The XSL Transformation

1
The XSL Transformation
2
Introduction
3
Why Styling?

• XML
• Concentrate on structure
• Not concentrate on appearance
• To View XML documents, we need to format or style
  them
• The styling is directly related to and derived
  from the structure of the document
• Two W3C styling sheets
• CSS Cascading Styling Sheet
• XSL XML Style-sheet Language

4
Cascading Style Sheet (CSS)

• Originally for HTML
• A set of rules that tell the browser which font,
  style, and margin to use to display the text

• section.title
• font-family Garamond, Time News Roman,
  seriffont-size 10pt
• margin5px
• displayblock
• font-style italic

5
XML Stylesheet Language (XSL)

• Support transforming the document before display
• A transformation lang.
• A formatting lang.

• ltPgtltBgt Table of Content lt/Bgtlt/Pgt
• ltULgt
• ltxslfor-each select article/section/titlegtltLI
  gtltAgt
• ltxslvalue-of select./gt lt/Agtlt/LIgt
• lt/xslfor-eachgt
• lt/ULgt

6
XSL

• XSL is organized into two parts
• XSLT XSL Transformation
• Move data from one XML rep. to another
• Electronic commerce, Electronic data exchange,
  Metadata change
• Standardize Nov. 16, 1999
• XSLFO XSL Formatting Objects
• XSLFO and CSS are very similar in scope
• In practice
• XSLT is useful
• CSS is preferred to XSLFO

7
XSL Processors

• Microsoft
• LotusXSL
• www.alphaworks.ibm.com
• James Clark
• www.jclark.com

8
Concepts of XSLT (I)
Source Document
Resulting Document
XSLProcessor
XSLT Style Sheet
9
Concept of XSLT (II)

• XSLT A language to specify transformation of XML
  documents
• Add elements specifically for viewing
• Add the logo or address of the company
• Create new content from an existing one
• Create table of content
• Create views for different users
• Concert between different DTDs
• Transform XML documents into HTML

10
Concept of XSLT (III)

• XSLT transforms one XML tree into another
• select particular nodes from the input tree
• reorder/process nodes
• output nodes

• Tree nodes
• The root
• Elements
• Text
• Attributes
• Namespaces
• Processing instructions
• Comments

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(No Transcript)
12
Basic XSLT
13
Example Scenario

• A monthly e-zine, Pineapplesoft Link
• E-mail to subscribers
• Post a copy on Web
• Use one document structure
• XML
• Two different presentations
• XSLT

14
Using LotusXSL

• e-zine Example xml_example/chap05
• e-zine.xml
• e-zine.xsl
• Set up the LotusXSL Environment
• set pathc\jdk1.1.8\binPATH
• set classpathXSL\lotusxsl.jarCLASSPATH
• set classpathXSL\xalan.jarXSL\xerces.jarCLASSP
  ATH
• cd XSL
• java org.apache.xalan.xslt.Process IN ltxmlgt -XSL
  ltXSLTgt -OUT ltOUTgt -ltFORMATgt

15
Stylesheet Element

• XSL is a well-formed XML document
• The tree of the source document
• The tree of the resulting document
• How to transform one into the other
• Top element of XSLT
• ltxslstylesheet version"1.0 xmlnsxslhttp//ww
  w.w3.org/1999/XSL/Transform xmlnshttp//www.w3.o
  rg/TR/REC-html40gt

16
Template Elements

• Example
• ltxsltemplate match"section/title"gt
  ltPgtltIgtltxslapply-templates/gtlt/Igtlt/Pgtlt/xsltemplat
  egt
• A template has two parts
• The match attribute a path to the element in the
  source tree to which the template applies
• The content list the elements to insert in the
  resulting tree

17
Path

• XML path is similar to file paths
• Start from the root of an XML document
• Elements are separated by /
• The root is a node before the top-level element
• Path Tips
• / immediate children of a node
• /article/title
• // all the descendant from a node
• /article//title
• wildcard character (/article/)
• or character (title p)

18
Path Example
root
/
/article
article
title
date
abstract
keyword
section
/article/title
19
Compute the Value of a Node

• xslvalue-of takes the value of something and
  copies it into the output document
• ltxsltemplate matchATOMgt ltxslvalue-of
  selectNAME /gtlt/xsltemplategt
• select is relative to the current node
• The value of a node is always a string
• Value of an element node concatenation of all
  the parsed character data (but not markup)
  between its start and end tag

20
Matching on Attributes

• Syntax
• matchelement_at_attributevalue
• matchurl_at_protocolmailto
• lturl protocolmailtogt claven_at_cc.nctu lt/urlgt
• lturl protocolhttpgt http//. lt/urlgt
• matchelement_at_attribute
• matchurl_at_protocol
• lturl protocolhttpgt http//. lt/urlgt
• lturlgthttp//www.w3.org lt/urlgt

21
Matching Text and Functions (I)

• Functions restrict paths to specific elements
• /article/sectionposition()2/title/text()
• /article/section2/title/text()
• count(//title)

22
Matching Text and Functions (II) -- Common XSL
functions

• position()
• the position of the current node in the node set
• text()
• The text (content) of an element
• last()
• the position of the last node in the current node
  set
• count()
• the no of nodes in the current node set
• not()
• negates the argument
• contains()
• return true if the first argument contains the
  second argument
• starts-with()
• return true if the first argument starts with the
  second argument

23
Actions of XSL Processor

• Load the style sheet
• Load the source document
• Walk through the source document from root to
  leaf
• Match the current node against a template
• If match, generates the node in the resulting
  tree
• Encounter ltxslapply-templatesgt
• Move to the children of the current node and
  repeat the process

Recursive call to the Stylesheet
24
Built-in Template

• ltxsltemplate match / gtltxslapply-template
  s /gtlt/xsltemplategt
• ltxsltemplate match"text()_at_"gt ltxslvalue-of
  select"."/gtlt/xsltemplategt
• ltxsltemplate match"processing-instruction()comm
  ent()"/gt

25
Creating Nodes in the Resulting Tree (I)

• xslelement
• creates element with a computed name
• xslattribute
• creates attribute with a computed value
• xslattribute-set
• Conveniently combines several xslattribute
• xsltext
• Create a text node
• xslprocessing-instruction
• Create a processing instruction

26
Creating Nodes in the Resulting Tree (II)

• xslcomment
• create a comment
• xslcopy
• copies the current node
• xslvalue-of
• computes text by extracting from the source tree
  or inserting a variable
• xslif
• instantiates its content if the expression if
  true
• xslchoose
• select elements to instantiate among possible
  alternatives
• xslnumber
• creates formatted number

27
Priority

• Templates with more specific paths take
  precedence over less specific templates
• If conflict between two templates of equivalent
  priority
• Report an error
• Choose the template that appears last in the
  style sheet

28
Customized View
XSL Processor
29
Where to Apply the Stylesheet
30
XSL and IE 5.0

• Associate a style sheet with the current document
• lt? xml-stylesheet href.. typetext/xsl ?gt
• Changes to the stylesheet
• Namespace Change
• ltxslstylesheet xmlnsxslhttp//www.w3.org/TR/W
  D-xsl xmlnshttp//www.w3.org/TR/REC-html40gt
• IE has no built-in templates
• Must declared explicitly

31
Advanced XSLT
32
Declaring HTML Entities in a Style Sheet

• lt!DOCTYPE xslstylesheet lt!ENTITY copy
  0169gt gt

33
Reorganizing the Source Tree

• ltMETA NAME"keywords"gt ltxslattribute
  name"CONTENT"gt ltxslvalue-of
  select"article/keywords"/gt, lt/xslattributegtlt/
  METAgt
• ltMETA NAMEkeywords contentXML, XSL, style
  sheet, publishing, Webgt

34
Calling a Template

• Template define with a name
• ltxsltemplate name"title"gt ltxslvalue-of
  select"/article/title"/gt (
• ltxslvalue-of select"/article/date"/gt )
• lt/xsltemplategt
• Call a template
• ltxslcall-template nametitle /gt

35
Include a Style Sheet

• ltxslinclude hrefcore.xsl /gt
• xslinclude must be a direct child of
  xslstylesheet

36
Repetitions

• ltxslfor-each select"article/section/title"gtltLIgt
  ltAgtltxslattribute name"HREF"gt ltxslvalue-of
  select " generate-id()"/gtlt/xslattributegtltxslv
  alue-of select"."/gtlt/Agtlt/LIgtlt/xslfor-eachgt
• xslfor-each loop over elements
• generate-id() Return a unique identifier for the
  current node