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INF201 Fall2010 Intro. to Info. Technologies. Department of Informatics University at Albany – SUNY Original Source: w3schools.com Prepared by Xiao Liang, fall 2010 Adapted from Choi , Spring2009. What is XML. XML stands for EXtensible Markup Language
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INF201 Fall2010Intro. to Info. Technologies Department of Informatics University at Albany – SUNY Original Source: w3schools.com Prepared by Xiao Liang, fall 2010 Adapted from Choi, Spring2009
WhatisXML • XML stands for EXtensible Markup Language • XML is a markup language much like HTML • XML was designed to carry data, not to display data • XML tags are not predefined. You must define your own tags • XML is designed to be self‐descriptive • XML is a W3C Recommendation
XML vs. HTML • XML was designed to transport and store data. • You design your own tags • HTML was designed to display data. • Tags are predefined. • XML does not DO anything. XML was created to structure, store, and transport information.
WhyXML? • XML iscomputerunderstandable,andcomputerusable • XML provideastandardway,avoidingerrors • XML provides a robust and durable format for information storage and transmission. Robust because it is based on a proven standard, and can thus be tested and verified; durable (persistent) because it uses plain-text file formats which will outlast proprietary binary ones. • XML provides a common syntax for messaging systems for the exchange of information between applications • XML is free. Not just free of charge (free as in beer) but free of legal encumbrances (free as in speech). • XML information can be manipulated programmatically (under machine control), so XML documents can be pieced together from disparate sources, or taken apart and re-used in different ways. They can be converted into any other format with no loss of information. • XML lets you separate form (appearance) from content. Forreference:http://xml.silmaril.ie/basics/whyxml/
How Can XML be Used? • XML Separates Data from HTML • XML Simplifies Data Sharing and Data Transport • XML data is stored in plain text format. This provides a software‐and hardware‐independent way of storing data. • Platform independent • A lot of new Internet languages are created with XML
XMLexample <?xml version="1.0"?> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
XMLSyntax • XML declaration<?xml version="1.0"?> • Root element (Required)<note> • Child element(<to>,<from>,<heading>,<body>) • All XML Elements Must Have a Closing Tag • XML Tags are Case Sensitive<Letter> is different from the tag <letter> • XML Elements Must be Properly Nested<to><title>This is incorrect</to></title>notright • XML Attribute Values Must be Quoted <note date="09/29/2009">
XMLdocumentstructure <root> <child> <subchild>.....</subchild> </child></root>
XML NamingRules • XML Naming Rules • Names can contain letters, numbers, and other characters • Names cannot start with a number or punctuation character • Names cannot start with the letters xml (or XML, or Xml, etc) • Names cannot contain spaces
XML Attributes • Attributes often provide information that is not a part of the data.<file type="gif">computer.gif</file> • It is NOT recommended to use attributesattributes cannot contain multiple values (elements can) • attributes cannot contain tree structures (elements can) • attributes are not easily expandable (for future changes)
XML Validation • XML with correct syntax is "Well Formed" XML. • XML validated against a DTDis "Valid" XML. • XML SchemaXML‐based alternative to DTD • W3schools.com XML Validator
XML Style • DisplayingXML with CSS HTML is designed for content being sent to a browser. XML can be converted to HTML and read by browsers • Displaying XML with XSLT eXtensibleStylesheet Language Transformations To transform XML to HTML
Howtocreatexmlfile? • Eitherusenotepadordreamweaver • DonotforgetputXML declaration<?xml version="1.0"?> • Saveasfilename.xml