transforming xml part i document navigation with xpath john arnett, msc standards modeller...

Transforming XML Part I

Document Navigation with XPath

John Arnett, MScStandards ModellerInformation and Statistics DivisionNHSScotlandTel: 0131 551 8073 (x2073)mailto:[email protected]://isdscotland.org/xml

Contents

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

Document Processing

• The XSL Family– XPath (XML Path Language)– XSLT (Extensible Stylesheet

Language Transformations)– XSL aka XSL-FO (Extensible

Stylesheet Language Formatting Objects)

Document Processing

• XPath– Used to locate specific parts of

an XML source document efficiently and effectively

– XPath v1.0 W3C Recommendation

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

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

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

Document Processing

Adapted from XSLT Basics slide presentation by Paul Spencer, alphaXML

Source Tree

Source Tree

Style sheet

Style sheet

FormatTransformResult Tree

Result Tree

Formatted Output

Formatted Output

Stylesheet Processor

Trees and Nodes

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

– root– element– text– attribute

– namespace– processing

instruction– comment

Trees and Nodes

• XML Appointment example

 <Appointment deptCode=”RADIO”>

<Patient upi=”ABC-123-456”>John Smith<PhoneNo>0141 662 2673</PhoneNo>

</Patient><Clinician>Alison Young</Clinician><Slot attendDate=”2003-08-05”>

<StartTime>14:30:00</StartTime></Slot>

</Appointment>

Trees and Nodes

commentra d io lo g y ap p o in tm e nt

attributed e p tC o de

R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

text0 1 41 66 2 26 73

elementP h o ne N o

elementP a tie n t

textA liso n Y o u ng

elementC lin ic ia n

attributea tten d D a te2 0 0 3 -0 8 -05

text1 4 :3 0 :00

elementS ta rtT im e

elementS lo t

elementA p po in tm e nt

root

• XPath view of Appointment source tree

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()


• Axes– Specify node locations relative

to the current (context) node = self

– May traverse tree forwards or backwards


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


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


• 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


commentra d io lo g y ap p o in tm e n t


R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

elementP h o ne N o

elementP a tie n t





elementS lo t


root

• Select Clinician element nodechild::Appointment/child::Clinician orAppointment/Clinician


• Select upi attribute nodechild::Patient/attribute::upi orPatient/@upi



R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

elementP h o ne N o

elementP a tie n t





elementS lo t


root


commentra d io lo g y ap p o in tm e nt


R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

text0 1 41 66 2 26 73

elementP h o ne N o

elementP a tie n t




text1 4 :3 0 :00


elementS lo t


root

• Select all descendant text nodes/descendant-or-self::node()/child::text() or//text()




R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

elementP h o ne N o

elementP a tie n t





elementS lo t


root

• Select parent of StartTime elementparent::node() or ..


• Using wildcardschild::* or *



R A D IO

attributeu p i

A B C -12 3 -4 56

textJo h n S m ith

elementP h o ne N o

elementP a tie n t





elementS lo t


root


• Abbreviating location steps–child:: and text() can usually

be omittedchild::Appointment/child::Clinician/child::text() = Appointment/Clinician

–attribute:: = @Patient/@upi

–self()::node = . –parent::node() = ..


• Abbreviating Location Paths/descendant-or-self::node()/ = ///descendant-or-self::node()/child::text()

= //text()

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

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

http://www.w3.org/Style/XSL/

http://www.w3.org/Style/XSL/

http://www.w3.org/TR/xpath

http://www.w3.org/TR/xpath

http://www.vbxml.com/xsl/tutorials/intro/default.asp



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