What is XML

1
What is XML?

• eXtensible Markup Language
• A subset of SGML (Standard Generalized Markup
  Language)
• Mechanism to identify structures in a document
• Markup language for documents containing
  structured information
• Self-Descriptive
• Buzz Word

2
XML and HTML

• Similar in nature
• lttagsgt
• Labels
• Elements
• lttagsgt plus content
• Reference Specification
• WWW consortium (W3C)
• HTML transitional
• XHTML
• XML 1.0

3
XML Document Structure

• Declaration
• Elements
• Attributes
• Character Data
• Processing Instructions
• Comments
• Entity References

4
Declaration

• ltxml version1.0 encodingiso-8859-1gt
• Start of the file
• Optional
• Future proof

5
Elements

• ltReportgt
• XML Report
• lt/Reportgt
• Highest level termed as the root element
• Contains
• Start tag
• Some Content
• End tag

6
Attributes

• ltReport AuthorSteviegt
• XML Report
• lt/Reportgt
• Contains
• Name
• Value

7
Character Data

• ltReport AuthorSteviegt
• lttypegtXML lt/typegt Report
• lt/Reportgt
• Element Content
• Special Symbols
• and lt
• See Entity References

8
Comments

• lt!-- This is a Comment --gt

9
Entity References
10
Processing Instructions

• lt?, and end with the string ?gt
• Show a processing instruction at the appropriate
  place in the node tree (DOM)
• Firing a processing instruction event (SAX)

11
Well-Formed XML

• Tags must be nested properly
• All start tags must have end tags
• Use quotation marks properly for tag attributes
• Use entity references

12
Document Type Definition

• Set of rules
• May be included in the document itself
• May be linked externally
• Confirming to a DTD
• Well-formed
• valid

13
Document Type Definition

• lt!DOCTYPE rootElementName
• insert declarations here
• gt
• lt!Element element (sub1, sub2,,subn)gt
• lt!ATTLIST element name (value1value2)

14
XML Parsing

• Document Object Model (DOM)
• Simple API for XML (SAX)

15
Document Object Model (DOM)

• Document Model driven
• Build a tree model of the elements in the
  document
• Allow for application to access the tree
• DOM XML parser
• Converts XML documents into Java Tree object model

16
Simple API for XML (SAX)

• Event driven
• SAX XML parser processes elements serially
• XML application provides callback functions to
  handle elements

17
Freely Available XML Parsers

• Apache Software Foundation Xerces XML Parser
  (xml.apache.org)
• Open source
• Oracle XML Parser Version 2 (www.oracle.com/xml)
• Must register
• SAX2 Parser (www.megginsion.com/SAX)
• Freely available

18
References

• http//www.w3.org/XML
• http//www.xml.com
• http//www.w3schools.com/xml/default.asp