X M L

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X M L

• Extensible Markup Language

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XML examples from -
www.w3schools.com
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• like HTML, but not a replacement
• XML describes data. HTML displays data.
• easier to expand and upgrade systems 
• tags are user-defined
• cross-platform
• software and hardware independent

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• XML separates data from HTML
• XML data is stored outside HTML
• or stored inside HTML (Data Islands)
• will be main language for
• financial information exchange

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• stores data in plain text files
• software- and hardware-independent data sharing.
• easier to expand and upgrade systems 
• stores data in databases and other files.
• used to create new languages
• WAP (Wireless Markup Language)
• WML (Wireless Application Protocol).
• markup Internet applications for handheld devices
• Hopefully all future applications will do data
  exchange in XML.

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• XML Syntax
• simple and strict
• all elements must have closing tag
• tags are case sensitive

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• lt?xml version"1.0" encoding"ISO-8859-1"?gt
  XML declaration not part of XML document no
  closing tag
• ltnotegt
• root element doc is a note
• lttogtTovelt/togt
• next 4 lines child elements to, from,
  heading, body
• ltfromgtJanilt/fromgt
• ltheadinggtReminderlt/headinggt
• ltbodygtDon't forget me this weekend!lt/bodygt
• lt/notegt
• end of root element

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XML Syntax

• elements must be correctly nested
• documents must have a root element
• attribute values always in quotes
• date12/11/2002
• spacing is preserved
• new line is always stored as LF (line feed)
• comment syntax similar HTML comments

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XML Elements

• Documents can be extended to carry more
  information.
• elements related - parents and children
• Element is everything from element's start tag to
  end tag (including tags).
• 4 types of element content
• Element content
• Mixed content
• Simple content
• Empty content
• elements can have attributes

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• ltbookgt root element -
• has element content because it has other
  elements in it (children)
• lttitlegtMy First XMLlt/titlegt children, siblings or
  sisters (title, prod, chapter) have
  same parent
• ltprod id"33-657" media"paper"gtlt/prodgt prod
  empty content
• has attributes, but no information (attribute
  named media has value paper)
• ltchaptergtIntroduction to XML
• chapter - mixed content - has text and other
  elements
• ltparagtWhat is HTMLlt/paragt
• para - simple content (or text content)
  contains only text
• ltparagtWhat is XMLlt/paragt
• lt/chaptergt
• ltchaptergtXML Syntax
• ltparagtElements must have a closing taglt/paragt
• ltparagtElements must be properly nestedlt/paragt

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• Element Naming Rules
• can contain
• letters, number, other characters
• cannot start with
• number, punctuation character, or letters xml,
  XML, Xml
• cannot contain
• spaces, hyphen (-), period (.), colon ()

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The End