Overview of XML

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Overview of XML

• Terry Butler
• Director, Research Computing
• Arts Resource Centre
• 2005 February

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Overview of XML

• What is XML?
• History of text encoding technologies
• XML in Corpus Linguistics
• Tools for XML

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What is XML?

• What is XML?
• Extensible Markup Language (XML) is a simple,
  very flexible text format (from the W3C page)
• it is a W3C standard
• w3c.org/TR/2004/REC-xml-20040204/
• it is a human-readable language for text markup
• and an easy-to-process language for information
  exchange between computer systems

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XML vs. HTML

• HTML has a predefined set of tags which are meant
  to display information via a particular program
  (a web browser)
• XML is a language to define any set of tags which
  describe text the text can be shared, displayed
  and transformed in many ways

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XML Basics

• a DTD (document type definition) defines a class
  of documents each document is an instance
• the document is created under control of the DTD,
  so it can be made well-formed and valid
• not well formed
• ltgreetingsgtIm pleased to ltactiongtbe
  herelt/greetingsgtlt/actiongt.
• not valid
• ltgreetingsgtIm pleased to ltactiongtbe
  herelt/actiongt.lt/grootingsgt
• there are shortcuts for composing
• entities nbsp myAddress
• the underlying character set is UNICODE

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History of Text Encoding Technologies

• from GML to SGML to XML
• www.oasis-open.org/cover/sgmlhist0.html
• presentation-oriented markup (like Word) vs.
  descriptive markup
• My Summer Holiday
• ltheadgtMy Summer Holidaylt/headgt

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History of Text Encoding Technologies

• SGML (ISO 8879) was powerful but complex
• used in publishing, technical documentation
  fields
• difficult for humans to craft, computers to
  process
• HTML appeared, and the web took off
• simple SGML-like syntax, few tags
• browsers could format the text for viewing
• no rules checking!
• SGML proved very hard to adapt to the web
• browsers are the final arbiter

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History of Text Encoding Technologies

• XML designed to overcome these obstacles
• document can be processed without the DTD
• minimization and simplification of syntax
• XML has many affiliated technologies
• style sheets
• linking
• queries (searching)

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Tools for XML

• XML Spy Altova
• powerful XML editing and stylesheet capabilities
• excellent visualization and validation features
• XMetaL Blast Radius
• simple XML editor
• familiar user interface (like word processor)
• Turbo XML TIBCO
• integrates with content repositories
• has a transformation creation tool (XML
  Transform)

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XML in Corpus Linguistics

• XML in Corpus Linguistics
• SGML, now XML used, to markup text with features
  of interest
• users can both search and display the text with
  or without the tags
• examples
• BNC
• ANC

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BNC word class shown
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BNC word class and tags shown
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TAPoR Project

• computer infrastructure (workshop, servers,
  storage)
• funded by Canada Foundation for Innovation
• resources to convert, store, query, transform and
  display textual data (encoded or not)
• more information and projects at
  tapor.ualberta.ca