learning xslt

Learning XSLT

A Tutorial

Mike Fitzgerald

Wy’east Communications

15 November 2004 Slide 2

Quick Start: What Is XSLT?

Extensible Stylesheet Language or XSLT XML Path Language or XPath is a

companion specification to XSLT Both recommendations published by the

World Wide Web Consortium (W3C) inNovember 1999


Quick Start: Templates

XSLT stylesheets are driven by templates Documents processed on a template model Templates can have: (1) innate priority or (2)

assigned assigned priority (rare) Templates can have modes Can name templates, pass them parameters Built-in templates Attribute value templates


Quick Start: XPath

XPath is a non-XML syntax for addressing nodes with location paths

XPath data model describes XML documents with seven node types

Types are root (document in 2.0), element, attribute, text, namespace, comment, processing instruction


Quick Start: More XPath

Expressions in attribute values Patterns, subset of expressions Predicates, method for filtering nodes Axes, forward and reverse Arithmetic in expressions Functions in expressions (XSLT adds

functions XPath set of functions)


Quick Start: Output

Output methods: text, XML, or HTML (XHTML in 2.0)

Literal result elements Instruction elements Control over things like indentation, XML

declarations, document type declarations, media types, and more


Quick Start: Processing

Several methods of copying nodes across Variables and parameters Can pass parameters in from outside

stylesheet, and outside a template Can process nodes conditionally Sorting and numbering of lists


Quick Start: Keys

Keys are mainly a performance hike You can use more than one key You can use parameters with keys You can cross-reference with keys


Quick Start: Multiple Documents

Multiple stylesheets through inclusion Multiple stylesheets through importation Multiple source documents Multiple output documents (through

extension in 1.0, standard in 2.0)


Quick Start: Alternative Stylesheets

Normal stylesheets Literal result stylesheets Embedding stylesheets Namespace aliasing Namespace exclusion


Quick Start: Extensions

XSLT designed for extension Can use processor-specific extensions, such

as those from Xalan, Saxon, EXSLT Can extend XSLT yourself XSLT 2.0 provides a native way to write

extension functions in XML syntax


Main Presentation

A brief introduction to XSLT and XPath Focus on version 1.0, with asides to 2.0 Most features covered, though not all Basic understanding of XML assumed Example files available on CD (in DOS

format, so use conv –U for Unix line endings)


W3C Specifications

XSLT 1.0 specification http://www.w3.org/TR/xslt

XPath 1.0 specification http://www.w3.org/TR/xpath

Working drafts of version 2.0 editions http://www.w3.org/TR/xslt20 http://www.w3.org/TR/xpath20


What Is XSL-FO?

Originally, XSLT was included in Extensible Stylesheet Language or XSL

XSL deals with appearance, formatting XSL is commonly called XSL-FO Specs parted company in April 1999


What Does XSLT Do?

A language in XML syntax that defines and describes transformations

Transforms XML to: XML HTML XHTML (2.0) plain text


From Source to Result

Source XML document becomes source tree Source document could be a file or a stream Result document could be a file or stream A result tree can be serialized as an XML,

XHTML, HTML, or text document Text documents could be C++, Java, Python,

SQL, or what have you


Process Flow

SourceStyle-sheet

Result

Processor Inputs

Processor Output


Templates

The template is the heart of XSLT Templates match patterns in source trees A pattern is generally a location in the

structure of the source tree A template is invoked to search for a pattern A template that finds a pattern can be

instantiated and create a result tree for output


Stylesheet Basics

A document element in XSLT can be stylesheet or transform

version is required attribute Namespace declaration is required

http://www.w3.org/1999/XSL/Transform

Conventional prefix is xsl


ch01/msg.xml & ch01/msg.xsl

ch01/msg.xml just an empty document element

ch01/msg.xsl, document element is stylesheet, version attribute, namespace

Top-level element output, and method attribute with value of text

Top-level element template matches the pattern msg using the match attribute

Literal result text Found it!


Some XSLT Processors

Instant Saxon (http://saxon.sourceforge.net)

saxon msg.xml msg.xsl

Saxon (http://saxon.sourceforge.net):java –jar saxon7.jar msg.xml msg.xsl

Xalan C++ (http://xml.apache.org):

xalan msg.xml msg.xsl

XRay (http://www.architag.com) xmlspy (http://www.xmlspy.com)


A Simple Transformation

Transform the document with the stylesheet:

xalan msg.xml msg.xsl Yields this result:

Found it! How did that happen?


ch01/msg-pi.xml

An XML stylesheet processing instruction is similar to the HTML element LINK

Points to a stylesheet:<?xml-stylesheet href="msg.xsl" type="text/xsl"?>

Some processors accept text/xslt A W3C specification:http://www.w3.org/TR/xml-stylesheet


XSLT & Browsers

Several browsers support client-side XSLT transformations, such as IE 6.0, Netscape 7.1, Mozilla 1.7, Firebird 0.9

Load ch01/msg-pi.xml in a browser See the results in that browser


ch01/message.xml

XML declaration with version information An XML declaration is not a processing

instruction Document element message Attribute priority with value low Text content (#PCDATA in DTD terms)


value-of Instruction Element

Children of top-level elements are usually instruction elements

value-of’s required select attribute Returns a string value


ch01/message.xsl

stylesheet element with version and namespace

output element, method is text template matches message value-of selects text content of message

text() is a node test for text nodes


Another Transformation

Transform the document with the stylesheet:

xalan message.xml message.xsl Yields this result:

Hey, XSLT isn’t so hard after all!

What happened?


Applying Templates

Templates processes children of the matched node

The apply-templates finds other templates that match those children

The select attribute of apply-templates finds a specific template that matches a child


XPath 1.0 Data Model

XPath sees XML documents as a set of one or more nodes of seven types:

1. Root (or document in 2.0)

2. Element

3. Attribute

4. Text

5. Namespace

6. Comment

7. Processing instruction


ch04/nodes.xml via ch04/tree-view.xsl


Root Node

The root node is the root of the XML document

Called the document node in XPath 2.0 Has at most one element node child, that is,

the root or document element Location path: /


Element Nodes

Elements are the building blocks of structured XML documents

A location path: message/body/line All elements: * All elements of a given namespace (name

test): rng:*


Attribute Nodes

Attributes effectively modify elements Location path: message/@priority All attributes: @* xmlns, with or without a prefix (as in xmlns:rng), is not treated as an normal attribute


Other Nodes

Match text nodes with text() node test Match namespace nodes with namespace::*

axis or namespace-uri() function Match comments with comment() node test Match processing instructions with processing-instruction() node test


Built-in Template Rules

Hidden magic that is sometimes confusing Automatically kick in when an explicit

matching template is not found, but a node matching the built-in template is present

In absence of appropriate templates, built-in templates are used


Built-in Templates...

Match patterns Match the root node and all element nodes,

including modes Match text and attributes No-ops on comments, processing

instructions, namespace nodes Try ch10/built-in.xsl


Template Rules

Templates have priority when more than one template matches the same node

The template element has a priority attribute which takes a real number

Stylesheets can be included and imported Imported templates are governed by import

precedence rules


Literal Result Elements

You can literally add text, elements, and attributes to a result tree

Can use attribute value templates ({}) in the attribute values of literal result elements

Namespaces apply to literal result elements Markup in stylesheet subject to well-

formedness constraints


Literal Examples

Examples from ch02... Literal text:

xalan text.xml txt.xsl Literal result element:

xalan literal.xml literal.xsl Literal HTML markup:

xalan literal.xml html.xsl Literal XHTML markup (with 1.0):

xalan doc.xml doc.xsl


Instruction Elements

element creates an element attribute creates an attribute attribute-set creates a reusable set of

attributes (top-level element) text creates text comment creates comments processing-instruction creates a

PI


ch02/final.xsl

attribute-set is a top-level element that can contain zero or more attribute elements

processing-instruction creates an XML stylesheet PI for a CSS document

comment adds a comment to the document prolog before document element


More on ch02/final.xsl

Literal result elements element creates elements attribute value is derived the from

source using an absolute location path text element adds some text to the result

without adding unintended whitespace


output Element

Top-level element (zero or more) Controls output methods: xml, html, text or a QName (qualified name)

xhtml method available in XSLT 2.0 Structural indentation with the indent

attribute (yes or no) encoding attribute has values such asUS-ASCII, UTF-8, or ISO-8859-1


XML Declaration & output

omit-xml-declaration attribute (yes or no)

version attribute sets version information standalone attribute sets standalone

declaration (yes or no)


More on output

media-type attribute sets media type as in text/xml or application/xml

cdata-section-elements sets result tree elements that contain CDATA sections

doctype-system and doctype-public output document type declarations using SYSTEM or PUBLIC identifiers

See examples in ch03


Expressions

Defined by XPath Expressions in select attributes Expressions can contain:

patterns (next slide) boolean and relational logic (and, or, !=, >) arithmetic (+, -, *, /, mod) functions (name(), last(), count()) variable references ($var)


Patterns

Defined by XSLT as subset of an expression Patterns most often in match attributes Patterns often contain:

location steps (date/year) / (root) or // (descendant) or | (union) Node test (*, rng:*, comment(), text()) id() or key() functions child:: or attribute:: axes Predicate (state/name[.='Oregon'])


Axes

Abbreviated and unabbreviated syntax Double colon separator (attribute::priority) Forward or reverse axes:

Forward: attribute, child, descendant, descendant-or-self, following, following-sibling, namespace, parent, self

Reverse: ancestor, ancestor-or-self, preceding, and preceding-sibling



Functions

Part of expressions, so always called in attribute values that contain expressions (usually select)

Node-set, number, boolean, string functions XPath functions examples: position(), concat(), not(), sum()

XSLT function examples: document(), current(), key(), format-number()



Copying Nodes

Shallow copy versus deep copy copy element performs a shallow copy:

element nodes and namespace nodes copy-of element performs deep copy:

element and child nodes, attribute nodes, namespace nodes



Variables & Parameters

variable and param elements, both top-level or instruction elements

Referenceable value ($var) with scope Can’t change variable value Result tree fragment or temporary tree in

XSLT 2.0 (see with extensions) See examples in ch07


More on Variables & Parameters

param value can change, have default Can pass parameters to a stylesheet Can pass parameters to a template using with-param


Sorting Nodes

The sort element sorts nodes Child of apply-templates or for-each

Ascending or descending Alphabetical or numerical If alphabetical, by uppercase or lowercase See examples in ch08


Numbering Nodes

The number element inserts formatted numbers into result tree as for a list

Numerical, alphabetical, Roman numerals Used with format-number() function Also used with decimal-format top-

level element See examples in ch09


Named Templates

A template element can have a name attribute Can have match and name attributes together,

but if no match, must have name Can call templates by name with the call-template element, with parameters (with-param)

Displaced by XSLT 2.0 element function See examples in ch10


Modes

Can’t apply template that matches a given node more than once

Overcome by modes Matching mode attribute on template

and apply-templates


Keys

Can match nodes based on a key value Define keys at the top-level using the key

element Later called using the key() function in

patterns or expressions See examples in ch11


Conditional Processing

Test a single condition with an expression using an if instruction element

Test multiple conditions with expressions using when instruction elements in choose (if-then statement)

choose can contain optional otherwise element (if-then-else statement)



Including Stylesheets

Can include external stylesheet(s) with include element

Include effectively merges stylesheets See examples in ch13


Importing Stylesheets

Can also import external stylesheet(s) with import element

Import builds import tree with precedence based on sequence of imports

apply-imports can trump normal precedence



Alternative Stylesheets

Literal result element stylesheet uses a literal result element as the document element

Embedded stylesheets allow you to combine source tree and stylesheet into one document by using a fragment identifier with an id attribute



Extensions

XSLT 1.0 can’t satisfy everyone, so extensions possible

Can write namespace-qualified extension elements, functions, and attributes

Can define your own extensions or use extensions already defined

Can define fallback behavior using fallback and message elements



XSLT 2.0 Highlights

xhtml output method Multiple result trees (result-document) Regular expressions (analyze-string) Define stylesheet functions (function) Validation with XML Schema Format dates (date-format, format-date()) Grouping (for-each-group) Character maps (character-map, output-character)


XPath 2.0 Highlights

Many new functions (177 versus 27) Strongly typed, relying on XML Schema

datatypes Kind tests (document-node(), element(), attribute())

Casting (cast, castable) for and if statements in expressions See examples in ch16


Ox Documentation Tool

Syntax-related XSLT documentation on the command line

XML vocabulary items, too Example:

java –jar ox.jar xsl:text

See: http://www.wyeast.net/ox.html


So Long and Thanks!

Mike Fitzgerald

Wy’east Communications

learning xslt

Technology

templates xslt stylesheets

source xml document

expressions xslt

xml documents

xslt browsers

extensions xslt

xslt transformations

quick start