XHTML
Jump to navigation
Jump to search
Definition
- XHTML is a family of current and future Web document types and modules that reproduce, subset, and extend HTML4.01. XHTML family document types are XML conformant, and designed to work in conjunction with XML-based editors and user agents.
XHTML documents
Valid XHTML documents
- XHTML documents must be wellformed and valid according to the XML specification, except that an XML declaration is not mandatory (only encouraged).
In addition:
- It must conform to the constraints expressed in one of the three variants (defined by DTDs)
- The root element of the document must be html
- The root element of the document must contain an xmlns declaration for the XHTML namespace. Examples:
<html xmlns= "http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <h:html xmlns:h="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
- There must be a DOCTYPE declaration in the document prior to the root element.
- The DTD subset must not be used to override any parameter entities in the DTD.
- An XML declaration on top of the file is mandatory if the character set used is different from UTF-8 or UTF-16.
XHTML Versions
- XHTML 1.X (26 jan 2000, revised 1 Aug 2002)
- XHTML 1.0 transitional
- XHTML 1.0 strict
- XHTML 1.0 frameset
- XHTML 2.x
Example
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Virtual Library</title>
</head>
<body>
Moved to <a href="http://example.org/">example.org</a>.
</body> </html>
Composite documents
- XHTML can include other namespaced languages, e.g. SVG or MathML or your own XML. However, for the moment it is not possible to validate composite documents.
- MathML example
<?xml version="1.0" encoding="iso-8859-1"?> <xhtml:html xmlns:xhtml="http://www.w3.org/1999/xhtml"> <xhtml:body> <xhtml:h1>A Compound Document</xhtml:h1> <xhtml:p>A simple formula using MathML in XHTML.</xhtml:p> <mathml:math xmlns:mathml="http://www.w3.org/1998/Math/MathML"> <mathml:mrow> <mathml:msqrt> <mathml:mn>49</mathml:mn> </mathml:msqrt> <mathml:mo>=</mathml:mo> <mathml:mn>7</mathml:mn> </mathml:mrow> </mathml:math> </xhtml:body> </xhtml:html>
- It is also possible to include XHTML tags in any XML document markup. E.g. here is an example:
<?xml version="1.0" ?> <?xml-stylesheet href="xml_plus_xhtml.css" type="text/css"?> <page xmlns:html="http://www.w3.org/1999/xhtml" updated="jan 2007"> <title>Hello friend</title> <list> <html:img src="photo.jpg"/> <item price="10"> White plate </item> <item price="20"> Gold plate </item> <item price="15"> Silver plate </item> </list> <comment> Written by <html:a href="http://tecfa.unige.ch/tecfa-people/schneider.html">DKS/Tecfa</html:a> , feb 2007 </comment> </page>
Current issues
- XHTML is badly supported by IE6 and IE7. I.e. current (14:49, 12 March 2007 (MET)) Microsoft browser do not recognize the application/xhtml+xml mimetype, which makes it difficult to include XSLT stylesheets or other languages such as SVG or MathML.
There are workarounds to somewhat deal with IE 6/7:
- Using server-side rewrite rules
- Serve a document as either HTML or XML and use *.htm *.html or *.xml file extensions from a standard web server. If you send XHTML as simple HTML files you will loose all XML-related advantages.
Links
Standards
- HTML, Latest Version (XHTML 1.0 as of 14:49, 12 March 2007 (MET)]
- XHTML 1.0