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XSL Transformation

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XSL

XSL (eXtensible Stylesheet Language) is a language for expressing style sheets.

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What is a Stylesheet?

A stylesheet is a file which contains a set of rules for converting an XML document into another document, which can be XML, HTML, plain text …

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Style Sheet Specifications

XSL - Extensible Style Language Combines features of DSSSL and CSS using XML syntax

DSSSL - Document Style and Semantics Specification Language An international SGML standard for Scheme-like

languages for style sheets and document conversion

CSS - Cascading Style Sheet Specification Simple syntax for assigning styles to elements (in some

HTML browsers)

XSLT is an XML Document!

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XSL

It consists of three parts: XSL Transformations (XSLT): a language for

transforming XML documents An XML vocabulary for specifying formatting

semantics (XSL Formatting Objects) An expression language used by XSLT to

access or refer to parts of an XML document (XPATH)

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XSL-FO

Used to describe XML documents for display

W3C recommendation 15 October 2001 A language for completely describing a

styled document (content organization, styling, layouts and layout-selection rules)

Everything needed to format and paginate a document!

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XPath

Used in conjunction with XSLT Became a W3C recommendation 16

Nov 1999 Provides a language for pointing to

different parts of an XML document specifies location path from specific

context nodes (i.e. starting points)

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XPath Expressions

Addresses a specific part or parts of XML documents which then allows XSLT to transform them

Provides expressions for manipulation of strings, Booleans, numbers so that the XSL elements can act upon them

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XSLT

XSLT is the most important part of the XSL Standard.

It is the part of XSL that is used to transform an XML document into another XML document, or another type of document (text, java code, …)

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XSLT

XSLT can be used to manipulate an XML document

Can transform/extract information as a programming language can

Can be used like a database language to extract information

Uses XML syntax

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XSLT is rule-based

XSLT is based on template rules which specify how XML documents should be processed.

Template rules can be based in any order because XSLT is a declarative language.

The stylesheet declares what output should be produced when a pattern in the XML document is matched.

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Example

A stylesheet could declare that when the XSLT transformation engine finds a 'NAME' element it should add markup by calling the 'NAME' template.

The template syntax is:

<xsl:template match="NAME">    ...

</xsl:template>

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XSLT Capabilities

Add prefix or suffix text to content Remove, create, re-order and sort

elements Re-use elements elsewhere in the

document Transform data between XML formats Uses a recursive mechanism to go

through document

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XSLT consists of two parts

A source document original xml document

A result tree newly-created xml, html or a plain text

document A common way to describe the

transformation process is to say that XSL uses XSLT to transform an XML source tree into an XML result tree.

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Trees & Nodes

With XSLT one does not think in terms of documents, but in terms of trees & nodes

A tree represents the data in a document as a set of nodes

Nodes are elements, attributes, comments, etc in a hierarchy

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Structure of Style Sheet

style sheet Style sheet is made up of templates Templates have other XSL elements/XPath expressions Style sheet is usually given extension *.xsl Must be well-formed XML

XSLT has a number of pre-defined elements to perform certain transformations <xsl:stylesheet> <xsl:template> <xsl:value-of> <xsl:if> <xsl:choose> …

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A Sample XML file

<?xml version="1.0"?><!-- File Name: XslDemo01.xml --><?xml-stylesheet type="text/xsl" href="XslDemo01.xsl"?><BOOKS><BOOK> <TITLE>Moby-Dick</TITLE> <AUTHOR> <FIRSTNAME>Herman</FIRSTNAME> <LASTNAME>Melville</LASTNAME> </AUTHOR> <BINDING>hardcover</BINDING> <PAGES>724</PAGES> <PRICE>$9.95</PRICE></BOOK>

…

</BOOKS>

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A simple transformation of an XML file

Book Description

Author: Herman MelvilleTitle: Moby-DickPrice: $9.95Binding type: hardcoverNumber of pages: 724

Author: John DoeTitle: TalesPrice: $19.95Binding type: softcoverNumber of pages: 450

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<?xml version ="1.0"?><xsl:stylesheet version ="1.0"

xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:template match="/"><HTML><HEAD><TITLE>XSLT Test</TITLE></HEAD><H2>Book Description</H2><xsl:for-each select=“/BOOKS/BOOK”>

<Span Style="font-style:italic">Author: </Span> <xsl:value-of select=“./AUTHOR"/><br/>

<span style="font-style:italic">Title: </span> <xsl:value-of select=“./TITLE"/><br/>

<span style="font-style:italic">Price: </span> <xsl:value-of select=“./PRICE"/><br/>

<span style="font-style:italic">Binding: </span> <xsl:value-of select=“./BINDING"/><br/>

<span style="font-style:italic">Number of Pages: </span> <xsl:value-of select=“./PAGES"/><br/></xsl:for-each></HTML></xsl:template></xsl:stylesheet>

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XSL Processor

An XSL processor can transform an input XML document to a XML or any other output document based on rules in a second XML document (i.e. a XSLT file)

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Template Matching

XPath is used by XSLT in the match attribute of a template e.g. <template match=“sentence”> matches any sentence element.

The stylesheet processor goes through the XML document one element at a time, finds the first template which that element matches, and carries out the instructions in that template.

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Template Matching (cont)

If the element does not match any template in the stylesheet, then the default behaviour is for the processing to pass through to the children of this element without carrying out any instructions.

When the processing reaches an element which has only text children, the result of processing these children is to print out the text.

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Some examples of patterns

* matches any element / matches the top-level element sentence/word matches any word

element with a sentence parent word[@pos=‘noun’] matches any

noun element whose pos attribute has the value noun

Many other possibilities …

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Some XSLT Syntax and Elements

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To begin

Start by declaring that this is an xml document <?xml version ="1.0"?>

Next: declare the processing instruction & the namespace

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/

Transform" version="1.0">

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XSLT Namespace

Every XSL file needs to specify the XSL namespace so that the parser knows which version of XSLT to use.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/

Transform" version="1.0"> The namespace prefix xsl: is used in the rest of

the XSL file to identify XSL processing statements.

If a statement isn't prefixed with xsl:, then it's simply copied to the output without being processed.

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XSL Elements

<xsl:template [match = “/”]> Before processing can begin, the part of the XML

document with the information to be copied to the output must be selected with an XPath expression.

The selected section of the document is called a node and is normally selected with the match operator.

If the entire document is to be selected, match the root node using match="/".

Another approach is to match the document element (the element that includes the entire document).

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XSL Elements ..

<xsl:apply-templates> The <xsl:apply-templates> element

applies a template rule to the current element or to the current element's child nodes.

If we add a select attribute to the <xsl:apply-templates> element it will process only the child element that matches the value of the attribute.

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XSL Elements ..

<xsl:for-each> allows for processing on a number of

nodes in the source tree, one at a time Attributes

• “select” denotes the path to the nodes Example

<xsl:for-each select=“/BOOKS/BOOK” >.. // other xsl elements</xsl:for-each>

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<xsl:value-of> When the xsl:for-each expression has

selected a ‘BOOKS' element, the xsl:value-of expression extracts and copies to the output file the value stored in the selected element.

syntax: <xsl:value-of select= Examples

<xsl:value-of select="."><xsl:value-of select="customer/@id"><xsl:value-of select="author"/>

XSL Elements ..

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XSL Elements ..

<xsl:if> Allows for conditional processing.

• Attribute: test Example

<xsl:if test=“title[@type=‘main]”><b><xsl:apply-templates/></b></xsl:if>

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XSL Elements ..

<xsl:sort> XSLT can be used to sort elements by

alphabetical or numerical order, according to attribute values, text contents, in ascending or descending order, and more … <xsl:sort

    select = string-expression     data-type = { "text" | "number" | Qname }    order = { "ascending" | "descending" }    case-order = { "upper-first" | "lower-first" }    lang = { language-code }/> 

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More XSL Elements ..

Some of the xsl elements not covered <xsl:choose> <xsl:when> <xsl:attribute> <xsl:element> <xsl:comment> <xsl:text> <xsl:variable>

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XSLT

Thank you!