The Future of the Web: XML and XHTML

1
The Future of the Web XML and XHTML

• Lee Honeycutt
• English 313

2
Outline

• History of Tagging
• Description and Uses of XML
• Description of XHTML
• XHTML Conversion Tips

3
History of Tagging

• Generalized Markup Language (GML) - developed in
  1969 at IBM based on earlier concepts of generic
  document markup languages that humans could
  understand. Still used on 90 of IBMs documents.
• Standardized Generalized Markup Language (SGML) -
  International standard adopted in mid-1980s and
  used by large corporations to standardize
  document production, retrieval, and printing.

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History of Tagging (cont.)

• HTML - begun in 1990 by CERNs Tim Berners-Lee,
  who was looking for a simple subset of SGML that
  could be used for online documents.
• HTMLs limitations became evident as technology
  progressed, and SGML was way too complex for
  enhancing HTML.
• Extensible Markup Language (XML)- developed by
  the W3C based on a simple subset of SGML.

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What is XML?

• XML is a metalanguage, i.e. a language that
  defines the rules and symbols of another
  language.
• XML is not used on the web, but instead used to
  define other markup languages, such as XHTML, the
  replacement of HTML.
• Allows us to define markup languages customized
  to our individual needs instead of relying on
  HTML tags.

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Impact of XML

• Greater flexibility and complexity.
• Users define their own tagging system through the
  use of a Document Type Definition (DTD).
• DTD, supplemented by Extensible Stylesheet
  Language (XSL), tells the browser how to parse
  various XML tags.
• HTML has its own standardized DTD that defines
  how tags should be read in browsers, though
  browsers dont always conform.

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Anatomy of a DTD

• A DTD is a collection of XML entity and element
  declarations and comments.
• Entity - name/value pairs that make the DTD easy
  to parse. EXlt!ENTITY fruit kumquat or other
  citrusgt
• Elements - defines actual markup tags.
  EXlt!ELEMENT name (first, middle?,
  last)gtlt!ELEMENT street (PCDATA)gtlt!ELEMENT city
  (PCDATA)gt

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XML Example

• ltaddress typehomegt
• ltnamegt
• ltfirstgtLeelt/firstgt
• ltlastgtHoneycuttlt/lastgt
• lt/namegt
• ltstreetgt3938 Christytown Roadlt/streetgt
• ltcitygtStory Citylt/citygt
• ltstategtIowalt/stategtltzip length9gt50248-1234lt/z
  ipgt
• lt/addressgt

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Uses of XML

• Creating dynamic web pages served out of
  databases.
• Ability to share and repurpose documents across a
  variety of media. InDesign 3.0 and Acrobat 6.0
  have full XML capabilities.
• Synchronized Multimedia Integration Language
  (SMIL).
• Standardizing HTML.

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What is XHTML?

• A markup language that uses a specific XML DTD
  for creation of web pages.
• Designed to make HTML more harmonious with rules
  of larger markup languages and to support display
  on various types of media.
• Three XHTML DTDs
• Strict excludes deprecated tags and elements.
• Transitional closest to HTML (includes
  deprecated)
• Frameset Transitional, designed for frames.

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XHTML Opener

• lt?xml version1.0 encodingUTF-8?gt
• lt!DOCTYPE html
• PUBLIC -//W3C//DTD XHTML 1.0 Transitional//En
  http//www.w3.org/TR/xhtml1/DTD/xhtml1-transitiona
  l.dtd gt
• lthtml xmlnshttp//www.w3.org/1999/xhtml
  xmllangen langengt
• ltheadgt
• lttitlegtWelcome to XML Worldlt/titlegt
• Etc, etc.

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XHTML Restrictions

• All elements must be nested correctly.Wrong
  ltbgtDo it ltigtrightlt/bgtlt/igt.Correct ltbgtDo it
  ltigtrightlt/igtlt/bgt.
• All tags that can contain content or other tags
  must have an end tag.
• Those without content must put space-slash
  within tag. ltimg srcphoto.jpg /gt
• All tag and attribute names are
  case-sensitive.ltH1gt is not the same as lth1gt

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XHTML Restrictions (cont.)

• Attribute values must be quotedlttable rows3gt,
  not lttable rows3gt
• All attributes must have a value.lthr
  noshadenoshadegt, not lthr noshadegt
• Put JavaScript and StyleSheets in external files
  to avoid special character problems.
• Use the id attribute instead of name for
  anchor links (name is deprecated).

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Why Use XHTML?

• Non-compliant pages may look fine now, but they
  will create problems down the road.
• Conversion is getting easier all the time.
  Current versions of GoLive and Dreamweaver are
  XHTML compatible.
• Most corporate style sheets are demanding XHTML
  compliance for repurposing. Also used in content
  management systems.