Dr' Maria Indrawan maria'indrawaninfotech'monash'edu'au

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Dr. Maria Indrawanmaria.indrawan_at_infotech.monash.
edu.au

• XML An Introduction

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XML Document an Example

• ltbookshopgt
• ltbookgt
• lttitlegt Harry Potter and the Sorcerers
  Stonelt/titlegt
• ltauthorgt
• ltinitialsgtJ.Klt/initialsgt
• ltsurnamegt Rowlinglt/surnamegt
• lt/authorgt
• ltprice value16.95gtlt/pricegt
• lt/bookgt
• lt/bookshopgt

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What is XML

• XMLExtensible Markup Language.
• XML is a way to represent data gt data structure
• Utilise the mark ups to define
• structure
• semantics gt to a certain level.
• Markup Languages
• HTML
• SGML
• WWW Consortium(W3C) recommendation.
• www.w3c.org

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HTML vs XML
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Why do we need XML?

• Distributed applications need to share data.
• XML allow data to be shared across distributed
  application because
• The underlying data format is plain text.
• The structure and the meaning of the data can be
  tightly defined.
• The need to support different format of
  presentation. (eg. mobile phone, PDA, web,
  printed materials).
• Unlike HTML, XMLs markups concerned with the
  structure and the meaning of the data itself.
• Presentation is dealt by querying and
  manipulating the XML document through the use of
  manipulation language such as XSL.
• Separation of data and presentation.

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Some XML Related Technologies

• DTD and XSD
• Data definition.
• XSL (XSLT and XSL-FO)
• Presentation.
• XPath
• Navigating the XML document.
• Xlink, Xpointer
• Linking elements within XML document or between
  XML documents.
• DOM and SAX
• APIs to manipulate XML document.

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XML in Web Browser

• To display an xml document in a web browser, the
  web browser needs to have an XML Parser.
• Example msxml

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XML Parser

• A parser is required to read and manipulate XML
  documents.
• What is a parser?
• Parse in linguistic means to divide language into
  smaller parts that can be analyzed webopedia.
• What does an XML parser do?
• Read the XML documents as a plain text and
  transform it into a data structure, typically
  tree, in the memory.
• The applications, such as web browser, access the
  data structure and process the data according to
  their objectives.

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Current Usage of XML (1)

• XML as a data transport or communication platform
• Interoperability
• Web Services
• WSDL, SOAP, UDDI
• Workflow
• BPEL4WS
• Semantic support
• Semantic Web
• RDF
• Both interoperability and semantic support
• Semantic Web services
• OWL(Web Ontology Language)
• Agent Technology
• DAML(DARPA Agent Markup Language ).

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Current Usage of XML (2)

• XML as a database
• Native XML database
• Tamino
• XML-Relational Hybrid
• Oracle
• DB2
• Issues for using XML as a native database
• Lack of formal theory in describing the model.
• The concept of relations
• Data Integrity
• Transaction

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XML Issues

• Processing
• Text vs binary processing
• Security

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Elements
Root Element (compulsory)
Branch Elements
attribute
Leaf Element
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Element

• The basic building block of XML markups.
• It may contains
• Text
• Other elements (child elements)
• Attributes
• Character Data
• Other markup, eg comments
• Delimited with a start-tag and an end-tag.
• Element can be empty.
• The end-tag CANNOT be omitted as in HTML.
• Each tag must consist a valid element type name.

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Elements Name

• Elements Name (Tags name) is CASE SENSITIVE.
• ltBOOKgt ?ltBookgt?ltbookgt
• Trailing space is legal but will be ignored
• ltBOOK gt ltBOOKgt

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Empty Element

• Has no content.
• May be associated with attribute.
• Example
• ltimg srclogo.pnggtlt/imggt
• can be abbreviated into
• ltimg srclogo.png/gt

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Attributes

• Information regarding the element.
• If elements are nouns of XML then attributes
  are its adjective.
• lttagname attribute_nameattribute_valuegt

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Attributes vs Element

• Determine by the semantic contents.
• Attributes are characteristics of an element.

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Character References

• Use to display characters that are not supported
  by the input device (keyboard).
• entering using US-ASCII keyboard.
• Format NNNNN or xXXXX
• N decimal
• X hexadecimal
• Example gt 36 OR x24

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Entity References

• Entities may be defined and used for
• Representing character used in mark-up
• lt lt
• amp
• String
• IR Information Retrieval
• Predefined entities lt, gt, quot, etc

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Character Data

• To escape blocks of text containing characters
  which would otherwise be recognized as markup.
• lt!CDATAgt
• lt!CDATAltgreetinggtHello, world!lt/greetinggtgt

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Character Data(2)

• ltexamplegt
• lt!CDATAWarn-Disclaimerltcopy 2001
  PMgtgt
• lt/examplegt
• ltexamplegt
• ampWarn-ampDisclaimerampltampcopy
  2001 ampPM ampgtgt
• lt/examplegt

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Processing Instruction(PI)

• Processing instructions (PIs) allow documents to
  contain instructions for applications.
• lt?target instruction ?gt
• Target is used to identify the application or
  other object to which the PI is directed.
• lt?xml-stylesheet hrefmystyle.css
  typetext/cssgt

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XML Document Basic Components

• Elements.
• Attributes.
• Character and Entity References.
• Character Data (CDATA).
• Processing Instruction.
• Comments.

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Comments

• Syntax
• lt!- comment text --gt
• Comments cannot be used within element tags.
• lttaggt some content lttag lt! it is illegal --gtgt
• Comments may never be nested.
• lt! Comments cannot lt! be nested --gt like this
  --gt

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Structure of XML Document

• XML document has to be well-formed.
• Conform to syntax requirements
• Conform to a simple container structure
• Common structure of XML document
• Prologue
• Body
• Epilogue

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Prologue

• Includes
• XML Declaration
• lt?xml version1.0 encodingutf-8
  standaloneyesgt
• Version is mandatory, encoding and standalone are
  optional
• Document Type Declaration
• lt!DOCTYPE
• It is not DTDDocument Type Definition
• A simple well-formed XML does not need it.
• Schema declaration

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Body Epilogue

• Body
• Contains 1 or more elements
• The contents
• Epilogue
• Hardly used
• Can be used to identify end of document

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Well-formed XML Document

• Contains one root element.
• All the tags have a valid tags name.
• There is no overlapping tags.