XML eXtensible Markup Language

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XML eXtensible Markup Language

• by Darrell Payne

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Experience

• Logicon / Sterling Federal
• C, C, JavaScript/Jscript, Shell Script, Perl
• XML Training
• XML Training Course
• 2001 DevXCon Training Conference
• Currently developing XML course for Logicon
• Darrell.Payne_at_Sterling-fsg.com

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XML eXtensible Markup Language

• Standard General Markup Language(SGML)
• Meta-tag language
• Used for creating other markup languages
• Standard adopted for SGML in 1986
• Hyper Text Markup Language(HTLM)
• Application of SGML
• Formatting Language
• eXtensible Markup Language(XML)
• Meta-tag language
• XML DATA
• World Wide Web Consortium W3C
• ((!Standard) (Specification)) // c code
  humor
• XML Version 1.0 February 1998
• XML is not designed to replace HTML

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SGML HTML XML diagram
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XML Family of Tools and Their Relationship
Linking and Pointing
Style and Transformation
Underlying And Object Model
Complex Data Modeling
Programmatic Interface
XML Developer's Guide - McGraw Hill - Page 12
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HTML vs. XML

• Html
• Predefined tags
• Syntax is loose
• File extensions usually .html of .htm
• Not required to be Well Formed
• Some closing tags optional
• Attribute value quotes may be omitted
• XML
• User defined tags
• Syntax is exact
• File extensions usually .xml
• Closing tags mandatory
• Required to be Well - Formed

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Well - Formed

• All XML documents must be Syntactically correct!
• Single root element
• All element start tags have end tags
• XML is case sensitive
• Properly nested tags
• ltfirstgtltsecondgtlt/firstgtlt/secondgt //error
• ltfirstgtltsecondgtlt/secondgtlt/firstgt //correct
• Attributes values in quotes
• value or value

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Basic XML Parts

• Markup
• Tags
• Attributes, names and values
• Character Data
• Text
• PCDATA
• CDATA
• Binary
• XML document has two main sections
• Prolog
• Root
• Misc
• Optional and considered superfluous

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Simple XML File

• lt?xml version"1.0"?gt
• lt!-- My first XML file --gt
• ltdocumentgt
• ltmessagegtHello World!lt/message gt
• lt/document gt
• lt!--
• More Comments
• --gt

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Declaration

• If used
• lt?xml version"1.0"?gt required
• Declaration optional
• Specifies version to which document conforms
• XML documents without XML declaration might be
  assumed to conform to the latest version
• Other declaration examples
• lt?xml version"1.0" encoding"UTF-8"?gt optional
• Default Good for ASCII text 8 bit characters
• UTF-16 Good for foreign 16 bit characters
• Used for Unicode characters
• To stay uniform use with 8 or 16
• lt?xml version"1.0" standalone"yes"?gt optional
• No external subset referenced default
• lt?xml version"1.0" encodingUTF-8
  standalone"yes?gt

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Comments

• lt!-- My first XML file --gt
• lt!--
• More Comments
• --gt
• XML uses same comment syntax as HTML

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Root Element

• ltdocumentgt
• lt/documentgt
• Lines preceding root element are contained in the
  Prolog
• All XML documents must contain only one root
  element
• All other elements are child elements

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Child Element

• ltdocumentgt
• ltmessagegtHello World!lt/message gt
• lt/document gt

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Sibling Element

• ltdocumentgt
• ltmessagegtHello World!lt/message gt
• ltmessagegtGoodbye World!lt/message gt
• ltmessage2gtNothing more to add!lt/message2 gt
• lt/document gt

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Updating Microsofts Internet Explorer

• instmsia.exe
• Updates Microsofts Installer
• msxml3sp1.exe
• Updates Microsofts Internet Explorer
• IE now has built-in XML parser msxml

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Create XML Document

• Include declaration
• lt?xml version"1.0"?gt
• Create root element ltcis_classgt
• Create child element ltcis_345gt
• Enter child element text student name
• Save file with .xml extension
• Open using Internet Explorer
• After success, add siblings elements and retest
  using Internet Explorer

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Document viewed in Microsoft's Internet Explorer
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More about Elements

• Element types
• Container Element
• Contains other elements
• Data Element
• Contains DATA
• Mixed Content
• Contains other elements and DATA
• Empty Element
• Contains no elements or DATA

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Container Element

• Contains other elements
• ltouter_elementgt
• ltinner_elementgt
• ltyet_another_elementgt
• ltcan_we_go_any_deepergt
• Some text way down here in the center of it all
• lt/can_we_go_any_deepergt
• lt/yet_another_elementgt
• lt/inner_elementgt
• lt/outer_elementgt

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Data Element

• Contains DATA
• Parsable Character Data
• PCDATA
• Character Data
• CDATA

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PCDATA

• Contains text
• Can be parsed by parser
• Can contain all text except
• lt
• gt

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Entity References

• XML provides built in entity references
• lt
• gt
• quot
• apos
• amp

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CDATA

• Contains text
• Is a declaration
• Can contain reserved characters
• lt, gt, , ,
• Starts with / ends with
• lt!CDATA
• Data would be here
• gt
• CDATA can not contain
• gt

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Declarations

• lt!-- --gt
• lt!DOCTYPE gt
• lt!CDATA gt
• lt!ELEMENT gt
• lt!IGNORE gt
• lt!INCLUDE gt
• lt!NOTATION gt
• lt!ENTITY gt
• lt!ATTLIST gt

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Why CDATA section

• C code example
• CDATA example
• If (this-gtgetX() lt 5 array10 ! 3)
• cerr ltlt this-gtdisplayError()
• PCDATA example
• If (this-gtgetX() lt 5 ampamp array10
  ! 3)
• cerr ltlt this-gtdisplayError()

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Mixed Content

• Elements and PCDATA combined
• ltouter_elementgt
• outer element stuff
• ltinner_elementgt
• inner element stuff
• lt/inner_elementgt
• more outer element stuff
• lt/outer_elementgt

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Empty Element

• Contains no text or data
• May have an attribute
• ltempty_elementgtlt/empty_elementgt
• ltempty_element/gt
• Short cut notation for empty element
• Does this look unfamiliar
• HTML example of such a type of tag
• ltimg src image.gifgt //Non Well Formed
• ltimg src image.gif /gt //Well Formed

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Elements
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Create XML Document 2

• Include declaration
• Create root element ltcis_class2gt
• Create child element ltcis_345gt
• Enter child element text student name
• Create child element ltcis_346gt
• Child to root, sibling to ltcis_345gt
• Make this an empty element
• Create child element ltcis_347gt
• Child to root, sibling to ltcis_345gt
• Enter C code example in PCDATA section
• Create child element ltcis_348gt
• Enter same C code in a CDATA section
• Save file
• Open using Internet Explorer

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XML Parser DOM SAX

• Required to process an XML document
• C, Java, Python, Perl
• Parsers are of type
• Document Object Model(DOM)
• Tree structure
• Like a drive directory structure
• Slower and requires large amounts of memory
• Simple API for XML(SAX)
• Events driven
• Events tags, text, etc.
• Smaller, faster, but requires programmer to deal
  with data
• Validating and non-validating

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XML Structure

• Logical structure
• Document divided into units
• Allows sub units
• XML is a logical tree structure document
• Physical structure
• Data stored inside document
• Data stored outside document
• Entities one example

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Valid

• Conforms to some schema
• schema s
• Document Type Definition(DTD)
• Schema
• By definition, all valid XML documents are Well
  Formed documents

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DTD Document Type Definition

• Document Type Declaration(DTD)
• File extension of .dtd
• DTD is not an XML document
• DTD is a schema s
• Introduced into an XML document via the Document
  Type Declaration
• lt!DOCTYPE gt
• Three types of DOCTYPE declarations
• Internal Subset
• Contained in the Prolog
• External Subset
• Exist in different file
• Prolog contains reference to file containing DTD
• Referenced using key work
• SYSTEM or PUBLIC
• Internal Subset and External Subset combination

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Internal Subset

• lt?xml version"1.0"?gt
• lt!-- My second XML file --gt
• lt!DOCTYPE document
• lt!ELEMENT document (message)gt
• lt!ELEMENT message (PCDATA)gt
• gt
• ltdocumentgt
• ltmessagegtHello World!lt/messagegt
• lt/documentgt
• lt!--
• More Comments
• --gt

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External Subset

• lt?xml version"1.0"?gt
• lt!-- My second XML file --gt
• lt!DOCTYPE document SYSTEM "HelloWorld.dtd"gt
• ltdocumentgt
• ltmessagegtHello World!lt/messagegt
• lt/documentgt
• lt!--
• More Comments
• --gt

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DTD for HelloWorld.xml

• lt!ELEMENT document (message)gt
• lt!ELEMENT message (PCDATA)gt

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Internal Subset and External Subset combination I

• lt?xml version"1.0"?gt
• lt!-- My second XML file --gt
• lt!DOCTYPE document SYSTEM "HelloWorld3.dtd"
• lt!ELEMENT document (message)gt
• gt
• ltdocumentgt
• ltmessage gt
• ltmessage2gt
• lt/message2gt
• lt/messagegt
• lt/documentgt
• lt!--
• More Comments
• --gt

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Internal Subset and External Subset combination II

• lt!-- External declarations --gt
• lt!ELEMENT message (message2)gt
• lt!ELEMENT message2 (PCDATA)gt

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Putting it all together

• HelloWorld3.dtd
• lt!-- External declarations --gt
• lt!ELEMENT message (message2)gt
• lt!ELEMENT message2 (PCDATA)gt
• HelloWorld3.xml
• lt?xml version"1.0"?gt
• lt!-- My second XML file --gt
• lt!DOCTYPE document SYSTEM "HelloWorld3.dtd"
• lt!ELEMENT document (message)gt
• gt
• ltdocumentgt
• ltmessage gt
• ltmessage2gt
• lt/message2gt
• lt/messagegt
• lt/documentgt
• lt!--
• More Comments
• --gt

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XML Validator
Type in HelloWorld3.xml
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Create XML Document 3

• Create root element ltsession1gt
• Create child element of session1ltsession2gt
• Enter child element text xml class
• Create child element of session2ltsession3gt
• Enter child element text class information
• Create child element of session3ltsession4gt
• Enter child element text more
• Create DTD for this file dtd_info.dtd
• Reference file in XML document
• Save files
• Open validate_vbs.html
• Enter .xml file name
• Validate

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Schema

• Schemas are XML documents
• Schemas can be manipulated via a parser
• More complicated than DTDs
• Schemas have ElementTypes

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Schema vs. DTD

• lt!-- External declarations --gt
• lt!ELEMENT document (message, message2, message3)gt
• lt!ELEMENT message (message4, message5 )gt
• lt!ELEMENT message2 (PCDATA)gt
• lt!ELEMENT message3 (PCDATA)gt
• lt!ELEMENT message4 (PCDATA)gt
• lt!ELEMENT message5 (PCDATA)gt

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Schema vs. DTD II

• lt?xml version"1.0" encoding"UTF-8"?gt
• lt!--W3C Schema generated by XML Spy v3.5
  (http//www.xmlspy.com)--gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2000/10/X
  MLSchema" elementFormDefault"qualified"gt
• ltxsdelement name"document"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement ref"message"/gt
• ltxsdelement ref"message2"/gt
• ltxsdelement ref"message3"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

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Schema vs. DTD III

• ltxsdelement name"message"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement ref"message4"/gt
• ltxsdelement ref"message5"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• ltxsdelement name"message2" type"xsdstring"/gt
• ltxsdelement name"message3" type"xsdstring"/gt
• ltxsdelement name"message4" type"xsdstring"/gt
• ltxsdelement name"message5" type"xsdstring"/gt
• lt/xsdschemagt

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Topics not covered

• Namespace Whitespace
• Xpath Xpointer
• Xlink
• XSL XSLT
• SOAP DDI
• Web Services
• SMIL
• XHTML