1. Introduction to XSLT Justin Tilton instructional media + magic, inc.
As presented at the JA-SIG Winter Conference: "All Java, All the Time"
December 8th 2002, Orlando, Florida

2. The Abstract…
Looking for a methodology to quickly and effectively create Transformations? Interested in the basics of XSLT and Xpath, and a good way to get started? If so, this workshop is for you! We will be discussing the fundamental concepts of XSLT and Xpath, and the methodologies that have emerged from months of developing stylesheet transformations for the uPortal 2.0 project.
We will discuss the design aspects related to converting structured information in XML into device-dependent markup languages such as HTML, and WML, and the guidelines and best practices evolving from this experience. No prior XSLT experience is necessary.

3. Overview Introduction uPortal Basic XPath Basic XSLT Markup: XHTML
Cascading Style Sheets
Tools
The Creation Process
Hands-on

4. Introduction

5. Background Who: W3C What: XPath and XSLT Specs. When: 11/16/1999
Why: A need arose for a specification to define the syntax and semantics for transforming XML documents.

6. References “The” definitive reference… Michael Kay Wrox Press Inc
ISBN:

7. References Great practical reference… Jeni Tennison Hungry Minds
ISBN:

8. References Practical use of transformations in Java code Eric Burke
O'Reilly & Assoc.
ISBN:

9. JA-SIG’s uPortal

10. What’s new in 2.x? Abstraction of layout
Structure/theme transformations
Standard channel events
Standard CSS classes
More flexible publish/subscribe
User profile management
Groups and Permissions updates

11. Basic Architecture
Framework
Structure XSLT
Theme XSLT
Skins - CSS

12. Basic Architecture Permissions authentication User preferences
iPlanet
LDAP
authentication
User preferences
Channel registry
Other uPortal Data
Oracle db2
mySQL

13. Channel
Elementary unit of presentation, defined by the IChannel interface
User Interaction External Information
Channel Content (Presentation)
IChannel

14. IChannel content must
Be well-formed XML such as XHTML, RSS, SVG, SMIL, or a SOAP message (HTML is not well formed XML)
Rendered by an XSL transformation using an XSL stylesheet

15. Framework Organization
User Interaction
Presentation
uPortal Framework
Channel
Channel
Channel

16. User Layout
User Layout is an abstract structure defining the overall content available to the user
userLayout is a tree structure consisting of “folders” and “channels”, the later always being the leaf nodes

17. User Layout

18. Structure Transformation
Channel
Column
Tab
User Layout

19. Theme Transformation User Layout Tab Tab Tab Jim Smith Financial Aid
Library
Column
Column
Channel
Channel
Channel
Channel
Channel
Channel
Dictionary.com
Bookmarks
Cartoon

20. Compiling the Presentation
userLayout
Structure transformation
XSLT
structuredLayout
setRuntimeData()
XSLT
Channels
Theme transformation
renderXML()
HTML, WML VoiceML...

21. Content Transformation
XML
XSLT
Processor
XHTML: Web Browser
HTML: PDA
Stylesheet
WML: Cell Phone

22. Flexible Layouts Structures Themes Skins Tab / column Tree / column
Multi-column
Multi-row
Skins
Matrix, Java

23. Multiple Target Devices

24. Tab / Column Layout

25. Tree / Column Layout

26. Skins

27. Skin: im+m

28. Skin: VSAC

29. Skin: matrix

30. User Preferences Swappable layout and preference management modules
Profile management module
Tab-column specific prefs. module
Skin selection

31. User Preferences

32. Publish/Subscribe Channel publishing document
Channel parameters
Default values
Modification permissions
Descriptions
Publish/Subscribe steps
Step sequence
Instructions, help
A complex channel with multiple XSL views

33. Channel Types

34. Channel Settings

35. Channel Controls

36. Channel Rewiew

37. Basic XPath

38. Nodes and Node Trees
When an application wants to operate on an XML document it builds an internal model of what the document looks like.
This model is known as a document object model or DOM.
In XPath and XSLT, it's called a node tree.

39. Types of Nodes Root nodes Element nodes Attribute nodes Text nodes
The top of the node tree
Element nodes
XML elements
Attribute nodes
XML attributes
Text nodes
Textual content in XML elements
Comment nodes
XML comments
Processing instruction nodes
XML processing instructions
Namespace nodes
The in-scope namespaces on an element R E E E E A T

40. Node Tree Example <document> </document>
<para type=“note”> content </para>
<para type=“warning”> content </para>
</document>
document
para
warning
note
content

41. XPath Definition
XPath is a language for addressing parts of an XML document, designed to be used by XSLT.
Example XPath:
child::para[attribute::type='warning'][position()=2]
In English:
select the second para child of the context node that has a type attribute with a value of warning.

42. Dissecting the Example
child::para[attribute::type='warning'][position()=2]
Axis: child::para
Filter: [attribute::type='warning']
Filter: [position()=2]
Context node
Axis

43. Dissecting the Example
child::para[attribute::type='warning'][position()=2]
Axis: child::para
Filter: [attribute::type='warning']
Filter: [position()=2]
Context node
Axis
Filtered

44. Dissecting the Example
child::para[attribute::type='warning'][position()=2]
Axis: child::para
Filter: [attribute::type='warning']
Filter: [position()=2]
Context node
Axis
Filtered
Filtered

45. Dissecting the Example
child::para[attribute::type='warning'][position()=2]
Axis: child::para
Filter: [attribute::type='warning']
Filter: [position()=2]
Context node
Axis
Filtered
Filtered
Selected

46. Types of XPaths Expressions: Patterns:
Return a value, which might be a node set that is processed or a string that is output.
<xsl:when
Patterns:
Either match a particular node or don't match that node.
<xsl:template match="para">

47. XPath Expressions Select Nodes Conditional Calculation C Z Z C 1 2 3 4
<xsl:for-each select=“child::Z”>
Conditional
<xsl:if test=“position()=2”>
Calculation
<xsl:value-of select=“position()+4"> C Z Z C 1 2 3 4

48. Node Set Expressions
The most common way that XSLT uses XPaths is to select node sets. These XPaths usually occur within a select attribute, for example on xsl:for–each or xsl:apply–templates, and are known as location paths.
<xsl:for-each select=“child::para”>
<xsl:apply-templates select="paragraph"/>

49. Location Paths
The purpose of location paths is to select node sets from a node tree.
Location paths can be absolute or relative
Absolute location paths start from a known location such as the root node
<xsl:for-each select=“/R/N”>
Relative location paths start from the context node.
<xsl:for-each select=“N”> note: same as “child::N” R N X Y N R N X Y
C ontext N Z

50. Steps A location path is made up of a number of steps.
Each step takes you from a node to a node set.
Each step is separated from the one before it with a “/”.

51. Steps Every step is made up of an axis and a node test.
The axis specifies the direction that the step is taken in
The node test specifies the kinds of nodes that should be collected in that direction.
Within a step, the axis and the node test are separated by a double colon “::”.
“ child :: para ”

52. Some Shorthand Notation
If no axis is specified in a step, the default axis is the child axis.
Longhand select=“child::para/child::sentence”
Shorthand select=“para/sentence”
Another important axis is the attribute axis, which takes you from the context node to the attributes of that node.
Longhand select=“attribute::type”
Shorthand
Another essential axis is the parent axis. This takes you from the context node to the parent of that node.
Longhand select=“parent::node()/child::xyz”
Shorthand select=“../xyz”

53. Axes ancestor :: node()
Takes you up the tree to the ancestors of the context node in reverse document order. 2 1

54. Axes ancestor-or-self :: node()
Takes you up the tree to the ancestors of the context node in reverse document order starting with the context node. 3 2 1

55. Axes
child :: node()
Takes you to the children of the context node in document order. This is the default axis. 1 2

56. Axes descendant :: node()
Takes you to the descendants of the context node. The resulting nodes are in document order. 1 3 2 4 5 6

57. Axes descendant-or-self :: node()
Takes you to the descendants of the context node, starting with the context node, in document order. 1 2 4 3 5 6 7

58. Axes following :: node()
Takes you to the nodes that occur after the context node in document order, but that are not the context node’s descendants. 1 4 2 3

59. Axes following-sibling :: node()
Takes you to the siblings of the context node that occur after the context node in document order. 1 2

60. Axes
parent :: node()
Selects a single node – the parent of the context node. 1

61. Axes preceding :: node()
Takes you to the nodes that occur before the context node in reverse document order, excluding the context node’s ancestors. 3 2 1

62. Axes preceding-sibling :: node()
Takes you to the siblings (children of the same parent) of the context node that occur before it, in reverse document order. 2 1

63. Axes
self :: node()
Takes you to the context node itself. 1

64. Predicates (filters) Predicates are placed in square brackets either:
at the end of a step
select=“para[position()=3]/sentence”
or at the end of a location path
select=“para/sentence[position()=3]”
Predicates act as filters on node sets.
When predicate expressions test false, the node is filtered out.

65. Predicates (filters)
You can have any number of predicates following each other.
The context node list for each predicate contains the nodes that are still in the node set after it's been filtered by the previous predicates.
Predicates can be used at any point in a location path, but they only apply to the immediately preceding step.

66. Expressions - Union
You can combine node sets by creating a union using the “|” operator.
If there are any nodes that occur in both node sets, the union only holds one copy of them.
You can use predicates on the result of a union, just as you can on any node set.

67. Expressions - Operators
Logical Operators
and, or and not()
Comparative Operators
=, !=, <, <=, >, >=
Remember to escape: “<“ to <
Mathematical Operators
+, -, *, div, mod

68. XPath Examples select=“presidents/president/[position()=3]/name”
select=“//president[count(vicePresident)=0]/name”
< 1800]/name”
select=“descendant::president/ [count(vicePresident)>1]/name”
select=“//president/name[child::first=‘John’]”
> 1800) and < 1850)/name”

69. Basic XSLT

70. Background
XSLT is part of a larger initiative within the World Wide Web Consortium (W3C) to define a way of presenting XML documents. This initiative is known as XSL (Extensible Stylesheet Language).
XSLT is an XML vocabulary that's used to define a transformation between an XML document and a result document, which might be in XML, in HTML, or a text document.

71. What is an XSLT Stylesheet?
The XSLT processor uses a stylesheet to transform an XML document.
The stylesheet contains instructions for generating a new document based on information in the source document.
This can involve adding, removing, or rearranging nodes, as well as presenting the nodes in a new way.

72. The XSL Processing sequence
source document
XML parser
source tree
XSL stylesheet
rules base
apply
templates
Result file
or stream
write result
to output
result tree

73. Differentiating Stylesheets
XSLT stylesheets do not perform the same function as Cascading Style Sheets (CSS)
CSS is used to apply style elements to markup languages to affect formatting in a single pass, top down, fashion.
XSLT produces a separate result tree and can iterate and perform conditional logic.
XSLT and CSS are most powerful when used together. More later…

74. Example of a Stylesheet
When you work with a stylesheet, three documents are involved:
Source document in XML
Desired output: the result document, which can be HTML, XML, or text
XSLT stylesheet, which is also an XML document

75. “Hello World!” XML Document: Desired Output: XSLT Stylesheet: root
<?xml version="1.0"?>
<greeting>Hello, World!</greeting>
Desired Output:
<html>
<head><title>Greeting</title></head>
<body><p>Hello, World!</p></body>
</html>
XSLT Stylesheet:
<xsl:stylesheet version="1.0" xmlns:xsl="
<xsl:template match="/">
<body><p><xsl:value-of select="greeting"/></p></body>
</xsl:template>
</xsl:stylesheet>
root
greeting
Hello World!

76. Dissecting the XSLT XSLT stylesheets are XML Documents
<?xml version="1.0"?>
Standard XSLT heading/Namespace
<xsl:stylesheet version="1.0" xmlns:xsl="
The template rule to be triggered when a particular part of the source document is being processed. “/” is XPath for “root node”
<xsl:template match="/">

77. Dissecting the XSLT
Once the rule is triggered the body of the template defines what output to generate.
<html>
<head><title>Greeting</title></head>
<body><p><xsl:value-of select="greeting"/></p></body>
</html>
Most of the template is HTML except the value-of element which is an XSL instruction.
The XPath in the select statement is asking for the contents of the child of the context node with an element name of greeting.
root
greeting
Hello World!

78. Dissecting the XSLT
All that’s left to do is close (finish) the template and the stylesheet.
</xsl:template>
</xsl:stylesheet>

79. Some XSL Top Level Elements
<xsl:decimal-format>
Declares a decimal format.
<xsl:import>
Imports another stylesheet into this stylesheet.
<xsl:key>
provides a way to work with documents that contain an implicit cross-reference structure
<xsl:output>
This instruction specifies how you want the result tree to be output

80. Some XSL Top Level Elements
<xsl:param>
Declares a parameter for a stylesheet or template, and specifies a default value for the parameter
<xsl:template>
Specifies a template rule.
<xsl:variable>
Declares a variable and binds a value to that variable.
The difference between the xsl:param and xsl:variable instructions is that xsl:param defines a default value while xsl:variable defines a fixed value.
If used as a top level element the scope is global otherwise the scope is local to a specific template

81. What Is a Template?
A template defines what the XSLT processor should do when it processes a particular node in the XML source document.
The XSLT processor populates the result document by instantiating a sequence of templates.
Instantiation of a template means that the XSLT processor
Copies any literal data from the template to the result document
Executes the XSLT instructions in the template

82. Contents of a Template
To define a template, you specify the xsl:template instruction.
In the xsl:template tag, the value of the match attribute is an XPath pattern.
This pattern matches (identifies) nodes in the source XML document.
The value of the match attribute is the template rule.

83. The Template Body
The template body defines actions you want the XSLT processor to perform each time it instantiates the template. It contains
XSLT instructions you want the XSLT processor to follow
Elements that specify literal output you want the XSLT processor to insert in the result document. For example:
<table align="center" cellpadding="5">

84. Determining Templates to Instantiate
When the XSLT processor applies a stylesheet to an XML document, it begins processing with the root node of the XML source document
Every stylesheet includes default templates
Whether or not you explicitly define a template rule that matches the root node, the XSLT processor always instantiates a template that matches the root node.

85. The Example Handout

86. Dissected XSLT Stylesheet

87. Result

88. Dissecting a sample
In the sample stylesheet, the template rule in the first template matches the root node:
<xsl:template match="/">
The XSLT processor instantiates this template to start generating the result document.
It copies the first few lines from the template to the result document.

89. Dissecting a sample
Then the XSLT processor reaches the following XSLT instruction:
<xsl:apply-templates select="/bookstore/book"/>
When the XSLT processor reaches the select attribute, it creates a list of all source nodes that match the specified pattern.
In this example, the list contains book elements.
The processor then processes each node in the list in turn by instantiating its matching template.

90. Dissecting a sample
First, the XSLT processor searches for a template that matches the first book element. The template rule in the second template matches the book element:
<xsl:template match="book">
After instantiating this template for the first book element, the XSLT processor searches for a template that matches the second book element…

91. Dissecting a sample
The XSLT processor instantiates the book template again, and then repeats the process for the third book element.
After three instantiations of the book template, the XSLT processor returns to the first template (the template that matches the root node) and continues with the line after the xsl:apply-templates instruction.

92. Built-in Templates
When the XSLT processor cannot find a template that matches a selected node, it uses built-in templates. Every stylesheet includes built-in templates whether or not you explicitly define them.

93. Built-in Templates
The following template matches the root node and element nodes and selects all attributes and child nodes for further processing:
<xsl:template match="*|/">
<xsl:apply-templates / >
</xsl:template>
The following template matches text and attribute nodes. This template copies the value of the text or attribute node to the result document:
<xsl:template
<xsl:value-of select="." / >

94. Major XSL Instructions
xsl:apply-imports
xsl:apply-templates
xsl:attribute
xsl:attribute-set
xsl:call-template
xsl:choose
xsl:comment
xsl:copy
xsl:copy-of
xsl:decimal-format
xsl:element
xsl:fallback
xsl:for-each
xsl:if
xsl:import
xsl:include
xsl:key
xsl:message
xsl:namespace-alias
xsl:number
xsl:otherwise
xsl:output
xsl:param
xsl:preserve-space
xsl:processing-instruction
xsl:sort
xsl:strip-space
xsl:stylesheet
xsl:template
xsl:text
xsl:transform
xsl:value-of
xsl:variable
xsl:when
xsl:with-param

95. XHTML

96. Why XHTML? XSLT Stylesheets are XML documents
If you plan to output HTML, it will reside in the template bodies of the XSLT Stylesheet, and the markup will be output as literal output.
When the XSLT Stylesheet contains Markup, it has to be well formed

97. Differences with HTML 4
Due to the fact that XHTML is an XML application, certain practices that were perfectly legal in HTML 4 must be changed.
Documents must be well-formed
Well-formedness is a new concept introduced by [XML]. Essentially this means that all elements must either have closing tags or be written in a special form (as described below), and that all the elements must nest.
CORRECT: nested elements.
<p>here is an emphasized <em>paragraph</em>.</p>
INCORRECT: overlapping elements
<p>here is an emphasized <em>paragraph.</p></em>

98. Differences with HTML 4
Element and attribute names must be in lower case
XHTML documents must use lower case for all HTML element and attribute names. This difference is necessary because XML is case-sensitive e.g. <li> and <LI> are different tags.

99. Differences with HTML 4
In HTML 4 certain elements were permitted to omit the end tag; with the elements that followed implying closure. This omission is not permitted in XML-based XHTML. All elements must have an end tag.
CORRECT: terminated elements
<p>here is a paragraph.</p> <p>here is another paragraph.</p>
INCORRECT: unterminated elements
<p>here is a paragraph. <p>here is another paragraph.

100. Differences with HTML 4
All attribute values must be quoted, even those which appear to be numeric.
CORRECT: quoted attribute values
<table rows="3">
INCORRECT: unquoted attribute values
<table rows=3>

101. Differences with HTML 4
XML does not support attribute minimization. Attribute-value pairs must be written in full. Attribute names such as nowrap and checked cannot occur in elements without their value being specified.
CORRECT: unminimized attributes
<td nowrap=“nowrap">
INCORRECT: minimized attributes
<td nowrap>

102. Differences with HTML 4
Empty elements must either have an end tag or the start tag must end with />. For instance, <br/> or <hr></hr>.
CORRECT: terminated empty tags
<br/><hr/>
INCORRECT: unterminated empty tags
<br><hr>

103. Cascading Style Sheets

104. CSS uPortal and Skins
uPortal uses Cascading Style Sheets to “Skin” the portal and content.
These CSS files are optimized for a particular structure.
For consistency channel developers should become familiar with the CSS classes that are defined for a particular structure and apply them to the markup language in their XSLT transformations.

105. The CSS Classes
There is a sample “developer” channel in uPortal that describes and gives examples of the CSS classes for the Tab/Column Theme.

106. The CSS Channel

107. The Tools

108. The Applications…
These are the applications I am familiar with -- this is not an endorsement  -- and no testing was done on animals…
XML/XSLT Document Development IDE:
Excelon Stylus Studio
XML Spy
Cooktop (open source)
Komodo (commercial – runs on LINUX)
Emacs (minor mode XSLT-process)
HTML Markup IDE:
Macromedia Dreamweaver MX (XHTML), Adobe GoLive
HTML to XHTML Conversion/Cleanup
HTML Tidy (open source)

109. The Creation Process

110. Creating an XSLT Stylesheet
Step One – get or develop one of the following:
A representative XML Document
A DTD (a whole different seminar)
A Schema (a whole different seminar)
Step two – Analyze the data
Think about the best way to present and interact with it. The data is your friend.
Step three – Develop sample markup
Design mocks for each markup language & device that you plan to support. Don’t try to paint the canvas without a sketch.
Step four – Convert the markup to XML
The stylesheet will only eat tasty markup. Poorly formed markup will be regurgitated.
Step five – copy markup into XSLT editor
Match on a root element and start cooking XSLT.

111. Hands - on

112. Hands – on
Convert RSS (Rich Site Summary) “Syndicated Content” XML Documents into HTML using an XSLT Stylesheet.