+ xsl extensible stylesheet language. + 2 xml lecture adapted from the work of prof mark baker acet,...

+

XSL

eXtensible Stylesheet Language

2+XML Lecture

Adapted from the work of Prof Mark Baker ACET, University of Reading

+Outline

Basic Overview.

Applying XLST Stylesheets.

Using a XSL Processor.

Example XSL - generating HTML.

Creating a Stylesheet,

Template rules

Patterns.

Some XSL Syntax.

Summary.

+XSL

XSL is a family of recommendations for defining XML document transformation and presentation.

It consists of three parts: XSL Transformations (XSLT) a language for transforming XML, The XML Path Language (XPath), an expression language used by

XSLT to access or refer to parts of an XML document. XSL Formatting Objects (XSL-FO) an XML vocabulary for specifying

formatting semantics.

An XSLT stylesheet specifies the presentation of a class of XML documents by describing how an instance of the class is transformed into an XML document that uses a formatting vocabulary, such as (X)HTML or XSL-FO.

+XSL (eXtensible Stylesheet Language) XSL is a high-level functional language used to transform XML documents into various formats, e.g. XML, HTML etc..

An XSL program consists of a set of TEMPLATE rules.

Each rule consists of a pattern and a template: The XSL processor starts from the root element and tries to

apply a pattern to that node; If it succeeds, it executes the corresponding template.

The template, when executed, usually instructs the processor to produce some XML result and to apply the templates,

Recursively on the node's children.

An XSL style sheet is a valid XML document

+<?xml version="1.0" encoding="ISO-8859-1"?><catalog> <cd country="UK"> <title>Dark Side of the Moon</title> <artist>Pink Floyd</artist> <price>10.90</price> </cd> <cd country="UK"> <title>Space Oddity</title> <artist>David Bowie</artist> <price>9.90</price> </cd> <cd country="USA"> <title>Aretha: Lady Soul</title> <artist>Aretha Franklin</artist> <price>9.90</price> </cd> </catalog>

An XML document

+Applying XSLT Stylesheets to XML Documents

There are three ways of applying an XSLT stylesheet to an XML document: Directly applying an XSLT processor to the XML document and

the XSLT stylesheet, Calling an XSLT processor from within a (Java) program, Adding to the XML document a link to the XSL stylesheet and

letting the browser do the transformation. This is what we will use

+Letting a Browser Perform the Transformation

<?xml version="1.0" encoding="ISO-8859-1"?>

<?xml-stylesheet type="text/xsl" href=“catalog.xsl"?>

<catalog> <cd country="UK"> <title>Dark Side of the Moon</title> <artist>Pink Floyd</artist> <price>10.90</price> </cd>

…</catalog> A link to the stylesheet

+The Root of the XSL Document (program) The Root of the XSL document should be one of the following

lines:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform>"

<xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform>"

• The namespace allows the XSL processor to distinguishbetween XSL tags and tags of the result document

+ How Does XSLT Work?

An XSL stylesheet is a collection of templates that are applied to source nodes (i.e., nodes of the given XML document).

Each template has a match attribute that specifies to which source nodes the template can be applied.

The current source node is processed by applying a template that matches this node.

Processing always starts at the root (/).

+Templates

A template has the form:

<xsl:template match="pattern">

... Template content ...

</xsl:template>

The content of a template consists of: XML elements and text (HTML, etc) that are copied to the result, XSL elements that are actually instructions.

The pattern syntax is a subset of Xpath.

<?xml version="1.0" encoding="ISO-8859-1"?><xsl:stylesheet version="1.0"xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/"> <html> <body> <h1>Hello World</h1> </body> </html></xsl:template>

</xsl:stylesheet>

Single Template XSL program

Applying a browser to catalog.xml(catalog.xml has a link to catalog.xsl)

<html>

<body>

<h1>Hello World</h1>

/<body>

/<html>

+Focus on Generating HTML

HTML

XML(content)

XSL(presentation)

XSLProcessor

+Transformation Language XSL is a transformation language it

transforms a document written in one language (XML) into a document of another language (e.g., HTML).

Transformation Engine(XSL Parser)

XSL

XML HTML

+Recall XML

Recall that an XML document is composed of ‘elements’.

For a BookCatalogue XML document we have the following elements: BookCatalogue (the ‘root’ element), Book, Title, Author, Date, ISBN, and Publisher.

+ XSL - all about (Template) “Rules”

Let the XSL processor know when it encounters the root element (e.g., BookCatalogue) do [action1].

Let the XSL processor know when it encounters the Book element do [action2].

Let the XSL processor know when it encounters the Title element do [action3].

And so forth…

+XSL - all about (Template) “Rules”

Each template rule has two parts: A pattern or matching part, that identifies the XML node in

the source document to which the action part is to be applied: Matching information is contained in an attribute.

An action or formatting, styling and processing part that details the transformation and styling of the resulting node

+XSL Document Structure

xsl:stylesheet

template rule for the document

(template rule for a child element)*

action on the document

action on the child element

+XSL Document Structure<?xml version=“1.0”?><xsl:stylesheet>

<xsl:template match=“/”> [action] </xsl:template>

<xsl:template match=“BookCatalogue”> [action] </xsl:template>

<xsl:template match=“Book”> [action] </xsl:template> ...</xsl:stylesheet>

+ Things to Note XSL documents are full-fledged XML documents:

As a consequence, if in [action] you want to, say, output an HTML paragraph break you must have both <p> and </p>: Even though in an HTML document the closing element (</p>)

is optional, Note: an XML all elements must have a closing element.

The root element of all XSL documents is xsl:stylesheet

To indicate that a template rule is to be applied to the XML document you use “/”

* Alternatively, <p/>

+ Template Rules

Template rules take the following general form:

<xsl:template match=“pattern”> [ action ]

</xsl:template>

+Template Rules (Example)

<xsl:template match=“Book”> <xsl:apply-templates/></xsl:template>

The XSL processor, as it parses through the XML documentand gets to a <Book> element use this template rule.”

<xsl:template match=“Book”>

“Go to each of my children and apply the template rules to them.”

<xsl:apply-templates/>

+Example - Create XSL for BookCatalogue.xml

<?xml version="1.0"?><!DOCTYPE BookCatalogue SYSTEM “BookCatalogue.dtd"><BookCatalogue> <Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>July, 1998</Date> <ISBN>94303-12021-43892</ISBN> <Publisher>McMillin Publishing</Publisher> </Book> <Book> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookCatalogue>

+First Example

This example will show how the XSL Processor parses an XML document and uses the template rules defined in the XSL document to do something for each thing that is found in the XML document.

+TerminologyIn BookCatalogue.xml we have (snippet):

<BookCatalogue> <Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>July, 1998</Date> <ISBN>94303-12021-43892</ISBN> <Publisher>McMillin Publishing</Publisher> </Book> ...</BookCatalogue>

• “Book is a child element of the BookCatalogue element. • Title, Author, Date, ISBN, and Publisher are children elements of the Book element.”

+Creating a Stylesheet - Step 1

Draw a tree diagram of your XML document.Documen

t/

DocumentType<!DOCTYPE BookCatalogue ...>

ElementBookCatalogue

ElementBook

ElementBook

ElementBook

ElementTitle

ElementAuthor

ElementDate

ElementISBN

ElementPublisher

... ...

TextMy Life ...

TextPaul McCartney

TextJuly, 1998

Text94303-

12021-43892

TextMcMillin Publishing

+Creating a Stylesheet - Step 2

Create a template rule for every type of node in your tree: Except for the DOCTYPE node:

The current specification does not allow you to have a template rule for the DOCTYPE node.

e.g., create one template rule for all the <Book> nodes, not one template rule for each of the nodes.

+ <?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="/"> <xsl:apply-templates/> </xsl:template> <xsl:template match="BookCatalogue"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Book"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Title"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Author"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Date"> <xsl:apply-templates/> </xsl:template> <xsl:template match="ISBN"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Publisher"> <xsl:apply-templates/> </xsl:template> <xsl:template match="text()"> <xsl:value-of select="."/> </xsl:template></xsl:stylesheet>

+Explanation

“The XSL processor returns the value of the thing that is selected here”

In this example the “thing” that is selected is a text node, so the “thing” that is returned is the value of the text node, i.e., the text.

<xsl:value-of select="."/>

+ Creating a Stylesheet - Step 3

For those nodes in the tree that we want to immediately return (i.e., not process any of its children): remove <xsl:apply-templates/> remove the template rules for the child nodes - these

template rules will never be used, so why have them?

For our example, we want the XSL processor to traverse the entire XML document tree so we do not do this step.

+<?xml version="1.0"?><xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl" > <xsl:template match="/"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <xsl:apply-templates/> </BODY> </HTML> </xsl:template> <xsl:template match="BookCatalogue"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Book"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Title"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Author"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Date"> <xsl:apply-templates/> </xsl:template> <xsl:template match="ISBN"> <xsl:apply-templates/> </xsl:template> <xsl:template match="Publisher"> <xsl:apply-templates/> </xsl:template> <xsl:template match="text()"> <xsl:value-of select="."/> </xsl:template></xsl:stylesheet>

added thesePut an

<HTML> wrapper around the content

+Creating a Stylesheet - Step 5 Tell the XSL Processor that when it encounters a

<Book> element to output: “I am at a Book element. Processing its children now.” Do this for each element.

Before running your XSL document through the XSL Processor, check it for well-formed-ness.

+<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl”> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <xsl:apply-templates/> </BODY> </HTML> </xsl:template> <xsl:template match="BookCatalogue"> I am at BookCatalogue. Processing its children now.<br/> <xsl:apply-templates/> </xsl:template> <xsl:template match="Book"> I am at Book. Processing its children now.<br/> <xsl:apply-templates/> </xsl:template> <xsl:template match="Title"> I am at Title. Here's the title:<br/> <xsl:apply-templates/><br/> </xsl:template> <xsl:template match="Author"> I am at Author. Here's the author's name:<br/> <xsl:apply-templates/><br/> </xsl:template> <xsl:template match="Date"> I am at Date. Here's the date:<br/> <xsl:apply-templates/><br/> </xsl:template> <xsl:template match="ISBN"> I am at ISBN. Here's the ISBN:<br/> <xsl:apply-templates/><br/> </xsl:template> <xsl:template match="Publisher"> I am at Publisher. Here's the publisher:<br/> <xsl:apply-templates/><br/> </xsl:template> <xsl:template match="text()"> <xsl:value-of select="."/> </xsl:template></xsl:stylesheet>

BookCatalogue1b.xsl

+Default Template Rules Every XSL document has two default template rules.

These rules are applied when the XSL Processor cannot find a template rule to use from what was written.

Here are the two default template rules:

<xsl:template match=“/ | *”><xsl:apply-templates/>

</xsl:template>

<xsl:template match=“text()”><xsl:value-of select=“.”/>

</xsl:template>

“Match on the document or any element. Return the result of applying the template rules to my children.”

“Match on a text node. Return the value of the text node, i.e., the text.”

+ Multiple Applicable Rules

Suppose that the XSL Processor is processing BookCatalogue and it gets to the <Book> element.

Why does it use <xsl:template match=“Book”>

and not the default template rule <xsl:template match=“/ | *”> after all, both apply!

Answer: given two rules that apply, the more specific rule wins: “*” is much more general than “Book”. “*” matches on any element. “Book” just matches on the Book element.

+Example 2 The XSL Processor, when it encounters a

book element output: ‘<p/>Here is a book:<br/>’ and then the data in its

children elements.

This is what we want XSLProcessor to send to BookCatalogue.html.

<HTML><HEAD><TITLE>Book Catalogue</TITLE></HEAD><BODY>Here is a book: all the data from the first bookHere is a book: all the data from the second bookHere is a book: all of the data from the third book</BODY></HTML>

+ BookCatalogue2.xsl

<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="BookCatalogue"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <xsl:apply-templates/> </BODY> </HTML> </xsl:template> <xsl:template match="Book"> <p/>Here is a book:<br/> <xsl:apply-templates/> </xsl:template></xsl:stylesheet>

+ Put the Data into an HTML Table<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="BookCatalogue”> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <TABLE BORDER="1" WIDTH="100%"> <xsl:apply-templates/> </TABLE> </BODY> </HTML> </xsl:template> <xsl:template match="Book"> <TR> <xsl:apply-templates/> </TR> </xsl:template> <xsl:template match="Title | Author | Date | ISBN | Publisher"> <TD> <xsl:apply-templates/> </TD> </xsl:template></xsl:stylesheet>

+ Single Rule Applied to Multiple Elements

Notice in the last example that a single rule is applied to multiple elements: <xsl:apply-templates select=“pattern”>

The xsl:apply-templates element (without an attribute) tells the XSL Processor to apply the template rules to all children

The xsl:apply-templates element can have an attribute that tells the XSL Processor to process only the child element that matches “pattern”: This apply-templates rule allows us to specify the order in

which the children are processed.

+Specify the order of the table contents

<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="BookCatalogue"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <TABLE BORDER="1" WIDTH="100%"> <xsl:apply-templates/> </TABLE> </BODY> </HTML> </xsl:template> <xsl:template match="Book"> <TR> <xsl:apply-templates select="Author"/> <xsl:apply-templates select="Title"/> <xsl:apply-templates select="Date"/> <xsl:apply-templates select="Publisher"/> <xsl:apply-templates select="ISBN"/> </TR> </xsl:template> <xsl:template match="Title | Author | Date | ISBN | Publisher"> <TD> <xsl:apply-templates/> </TD> </xsl:template></xsl:stylesheet>

Process the Author element first (in previous examplesthe Title element was processed first)

+<xsl:for-each select=“pattern”>

<xsl:for-each select=“Book”>[action]

</xsl:for-each>

This says that for every Book element, do [action]

+ For each Book do ...<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="BookCatalogue"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <TABLE BORDER="1" WIDTH="100%"> <xsl:for-each select="Book"> <TR> <xsl:apply-templates/> </TR> </xsl:for-each> </TABLE> </BODY> </HTML> </xsl:template> <xsl:template match="Title | Author | Date | ISBN | Publisher"> <TD> <xsl:apply-templates/> </TD> </xsl:template></xsl:stylesheet>

For each Book createa row and processthe Book’s children

+ Patterns So far we have seen very simple patterns - simply

match against an element name.

XSL provides a rich pattern matching capability.

<xsl:template match=“/”> “When you start processing the document do ...”

<xsl:template match=“Book”> “When you get to a Bookelement do ...”

<xsl:template match=“Title | Author”> “When you get to eithera Title element or an Authorelement do ...”

matchdocument

matchby name

matchseveralnames

+ Patterns

<xsl:template match=“Book/Title”> “When you get to a Titleelement that has a Bookelement as a parent do ...”

<xsl:template match=“BookCatalogue//Title”> “When you get to aTitle element that has aBookCatalogue as an ancestordo ...”

<xsl:template match=“Book/*”> “When you get to any elementthat is an immediate child of Book do ....”

<xsl:template match=“id(J.K)”> “When you get to an elementthat has an id “J.K.” do ...”

matchwithimmediateancestor

matchwithanancestor

wildcardmatch

matchby id

+Patterns (matching by attribute)<xsl:template match=“para”> “When you get to a para element

do ...”

<xsl:template match=“para[@type]”> “When you get to apara element that has anattribute called type do ...”

<xsl:template match=“para[@type =‘opening’]”> “When you get toa para element that has anattribute called type and its valueis ‘opening’ do ...”

<xsl:template match=“chapter[@num=‘ch1’]/para[@type=‘opening’]”>

“When you get to a para element that has an attribute called type whose value is ‘opening’ and the element has a parent called chapter and it has an attribute callednum that has a value ‘ch1’ do ...

+ Patterns (matching by position)

<xsl:template match=“Book[first-of-type()]”> “When you get to the first Book element do ...”

<xsl:template match=“Book[last-of-type()]”> “When you get to the last Book element do ...”

<xsl:template match=“Book[not(last-of-type())]”> “Use this rule for all but the last Book element”

Other position qualifiers:not(first-of-type())first-of-any() “The first child element of any type”not(first-of-any())last-of-any()not(last-of-any())

+Named Attribute Sets XSL allows you to create a set of attributes and

assign a name to it: What value is this? Reuse!

<xsl:attribute-set name=“title-attributes”> <xsl:attribute name=“size”>+1</xsl:attribute> <xsl:attribute name=“color”>blue</xsl:attribute> <xsl:attribute name=“face”>Palatino</xsl:attribute></xsl:attribute-set>

+<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:attribute-set name="title-attributes"> <xsl:attribute name=“size”>+1</xsl:attribute> <xsl:attribute name=“color>blue</xsl:attribute> <xsl:attribute name=“face>Palatino</xsl:attribute> </xsl:attribute-set> <xsl:template match="BookCatalogue”> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <TABLE BORDER="1" WIDTH="100%"> <xsl:apply-templates/> </TABLE> </BODY> </HTML> </xsl:template> <xsl:template match="Book"> <TR> <xsl:apply-templates/> </TR> </xsl:template> <xsl:template match="Author | Date | ISBN | Publisher"> <TD> <xsl:apply-templates/> </TD> </xsl:template> <xsl:template match="Title"> <TD> <FONT> <xsl:use attribute-set="title-attributes"/> <xsl:apply-templates/> </FONT> </TD> </xsl:template></xsl:stylesheet>

Use the named attribute set

Define the named attribute set

+Numbering XSL has the capability to number your elements:

<xsl:number/>.<xsl:apply-templates select="Title"/>

This will print out a number followed by a periodfollowed by the results of processing the Title element. The number starts at one and increments each time this template rule is instantiated.

+Creating a Numbered Title List<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl”> <xsl:template match="BookCatalogue"> <HTML> <HEAD> <TITLE>Book Catalogue</TITLE> </HEAD> <BODY> <TABLE BORDER="1" WIDTH="100%"> <xsl:apply-templates/> </TABLE> </BODY> </HTML> </xsl:template> <xsl:template match="Book"> <xsl:number/>.<xsl:apply-templates select="Title"/><br/> </xsl:template> <xsl:template match="Title"> <xsl:apply-templates/> </xsl:template></xsl:stylesheet>

Here is wherewe use the number capability

+ Sorting Sorting is achieved by adding xsl:sort elements

as children of xsl:apply-templates or xsl:for-each.

The first xsl:sort child specifies the primary sort key, the second xsl:sort specifies the secondary sort key, and so on.

<?xml version="1.0"?><xsl:stylesheet xmlns:xsl=“http://www.w3.org/TR/WD-xsl” > <xsl:template match="BookCatalogue"> <xsl:apply-templates select=“Book”> <xsl:sort select=“Title” order="ascending"/> </xsl:apply-templates> </xsl:template> <xsl:template match="Book"> <xsl:number/>.<xsl:apply-templates select="Title"/><br/> </xsl:template> <xsl:template match="Title"> <xsl:apply-templates/> </xsl:template></xsl:stylesheet>

+if test

<xsl:template match="Book">  <xsl:if test=".[first-of-type()]"> <B><FONT COLOR="#0000FF">TO</FONT></B> <TR><TD><FONT COLOR="#0000FF">Title</FONT></TD></TR> </xsl:if> <TR><TD><xsl:apply-templates /></TD></TR></xsl:template>

<xsl:template match="Date">  <xsl:if test=".[not(month)]">-</xsl:if> <xsl:apply-templates /></xsl:template>

+A Common Mistake

<xsl:template match="Book">  <a href=“#<xsl:value-of select=‘(@id)’/>”></xsl:template>

<xsl:template match="Book">  <a href=“#{@id}”></xsl:template>

Wrong

Correct

Attributes valuescannot contain“<” or “>”

• Scenario: suppose that the element Book has an id attribute.

• We would like to create a hyperlink using the value of the id attribute as the value of the hyperlink’s href.

+Summary

XSLT is a high-level transformation language.

Create core output once in XML format - using Servlets, JSP, etc.

Use XSLT to transform the core output as needed.