code>style</code> element when it contains <code><</code> or <code>&</code>. This CDATA dance is only needed where <code>script</code> or <code>style</code> contains <code>&</code> or <code><</code>.

	Note that the element must not contain the string <code>]]></code>, or the XML wouldn't be well-formed. It cannot contain <code></script</code> followed by <code>/</code>, <code>></code> or whitespace, or it would close the element in HTML. Both can be worked around with backslash escaping.

Zcorpan: /* Scripts & Style */

2008-12-28T08:38:32Z

Scripts & Style

← Older revision		Revision as of 08:38, 28 December 2008
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	</script>		</script>

	This works because HTML puts the CDATA block markers textually inside the script, but as they're then inside comments it has no effect, and the CDATA block allows the XML parser to work with unescaped character data. The same trick can be applied to the <code>style</code> element when it contains <code><</code> or <code>&</code>.		This works because HTML puts the CDATA block markers textually inside the script, but as they're then inside comments it has no effect, and the CDATA block allows the XML parser to work with unescaped character data. The same trick can be applied to the <code>style</code> element when it contains <code><</code> or <code>&</code>. This CDATA dance is only needed where <code>script</code> or <code>style</code> contains <code>&</code> or <code><</code>.

	Note that the element must not contain the string <code>]]></code>, or the XML wouldn't be well-formed~~, and it may not~~ contain <code></</code>~~, or it would be non-conformant HTML. In all cases, this is only needed where~~ <code>~~script~~</code> or <code>~~style</code~~> ~~contains <code>&~~</code> or ~~<code><</code>~~.		Note that the element must not contain the string <code>]]></code>, or the XML wouldn't be well-formed. It cannot contain <code></script</code> followed by <code>/</code>, <code>></code> or whitespace, or it would close the element in HTML. Both can be worked around with backslash escaping.

Zcorpan: lang/xml:lang is now moot since both are allowed

2008-12-28T08:34:00Z

lang/xml:lang is now moot since both are allowed

← Older revision		Revision as of 08:34, 28 December 2008
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	Content-Type: text/html;charset=utf-8		Content-Type: text/html;charset=utf-8
	Content-Type: application/xhtml+xml;charset=utf-8		Content-Type: application/xhtml+xml;charset=utf-8


	~~=== Language ===~~

	~~HTML~~

	~~<html lang="en">~~

	~~XML / XHTML~~

	~~<html xml:lang="en">~~

	~~Workaround: HTTP Content-Language header:~~

	~~Content-Language: en~~

	~~[http://www.whatwg.org/specs/web-apps/current-work/#lang HTML 5 Spec]~~
	~~[http://www.w3.org/TR/html4/struct/dirlang.html#h-8.1.2 HTML 4 Spec]~~

	Note that there is no conforming workaround to switch language for different parts of a document. There is a method which will work however: if you use HTML's lang attribute, instead of the conformant xml:lang, browser will correctly deduce the language of the element. But this will make the document non-conforming when served with an XML media type and interpreted as XHTML.

Zcorpan: is allowed in XHTML5, and content-location probably doesn't work as a workaround anyway

2008-12-28T08:31:48Z

<base> is allowed in XHTML5, and content-location probably doesn't work as a workaround anyway

← Older revision		Revision as of 08:31, 28 December 2008
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	== Markup Issues and Workarounds ==		== Markup Issues and Workarounds ==

	~~=== Base URI ===~~

	~~HTML:~~

	~~<base src="uri">~~

	~~XML / XHTML:~~

	~~<html xml:base="uri">~~

	~~Workaround: HTTP Content-Location header:~~

	~~Content-Location: uri~~

	~~[http://www.w3.org/TR/html4/struct/links.html#h-12.4.1 HTML 4 Spec]~~


	=== Character Set ===		=== Character Set ===

Zcorpan: /* Limitations from XML and XHTML */

2008-12-28T08:26:30Z

Limitations from XML and XHTML

← Older revision		Revision as of 08:26, 28 December 2008
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	** Void tags must always be closed by a tailing slash (<code>/></code>).		** Void tags must always be closed by a tailing slash (<code>/></code>).
	** All attributes values must be quoted. Attributes without value are disallowed.		** All attributes values must be quoted. Attributes without value are disallowed.
	** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> ~~inside attribute values or~~ anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).		** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).
	** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]		** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]
	** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].		** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].
Line 35:		Line 35:
	* <code>document.write()</code> does not work in XHTML.		* <code>document.write()</code> does not work in XHTML.
	* Entity references cannot be used in XHTML (excluding the 5 predefined entities: <code>&amp;</code>, <code>&lt;</code>, <code>&gt;</code>, <code>&quot;</code> and <code>&apos;</code>).		* Entity references cannot be used in XHTML (excluding the 5 predefined entities: <code>&amp;</code>, <code>&lt;</code>, <code>&gt;</code>, <code>&quot;</code> and <code>&apos;</code>).
	* The namespace declaration (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear ~~on the html element~~ in HTML on the condition that is has the value "http://www.w3.org/1999/xhtml". <html xmlns="http://www.w3.org/1999/xhtml">		* The namespace declaration (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear in HTML on the condition that is has the value "http://www.w3.org/1999/xhtml". <code><html xmlns="http://www.w3.org/1999/xhtml"></code>
	* DOM ~~apis~~ are case-sensitive in XHTML, scripts should always use lowercase to be compatible.		* DOM Core APIs are case-sensitive in XHTML, scripts should always use lowercase to be compatible.
	* Style rules are matching case sensitivly in XHTML, stylesheets should always use lowercase tag, attribute ~~and class~~ names to be compatible.		* Style rules are matching case sensitivly in XHTML, stylesheets should always use lowercase tag and attribute names to be compatible.

	== Markup Issues and Workarounds ==		== Markup Issues and Workarounds ==

Zcorpan: /* Limitations from HTML */

2008-12-28T08:22:21Z

Limitations from HTML

← Older revision		Revision as of 08:22, 28 December 2008
Line 17:		Line 17:
	* XMLish CDATA blocks will not work.		* XMLish CDATA blocks will not work.
	* HTML does not allow mixing with other XML dialects.		* HTML does not allow mixing with other XML dialects.
	* ~~HTML does not support~~ <code>p</code> elements ~~may~~ contain ~~structured inline level elements including~~ <code>~~blockquote~~</~~code>, <code>dl~~</code>, <code>~~menu<~~/~~code>, <code>ol~~</code>, <code>~~ul</code>, <code~~>~~pre~~</code> ~~and~~ <code>~~table</code>~~.		* <code>script</code> elements cannot contain the text <code></script</code> followed by <code>/</code>, <code>></code> or whitespace unless in an escaped text span (<code><!--...--></code>).
	* <code>~~script</code> elements cannot contain <code></~~</code>.

	== Limitations from XML and XHTML ==		== Limitations from XML and XHTML ==

Michel Fortin: Some corrections.

2006-12-09T13:43:02Z

Some corrections.

← Older revision		Revision as of 13:43, 9 December 2006
Line 28:		Line 28:
	** Void tags must always be closed by a tailing slash (<code>/></code>).		** Void tags must always be closed by a tailing slash (<code>/></code>).
	** All attributes values must be quoted. Attributes without value are disallowed.		** All attributes values must be quoted. Attributes without value are disallowed.
	** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> inside ~~comments~~ or anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).		** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> inside attribute values or anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).
	** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]		** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]
	** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].		** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].
	* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form. External scripts and stylesheets are unaffected.		* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form. External scripts and stylesheets are unaffected.
	** There is a ~~tricky way~~ to ~~make that work~~ which involves using CDATA blocks and inside JavaScript comments.		** There is a trick to allow <code><</code> and <code>&</code> which involves using CDATA blocks and inside JavaScript comments. See the workarounds section.
	* <code>noscript</code> has no effect in XHTML.		* <code>noscript</code> has no effect in XHTML.
	* <code>document.write()</code> does not work in XHTML.		* <code>document.write()</code> does not work in XHTML.
Line 107:		Line 107:
	<script type="text/javascript">		<script type="text/javascript">
	if (a &lt; 0 &amp;&amp; a > 10) alert("A not in range (0 &lt; a &lt; 10).")		if (a &lt; 0 &amp;&amp; a > 10) alert("A not in range (0 &lt; a &lt; 10).")
			</script>

			or

			<script type="text/javascript">
			<![CDATA[
			if (a < 0 && a > 10) alert("A not in range (0 < a < 10).")
			]]>
	</script>		</script>

Michel Fortin at 13:08, 9 December 2006

2006-12-09T13:08:44Z

@@ Line 18: / Line 18: @@
 * HTML does not allow mixing with other XML dialects.
 * HTML does not support <code>p</code> elements may contain structured inline level elements including <code>blockquote</code>, <code>dl</code>, <code>menu</code>, <code>ol</code>, <code>ul</code>, <code>pre</code> and <code>table</code>.
 == Limitations from XML and XHTML ==
@@ Line 30: / Line 31: @@
 ** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]
 ** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].
-* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form, unless they're in a CDATA block which would make the document non-conforming on the HTML side (althoug it should still be possible to make it work). External scripts and stylesheets are unaffected.
+* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form. External scripts and stylesheets are unaffected.
 * <code>noscript</code> has no effect in XHTML.
 * <code>document.write()</code> does not work in XHTML.
@@ Line 91: / Line 93: @@
 Note that there is no conforming workaround to switch language for different parts of a document. There is a method which will work however: if you use HTML's lang attribute, instead of the conformant xml:lang, browser will correctly deduce the language of the element. But this will make the document non-conforming when served with an XML media type and interpreted as XHTML.

Michel Fortin: /* Limitations from XML and XHTML */ Added reference to XML character spec and fixed some entities.

2006-12-08T20:44:53Z

Limitations from XML and XHTML: Added reference to XML character spec and fixed some entities.

Michel Fortin: /* Limitations from HTML */

2006-12-08T20:38:36Z

Limitations from HTML

← Older revision		Revision as of 20:38, 8 December 2006
Line 12:		Line 12:
	== Limitations from HTML ==		== Limitations from HTML ==

	[~~TBD~~]		* The [http://blog.whatwg.org/faq/#doctype doctype is required] to be <code><!DOCTYPE html></code>
			* Tag and attribute names must be lowercase.
			* XMLish end tag tailing slash must not be used with non-void elements; they'll be ignored by the HTML parser and are invalid in HTML.
			* XMLish CDATA blocks will not work.
			* HTML does not allow mixing with other XML dialects.
			* HTML does not support <code>p</code> elements may contain structured inline level elements including <code>blockquote</code>, <code>dl</code>, <code>menu</code>, <code>ol</code>, <code>ul</code>, <code>pre</code> and <code>table</code>.

	== Limitations from XML and XHTML ==		== Limitations from XML and XHTML ==

← Older revision		Revision as of 20:44, 8 December 2006
Line 23:		Line 23:
	* The doctype, optional in XHTML but mandatory in HTML, must match case-sensitivly this <code><!DOCTYPE html></code> to be well-formed and valid in XHTML.		* The doctype, optional in XHTML but mandatory in HTML, must match case-sensitivly this <code><!DOCTYPE html></code> to be well-formed and valid in XHTML.
	* Well-formness contrains, not respecting these will generate fatal errors in XHTML.		* Well-formness contrains, not respecting these will generate fatal errors in XHTML.
	** Comments cannot contain double-hyphens (--).		** Comments cannot contain double-hyphens (<code>--</code>).
	** Start tags and end tags must be balenced correctly, unless they're void element.		** Start tags and end tags must be balenced correctly, unless they're void element.
	** Void tags must always be closed by a tailing slash ("/>").		** Void tags must always be closed by a tailing slash (<code>/></code>).
	** All attributes values must be quoted. Attributes without value are disallowed.		** All attributes values must be quoted. Attributes without value are disallowed.
	** All < and & in the text must be escaped, so is > inside comments or anywhere in the text when preceded by ]] (where it would be ~~CData~~ section end marker).		** All <code><</code> and <code>&</code> in the text must be escaped, so is <code>></code> inside comments or anywhere in the text when preceded by <code>]]</code> (where it would be CDATA section end marker).
	** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF)		** Some characters are illegal in XML (U+0009, U+000A, U+000D, U+0020-U+D7FF, U+E000-U+FFFD, U+10000-U+10FFFF) [http://www.w3.org/TR/REC-xml/#charsets XML charsets]
	** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].		** Others constrains defined in the [http://www.w3.org/TR/REC-xml/ XML specification].
	* <code>script</code> and <code>style</code> elements may not contain < or & in their unescaped form, unless they're in a CDATA block which would make the document non-conforming on the HTML side (althoug it should still be possible to make it work). External scripts and stylesheets are unaffected.		* <code>script</code> and <code>style</code> elements may not contain <code><</code> or <code>&</code> in their unescaped form, unless they're in a CDATA block which would make the document non-conforming on the HTML side (althoug it should still be possible to make it work). External scripts and stylesheets are unaffected.
	* <code>noscript</code> has no effect in XHTML.		* <code>noscript</code> has no effect in XHTML.
	* <code>document.write()</code> does not work in XHTML.		* <code>document.write()</code> does not work in XHTML.
	* Entity references cannot be used in XHTML (excluding the 5 predefined entities: &, <, >, " and ').		* Entity references cannot be used in XHTML (excluding the 5 predefined entities: <code>&amp;</code>, <code>&lt;</code>, <code>&gt;</code>, <code>&quot;</code> and <code>&apos;</code>).
	* The namespace declaration (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear on the html element in HTML on the condition that is has the value "http://www.w3.org/1999/xhtml". <html xmlns="http://www.w3.org/1999/xhtml">		* The namespace declaration (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear on the html element in HTML on the condition that is has the value "http://www.w3.org/1999/xhtml". <html xmlns="http://www.w3.org/1999/xhtml">
	* DOM apis are case-sensitive in XHTML, scripts should always use lowercase to be compatible.		* DOM apis are case-sensitive in XHTML, scripts should always use lowercase to be compatible.