XSLT

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∗ XSL: EXtensible Stylesheet Language. ∗ Defined by the WWW Consortium (W3C) ∗ CSS – Stylesheets for HTML ∗ XSL – Stylesheets for XML ∗ XSL consists of three parts: ∗ XSLT - a language for transforming XML documents ∗ XPath - a language for navigating in XML documents ∗ XSL-FO - a language for formatting XML documents

Introduction

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∗ A common way to describe the transformation process is to say that XSLT transforms an XML source-tree into an XML result-tree

∗ XSLT is used to transform an XML document into another XML document, or another type of document that is recognized by a browser, like HTML and XHTML

∗ With XSLT you can add/remove elements and attributes to or from the output file.

∗ You can also rearrange and sort elements, perform tests and make decisions about which elements to hide and display

XSLT

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∗ Write an XML ∗ Write an XSLT ∗ Declaring XSLT: <xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

∗ Link the XSLT to XML Document: <?xml-stylesheet type="text/xsl" href=“XSLName"?>

XSLT - Transformation

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∗ xsl:template Element ∗ Is used to build templates ∗ The match attribute is used to associate a template with an XML

element

∗ xsl:value-of element to select values from the XML elements. ∗ xsl:for-each element can be used to select every XML element of

a specified node-set ∗ Filtering the output:

∗ Filter the output from the XML file by adding a criterion to the select attribute

∗ Eg: <xsl:for-each select="catalog/cd[artist=‘SDTech']“/>

XSLT - Basics

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∗ The <xsl:if> element is used to put a conditional test against the content of the XML file ∗ Eg: <xsl:if test="price &gt; 10"> … </xsl:if>

∗ The <xsl:choose> element is used in conjunction with <xsl:when> and <xsl:otherwise> to express multiple conditional tests. ∗ Eg: <xsl:choose>

<xsl:when test="expression"> ... some output ... </xsl:when> <xsl:otherwise> ... some output .... </xsl:otherwise> </xsl:choose>

XSLT - Basics

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∗ Templates ∗ Are rules to apply to the data

∗ Similar to Procedures / Functions

∗ Two ways to call the templates

∗ <xsl:call-template> ∗ <xsl:apply-templates>

XSLT - Basics

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XPath

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∗ XPath is a W3C recommendation ∗ XPath contains a library of standard functions ∗ XPath uses path expressions to select nodes or node-sets in an

XML document. ∗ Helps you navigate through the XML document. ∗ Simple language consisting of path expressions. ∗ XPath uses expressions to select nodes or node-sets in an XML

document ∗ Each vendor has already defined a lot of XPath functions

XPath

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∗ Nodes: ∗ Element ∗ Attribute Text ∗ Namespace ∗ Processing-instruction ∗ Comment ∗ Document nodes

∗ Relationship of Nodes: ∗ Parent ∗ Children ∗ Siblings ∗ Ancestors ∗ Descendants

XPath Terminology

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Expression Description

Nodename Select all nodes with the name “nodename”

/ Selects from root nodes

// Selects nodes in the document from the current node that match the selection no matter where they are

. Selects the current node

.. Selects the parent of current node

@ Selects attributes

XPath Expressions

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Expression Description

* Matches any element node

@* Matches any attribute node

| Selects two nodes with AND

. Selects the current node

.. Selects the parent of current node

@ Selects attributes

XPath Wildcards

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AxisName Result

ancestor Selects all ancestors (parent, grandparent, etc.) of the current node

ancestor-or-self Selects all ancestors (parent, grandparent, etc.) of the current node and the current node itself

attribute Selects all attributes of the current node

child Selects all children of the current node

descendant Selects all descendants (children, grandchildren, etc.) of the current node

descendant-or-self Selects all descendants (children, grandchildren, etc.) of the current node and the current node itself

following Selects everything in the document after the closing tag of the current node

following-sibling Selects all siblings after the current node

namespace Selects all namespace nodes of the current node

parent Selects the parent of the current node

preceding Selects all nodes that appear before the current node in the document, except ancestors, attribute nodes and namespace nodes

preceding-sibling Selects all siblings before the current node

self Selects the current node

XPath Axes An axis defines a node-set relative to the current node.

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AxisName Result

Round(number) Rounds the number argument to nearest integer

Substring(string, start, len)

Returns sub-string from start position to specified length

String-length Returns length of the string

Day-from-datetime Returns the day of the date.

Max() Returns maximum value from set of numbers

XPath Functions

Lots of pre-defined functions. Few of them are below

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XQuery

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XQuery

∗ XQuery is a W3C recommendation ∗ XQuery : XML what SQL : database tables ∗ XQuery is designed to query XML data. ∗ XQuery is built on XPath expressions ∗ XQuery is supported by all major databases.

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XQuery – Basics

∗ Uses functions to extract data from XML documents. ∗ Uses path expressions to navigate through elements in an XML

document. ∗ Uses predicates to limit the extracted data from XML

documents. ∗ Can also transform the XML document into other format. ∗ XPath terminology and relationship applies to XQuery also.

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XQuery – Basics

∗ FLWOR is an acronym for "For, Let, Where, Order by, Return". ∗ The for clause selects all book elements under a node

element into a variable. ∗ The where clause selects only elements with a filter. ∗ The order by clause defines the sort-order. Will be sort by the

specified element. ∗ The return clause specifies what should be returned.

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XQuery – Syntax

∗ XQuery is case-sensitive ∗ XQuery elements, attributes, and variables must be valid XML

names ∗ An XQuery string value can be in single or double quotes ∗ An XQuery variable is defined with a $ followed by a name ∗ XQuery comments are delimited by (: and :), e.g. (: XQuery

Comment :)

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