Transforming XML Part I

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Transforming XML Part I

• Document Navigation with XPath

John Arnett, MSc Standards Modeller Information
and Statistics Division NHSScotland Tel [phone]
8073 (x2073) mailtoJohn.Arnett_at_isd.csa.scot.nhs.u
k http//isdscotland.org/xml
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Contents

• Document Processing
• Nodes and Trees
• XPath Locating Nodes
• Summary
• Find Out More

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Document Processing

• The XSL Family
• XPath (XML Path Language)
• XSLT (Extensible Stylesheet Language
  Transformations)
• XSL aka XSL-FO (Extensible Stylesheet Language
  Formatting Objects)

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Document Processing

• XPath
• Used to locate specific parts of an XML source
  document efficiently and effectively
• XPath v1.0 W3C Recommendation

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Document Processing

• XSLT
• Used to transform XML documents to another XML or
  non-XML form esp. HTML
• XSLT v1.0 W3C Recommendation
• v2.0 W3C Working Draft
• Uses XPath for locating document content

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Document Processing

• XSL(-FO)
• Used to format XML documents into fixed sized
  folios for publication
• XSL v1.0 W3C Recommendation
• Uses XSLT for document transformation

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Document Processing

• Transformation and formatting
• XPath used to locate nodes for input
• XSLT used to transform input and generate result
  tree
• XSL-FO used to format output document

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Document Processing
Source Tree
Stylesheet Processor
Formatted Output
Result Tree
Format
Transform
Style sheet
Adapted from XSLT Basics slide presentation by
Paul Spencer, alphaXML
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Trees and Nodes

• XML document is viewed as a source tree
  containing different node types

• root
• element
• text
• attribute

• namespace
• processing instruction
• comment

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Trees and Nodes

• XML Appointment example

lt!-- radiology appointment --gt ltAppointment
deptCodeRADIOgt ltPatient upiABC-123-456gtJoh
n Smith ltPhoneNogt0141 662 2673lt/PhoneNogt
lt/Patientgt ltCliniciangtAlison
Younglt/Cliniciangt ltSlot attendDate2003-08-05gt
ltStartTimegt143000lt/StartTimegt lt/Slotgt
lt/Appointmentgt
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Trees and Nodes

• XPath view of Appointment source tree

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XPath Locating Nodes

• XPath expressions (location paths)
• Used to navigate source tree and locate nodes for
  input
• Comprised of one or more location steps
• axis node test (optional) predicate
• May contain functions, e.g.
• position(), count(node-set), last()

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XPath Locating Nodes

• Axes
• Specify node locations relative to the current
  (context) node self
• May traverse tree forwards or backwards

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XPath Locating Nodes

• Axes for forward traversal
• child
• attribute
• descendant-or-self
• descendant
• following
• following-sibling
• namespace

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XPath Locating Nodes

• Axes for reverse traversal
• parent
• ancestor
• ancestor-or-self
• preceding
• preceding-sibling

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XPath Locating Nodes

• Node Tests
• Refine node set selection
• select all nodes of same type
• node() select all nodes of any type
• Select all nodes of type text(), comment() or
  processing-instruction()
• Select all nodes with specified name

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XPath Locating Nodes

• Select Clinician element node
• childAppointment/childClinician or
• Appointment/Clinician

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XPath Locating Nodes

• Select upi attribute node
• childPatient/attributeupi or
• Patient/_at_upi

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XPath Locating Nodes

• Select all descendant text nodes
• /descendant-or-selfnode()/childtext() or
• //text()

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XPath Locating Nodes

• Select parent of StartTime element
• parentnode() or ..

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XPath Locating Nodes

• Using wildcards
• child or

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XPath Locating Nodes

• Abbreviating location steps
• child and text() can usually be omitted

childAppointment/childClinician/childtext()
Appointment/Clinician

• attribute _at_
• Patient/_at_upi
• self()node .
• parentnode() ..

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XPath Locating Nodes

• Abbreviating Location Paths
• /descendant-or-selfnode()/ //
• /descendant-or-selfnode()/childtext()
  //text()

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In Summary

• XML document processing
• XPath - node location
• XSLT - transformation
• XSL-(FO) - document formatting
• XPath used to navigate source tree
• Transformation performed by applying style sheet
  to source document

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Find Out More

• The Extensible Stylesheet Language Family (XSL)
• www.w3.org/Style/XSL/
• W3C XML Path Language v1.0 Specification
• www.w3.org/TR/xpath
• TopXML XSLT XPath Tutorial
• www.vbxml.com/xsl/tutorials/intro/default.asp