Transforming XML XMLNamespaces, XSLT. XML Namespaces Sometimes it is necessary to mix XML elements –Different types of content –Use of markup to convey.

Transforming XML

XMLNamespaces, XSLT

XML Namespaces

• Sometimes it is necessary to mix XML elements– Different types of content

– Use of markup to convey meta-information

• Some documents combine markup from different XML languages

• But:– Elements and attributes from different XML languages

may share the same name

– Need to group elements for processing

XML Namespaces

• XML Namespaces is the xml standard for distinguishing xml elements

• Namespaces are represented by attributes

• Elements from the same namespace can be recognised by software as a group

• Unique namespaces are defined by a URI

URL, URN, URI

• URL: a Uniform Resource Locator• specifies the mechanism by which a resource is accessed

• e.g. http://www.comp.rgu.ac.uk/home.html

• URN: a Uniform Resource Name• a unique sequence of characters naming an internet

resource e.g. urn:Turquoise.Inflatable.Walrus• the name has persistence even if the resource becomes

unavailable

• URI– uniform resource identifier

• a URL or a URN (see RFC 2396 at www.ietf.org)

the namespace prefix

• short string representing the namespace URI• distinguishes element and attribute names• defined using an xmlns:prefix attribute

– <xs:schema xmlns:xs= “URI”>

• a prefixed element name is called a qualified name, or QName, or a raw name

• QName syntaxprefix:local_part

example

• SVG and MathML both contain a set element

• Both SVG and MathML can be embedded in XHTML documents

• prefixes svg and mathml are used to distinguish the set elements

<svg:set> distinct from <mathml:set>

example 2:xml with multiple namespaces

<?xml version=“1.0”>

<html xmlns=“http://www.w3.org/1999/xhtml”

xmlns:xlink=“http://www.w3.org/1999/xlink”>

<head><title>Three Namespaces</title></head>

<body>

<h1 align=“center”>Ellipse and Rectangle</h1>



xlink prefix associated to the xlink namespace everywhere

within the root element

xhtml namespace associated to root html element and all

descendants (no prefix needed)

all (blue) elements are in the xhtml namespace

xml declaration

xml with multiple namespaces<svg xmlns=“http://www.w3.org/2000/svg”

width = “12cm” height = “10cm”>

<ellipse rx=“110” ry=“130”>

<rect

x=“4cm” y=“1cm”

width=“3cm” height=“6cm”>

</svg>



svg namespace associated to root svg element and all

descendants (no prefix needed)

all (red) elements are in the svg namespace

xml with multiple namespaces

<p xlink:type=“simple”

xlink:href=“ellipses.html”>

More about ellipses </p>

<p xlink:type=“simple”

xlink:href=“rectangles.html”>

More about rectangles </p>

<hr />

<p>Last Modified 7th October 2003</p>

</body></html>

all (blue) elements are in the xhtml namespace

prefixed QNamed attributes (green) are in the xlink

namespace

more on namespaces

• namespace can be defined in the element where it is used or in the root

• namespaces are identified by the URI, not the prefix used in a particular document

• the parser doesn’t look up the URI – it is only there as a unique identifier!

more on namespaces

• namespaces are completely independent of DTDs

• QNames, if used, must be defined as elements in the DTD for them to be valid– parameter entities are used to get round this

• ingenious but awkward kludge

• not required for this module!

• namespaces important in XSLT documents

Introduction to XSLT

what is XSL?• XML & client/server model

– XML sits on server but does not do anything– XSL provides client views of data

• XSL: eXtensible Stylesheet Language– two separate namespaces

• XSL-FO (Formatting Objects)

• XSLT (Transformations)

– X-Path used to navigate XML

• defines rules for transforming a source XML document into a target document

what is XSLT?

• Transforms source tree to results tree by:– Selecting elements– Selecting attributes– Rearranging elements– Sorting elements– Applying conditional tests

• XML/XSTL Similar to HTML/CSS

the XSLT transformation process

XSLTdocument

XSLTprocessor

XMLsource

outputdocument

set oftemplate rules

match elements and replace using template rules

a simple XSLT example

the source

<?xml version = “1.0”?>

<people>

<person born=“1912” died=“1954”>

<name><first_name>Alan</first-name>

<last_name>Turing</last_name>

</name>

<profession>computer scientist</profession>

<profession>mathematician</profession>

<profession>cryptographer</profession>

</person>





<person born=“1918” died=“1988”>

<name><first_name>Richard</first-name>

<middle_initial>P</middle_initial>

<last_name>Feynman</last_name>

</name>

<profession>physicist</profession>

<hobby>playing the bongoes</hobby>

</person>

</people>


the transforming stylesheet


<xsl:stylesheet version = “1.0”

xmlns:xsl=“http://www.w3.org/1999/XSL/Transform”></xsl:stylesheet>

• xsl prefix identifies xsl QNames as belonging in the XSLT namespace associated to the given URI

• the empty stylesheet

• contains no template rules

• will apply default rules (see later)


the output of the transform

Alan

Turing

computer scientist

mathematician

cryptographer

Richard

P

Feynman

physicist

playing the bongoes

default behaviour strips out the mark up and returns a text document that reproduces the content of the XML (including whitespace like tabs and carriage returns)

to modify the default behaviour, we add template rules that describe how to transform elements of the source document

template rules• a template rule is defined by an

<xsl:template> element

• the match attribute contains a pattern identifying the input to which the rule is applied

• the content of the element is a template for the output from the matched pattern

<xsl:template match=“pattern”>

template

</xsl:template>

example 2



xmlns:xsl=“http://www.w3.org/1999/XSL/Transform”>

<xsl:template match = “person”>

A Person

</xsl:template>

</xsl:stylesheet>


<people> <person born=“1912” died=“1954”> <name><first_name>Alan</first-name>

<last_name>Turing</last_name> </name> <profession>computer scientist</profession> <profession>mathematician</profession> <profession>cryptographer</profession> </person> <person born=“1918” died=“1988”> <name><first_name>Richard</first-name>

<middle_initial>P</middle_initial><last_name>Feynman</last_name>

</name> <profession>physicist</profession> <hobby>playing the bongoes</hobby> </person></people>

example 2 output

A Person

A Person

Each person element in the original document has been replaced entirely by the template.

The whitespace outside each person element has been preserved

example 3





<p>A Person</p>

</xsl:template>

</xsl:stylesheet>

elements used in a template must preserve well-formedness of the document

example 3 output

<p>A Person</p>

<p>A Person</p>

The <p> and </p> tags have also been copied over from the template

The whitespace outside each person element has been preserved

xsl:value-of

• xsl element which extracts the string value of an element in the source XML– the string value is the text content after:

• all tags have been removed

• entity and character references have been resolved

• select attribute specifies the element whose value is taken

example 4





<p>

<xsl:value-of select = “name” />

</p>

</xsl:template>

</xsl:stylesheet>


<people> <person born=“1912” died=“1954”> <name><first_name>Alan</first-name>

<last_name>Turing</last_name> </name> <profession>computer scientist</profession> <profession>mathematician</profession> <profession>cryptographer</profession> </person> <person born=“1918” died=“1988”> <name><first_name>Richard</first-name>

<middle_initial>P</middle_initial><last_name>Feynman</last_name>

</name> <profession>physicist</profession> <hobby>playing the bongoes</hobby> </person></people>

example 4 output<p>

Alan

Turing

</p>

<p>

Richard

P

Feynman

</p>

the full text content of the <name> element after the <first_name>, <middle_name>, and <last_name> tags have been stripped out

The whitespace inside each name element has been preserved along with the rest of the text content

example 4a<?xml version = “1.0”?>




<p>

<xsl:value-of select = “@born” />-

<xsl:value-of select = “name” />

</p>

</xsl:template>

</xsl:stylesheet>

example 4a output<p>

1912 -

Alan

Turing

</p>

<p>

1918 -

Richard

P

Feynman

</p>

the value of attribute <born> associated with element <person> is added to the output

<xsl:apply-templates>

• xsl element that can affect the default order of processing– which elements should be processed next– process elements in the middle of processing

another element– prevent particular elements from being

processed

• select attribute contains a pattern identifying elements to be processed at that point

example 5<?xml version = “1.0”?>




<xsl:apply-templates select = “name” />

</xsl:template>

<xsl:template match = “name”>

<xsl:value-of select = “last_name” />,

<xsl:value-of select = “first_name” />

</xsl:template>

</xsl:stylesheet>

example 5 outputTuring,

Alan

Feynman,

Richard

The order of processing has been changed.

The output for each <name> consists of the full text content of the <last_name>, followed by a comma and a new line, followed by the full text content of the <first_name>.

The <profession> and <hobby> elements are never processed because <apply-templates> bypasses them

XSLT processor• a software component that

• reads a XML source document and a stylesheet

• applies the transformation rules

• outputs the transformed document

• standalone• SAXON

• Apache Xalan (used in NetBeans)

• built into a browser or application server• MSXML (built in to IE6)

• Apache Cocoon (built in to Apache server)

Stylesheet Example – XML (catalog.xml)

<?xml version="1.0" ?><catalog> <cd> <title>Empire Burlesque</title> <artist>Bob Dylan</artist> <country>USA</country> <company>Columbia</company> <price>10.90</price> <year>1985</year> </cd> <cd> <title>ESSSSSSSSS</title> <artist>Bruce</artist> <country>Uk</country> <company>Cola</company> <price>12.90</price> <year>1988</year> </cd></catalog>

Stylesheet Example –XSL (cdcatalog.xsl)<?xml version="1.0" ?><xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/"> <html> <body> <h2>My CD Collection</h2>

<xsl:apply-templates/> </body></html>

</xsl:template> <xsl:template match="cd"> <p> Title: <xsl:value-of select="title"/> <br /> Artist: <xsl:value-of select="artist"/> </p> </xsl:template></xsl:stylesheet>

Stylesheet Example –Linking XML to Stylesheet<?xml version="1.0" ?>

<?xml-stylesheet type="text/xsl" href="cdcatalog.xsl"?><catalog> <cd> <title>Empire Burlesque</title> <artist>Bob Dylan</artist> <country>USA</country> <company>Columbia</company> <price>10.90</price> <year>1985</year> </cd> <cd> <title>ESSSSSSSSS</title> <artist>Bruce</artist> <country>Uk</country> <company>Cola</company> <price>12.90</price> <year>1988</year> </cd></catalog>

My CD Collection

Title: Empire BurlesqueArtist: Bob Dylan

Title: ESSSSSSSSSArtist: Bruce

Stylesheet Example – HTML Output

Summary• Namespaces

– allow elements from different XML languages to be included in same XML

– xmlns:xlink=http://www.w3.org/1999/xlink

• XSLT– <xsl:stylesheet version = “1.0” xmlns:xsl=“URI”/>– Create templates with <xsl:template match=“/”>– Select content with

• <xsl:value-of select =“name” />• <xsl:value-of select =“@id” />

– Control content with• <xsl:apply-templates/>• <xsl:apply-templates select = “name” />

Useful websites• Standards:

– www.w3.org/Style/XSL/- administrates xsl std• www.w3.org/TR/xslt

• www.w3.org/TR/xpath

• www.w3.org/TR/xsl/

• Tutorials/Forums– www.w3schools.com/xsl– www.learn-xslt-tutorial.com/– www.xml.com– www.tizag.com/xmlTutorial/xslttutorial.php

Transforming XML XMLNamespaces, XSLT. XML Namespaces Sometimes it is necessary to mix XML elements –Different types of content –Use of markup to convey.

Documents

xslt slide

uri slide

person slide

source slide

xml namespaces xml namespaces

svg namespace slide

transform slide

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