XHTML

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XHTML
Source http//www.ccse.kfupm.edu.sa/mibuhari/swe
444/SWE444.htm
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What is XHTML?

• XHTML stands for EXtensible HyperText Markup
  Language
• XHTML is the next generation of HTML
• XHTML is aimed to replace HTML
• XHTML is almost identical to HTML 4.01
• XHTML is a stricter and cleaner version of HTML
• XHTML is a reformulation of HTML into a language
  that conforms to the XML 1.0 Recommendation
• XHTML Family document types are all XML-based,
  and ultimately are designed to work in
  conjunction with XML-based user agents

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Why XHTML?

• XHTML is a combination of HTML and XML
• XML is a markup language where everything has to
  be marked up correctly, which results in
  "well-formed" documents
• XHTML consists of all the elements in HTML 4.01
  combined with the syntax of XML
• We have reached a point where many pages on the
  WWW contain "bad" HTML
• XHTML pages can be read by all XML enabled devices

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How is XHTML better than HTML?

• Extensibility
• it is a metalanguage, which enables one to write
  a Document Type Definition (DTD) and define the
  rules of the language so the document can be
  interpreted by the document receiver .
• Portability
• much of Internet access could be carried out on
  non-PC platforms such as palm computers,
  televisions, automobiles, telephones, etc.
• In most cases these devices will not have the
  computing power of a desktop computer, and will
  not be designed to accommodate ill-formed HTML as
  do current browsers (bloated with code to handle
  sloppy or proprietary HTML).

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Differences Between XHTML and HTML

• The Most Important Differences
• XHTML elements must be properly nested
• XHTML documents must be well-formed
• Tag names must be in lowercase
• All XHTML elements must be closed

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Elements Must Be Properly Nested

• In HTML some elements can be improperly nested
  within each other like this
• ltbgtltigtThis text is bold and italiclt/bgtlt/igt
• In XHTML all elements must be properly nested
  within each other like this
• ltbgtltigtThis text is bold and italiclt/igtlt/bgt
• A common mistake in nested lists, is to forget
  that the inside list must be within an li element

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Documents Must Be Well-formed

• All XHTML elements must be nested within the
  lthtmlgt root element
• All other elements can have sub (children)
  elements. Sub elements must be in pairs and
  correctly nested within their parent element.
• The basic document structure is

lthtmlgt ltheadgt ... lt/headgt ltbodygt ...
lt/bodygt lt/htmlgt
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Tag Names Must Be in Lower Case

• This is because XHTML documents are XML
  applications
• XML is case-sensitive
• Tags like ltbrgt and ltBRgt are interpreted as
  different tags

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All XHTML Elements Must Be Closed

• Non-empty elements must have an end tag
• Empty Elements Must also Be Closed
• Empty elements must either have an end tag or the
  start tag must end with /gt

This is a breakltbr /gt Here comes a horizontal
rulelthr /gt Here's an image ltimg src"happy.gif"
alt"Happy face" /gt
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XHTML Syntax

• Writing XHTML demands a clean HTML syntax
• Some more XHTML Syntax Rules
• Attribute names must be in lower case
• Attribute values must be quoted
• Attribute minimization is forbidden
• The id attribute replaces the name attribute
• The XHTML DTD defines mandatory elements

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Attribute Minimization is Forbidden
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The id Attribute replaces the Name Attribute

• HTML 4.01 defines a name attribute for the
  elements a, applet, frame, iframe, img, and map
• In XHTML the name attribute is deprecated. Use id
  instead.
• ltimg src"picture.gif" id"picture1" /gt
• To make your XHTML compatible with today's
  browsers, you should add an extra space before
  the "/" symbol

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Mandatory XHTML Elements

• All XHTML documents must have a DOCTYPE
  declaration
• This is a minimum XHTML document template

lt?xml version"1.0" encoding"UTF-8"?gt lt!DOCTYPE
html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN" "http//www.w3.org/TR/xhtml1/DTD
/xhtml1-transitional.dtd"gt lthtml
xmlns"http//www.w3.org/1999/xhtml"
xmllang"en" lang"en"gt ltheadgt lttitlegt...
lt/titlegt lt/headgt ltbodygt ... lt/bodygt lt/htmlgt
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XHTML Document Type Definitions (DTD)

• The lt!DOCTYPEgt is Mandatory
• The 3 Document Type Definitions
• DTD specifies the syntax of a web page in SGML
• An XHTML DTD describes in precise the allowed
  syntax and grammar of XHTML markup.
• There are currently 3 XHTML 1.0 document types
• STRICT
• TRANSITIONAL
• FRAMESET

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The 3 Document Type Definitions

• XHTML 1.0 Strict
• Use this when you want really clean markup, free
  of presentational clutter. Use this together with
  Cascading Style Sheets.
• XHTML 1.0 Transitional
• Use this when you need to take advantage of
  HTML's presentational features and when you want
  to support browsers that don't understand
  Cascading Style Sheets.
• XHTML 1.0 Frameset
• Use this when you want to use HTML Frames to
  partition the browser window into two or more
  frames.

lt!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN" "http//www.w3.org/TR/xhtml1/DTD
/xhtml1-transitional.dtd"gt
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XHTML Validation

• An XHTML document is validated against a Document
  Type Definition (DTD)
• Test your XHTML with the W3C Validator
• http//validator.w3.org/
• XHTML Tag List
• http//www.w3schools.com/xhtml/xhtml_reference.asp
  
• XHTML Attributes
• http//www.w3schools.com/xhtml/xhtml_standardattri
  butes.asp

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W3C Recommendations

• XHTML 1.0 (Recommendation since January 2000)
• Three "flavors" of XHTML 1.0
• XHTML 1.0 Strict
• XHTML 1.0 Transitional
• XHTML 1.0 Frameset The complete
• XHTML Basic (Recommendation since December 2000)
• XHTML Basic is the second Recommendation in a
  series of XHTML specifications.
• The XHTML Basic document type includes the
  minimal set of modules required to be an XHTML
  Host Language document type.
• It includes images, forms, basic tables, and
  object support.
• It is designed for Web clients that do not
  support the full set of XHTML features such as
  mobile phones, PDAs, pagers, and settop boxes.

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W3C Recommendations

• Modularization of XHTML (Recommendation since
  April 2001)
• Modularization of XHTML is the third
  Recommendation in a series of XHTML
  specifications.
• This Recommendation specifies an abstract
  modularization of XHTML and an implementation of
  the abstraction using XML Document Type
  Definitions (DTDs).
• This modularization provides a means for
  subsetting and extending XHTML, a feature needed
  for extending XHTML's reach onto emerging
  platforms.
• Modularization of XHTML will make it easier to
  combine with markup tags for things like vector
  graphics, multimedia, math, electronic commerce
  and more.

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W3C Recommendations

• XHTML 1.1 - Module-based XHTML (Recommendation
  since May 2001)
• While XHTML 1.1 looks very similar to XHTML 1.0
  Strict, it is designed to serve as the basis for
  future extended XHTML Family document types, and
  its modular design makes it easier to add other
  modules as needed or integrate itself into other
  markup languages.
• XHTML 2.0 (first working draft August 2002)
• XHTML 2.0 is a markup language intended for rich,
  portable web-based applications. While the
  ancestry of XHTML 2.0 comes from HTML 4, XHTML
  1.0, and XHTML 1.1, it is not intended to be
  backward compatible with its earlier versions.