XML Part 2

XML Part 2

Josh SteeleCS 6704, Spring 2002

XML Part 2

• XSL/XSLT– Structure Revisited – Definition– Example– Components

• XML’s Linking Languages• XML’s Uses

Structure Revisited

Information Structure

Display

XML File

XSL File

XML Schema (.xsd) File

XSL

• Stands for Extensible Stylesheet Language• Parts:

– XSLT – handles transformations– XPath – used to access or refer to parts of an XML

document– Formatting objects – XML Vocabulary for specifying

formatting semantics• Compatible with CSS2 (uses different syntax

though)

XSLT

• Transforms one set of XML tags to another set of XML tags

• Benefits of this?

Example - XML<?xml version=“1.0”?><?xml-stylesheet type=“text/xsl” href=“myxsl.xsl”?><Recipe xmlns:rec=“http://www.mysite.org/Recipe”xmlns:xsi=http://www.w3.org/2001/XMLSchema-instancexsi:schemaLocation=“myxsd.xsd” ><rec:Recipe cook = “XML Gourmet”>

<rec:Title>Bean Burrito</Title><rec:Category name = “tex-mex” /><rec:Ingredients>

<rec:Item>1 can refried beans</Item><rec:Item>1 cup longhorn colby cheese, shredded</Item>……

</rec:Ingredients><rec:Cooking Instructions>

Empty can of refried beans</rec:Cooking Instructions>

……</rec:Recipe>

XML Schema<?xml version="1.0" encoding="utf-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name=“recipe"> <xs:complexType> <xs:sequence> <xs:element name=“Title" type="xs:string"/> <xs:element name=“Category" type="xs:string"/> <xs:element name=“Ingredients" type="xs:string">

<xs:complexType> <xs:element name=“Item" minOccurs=“1" maxOccurs="unbounded“ type=“xs:string”/> </xs:complexType> </xs:element> <xs:element name=“CookingInstructions" type="xs:string"/> </xs:sequence></xs:complexType></xs:element>

</xs:schema>

Example - XSLT<xsl:stylesheet version = “1.0” xmlns:xsl=“http://www.w3.org/1999/XSL/Transform” xmlns=“http://www.w3.org/TR/xhtml1/strict”>

<xsl: outputmethod=“xml”encoding=“iso-8859-1” />

<xsl: template match = “Recipe”><html>

<head><title>

<xsl value-of select=“Recipe/Title” /></title>

</head><body>

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

</html></xsl: template>

Example - XSLT (cont)<xsl:template match=“Recipe/Title”>

<h1><xsl:apply-templates />

</h1></xsl:template>

<xsl:template match=“Recipe/Ingredients”><h2>Ingredients</h2><ul>

<xsl:for-each select=“Item”><li>

<xsl:apply-templates /></li>

</xsl:for-each></ul>

</xsl:template>

<xsl:template match = “Recipe/CookingInstructions”><h2> Cooking Instructions </h2><p>

<xsl:apply-templates /></p>

</xsl:template>………

Components

• Template– Defines what should be changed, and how

• Pattern– Uses “match=“ attribute in template tag to point to a

specific element (uses XPath, more later)• Results

– Includes the HTML tags specified– <xsl: apply templates /> - applies template to the text

encapsulated by the tag (i.e. <CookingInstructions>)

Components (cont)

• Text– Literal text can be captured with the

<xsl:value-of> tag• Repetition

– Handled by use of the <xsl:for-each> tag

XML’s Linking Languages

• XLink– Alternative to XHTML for linking (the <a> tag) – <xmlns:xlink=http://www.w3.org/1999/xlink/namespace>

– <xlink:simple> – works just like <a> (with some more features)

– <xlink:extended>, <xlink:locator>, <xlink:arc > - provides a whole new set of linking policies

http://www.w3.org/1999/xlink/namespace

XLink: Simple

• Attributes:– href - resource you are linking to– role - string used to describe element’s role– title – optional title of link– show - opens the new resource in its own

window (new), embeds it in the current window (embed), or replaces the current window with the new one (replace)

– actuate – onRequest (click a link) or auto (like loading in <img>)

XLink:Extended

• Attributes:– Role, title – as in <xlink:simple>– showdefault – default value of show for all

locator elements– actuatedefault – default value of actuate for all

child elements– Needs helpers: <xlink:locator>, <xlink:arc>

XLink:LocatorThese <xlink:extended

role=“weapon list”title=“Description of Weapons”showdefault=“new”show actuate=“onRequest”>weapons

<xlink:locator title=“Longbow” href=“longbow.htm”/>

<xlink:locator title=“Crossbow” href=“crossbow.htm”/>

<xlink:extended> revolutionized medieval warefare……

XLink:arc

• Locators can be specified out-of-line– <xlink:locator href=“weaponlinkset.xml”/>– Allows different show and actuate parameters for

each locator• xlink:arc specifies those values in above file:

xlink:arcfrom=“sourcedoc”to=“longbowpic”show=“embed”actuate=“auto”/>

XPath

• Purposes:– To find and describe a section in the XML file

(used in XSLT)– To be able to point to a certain part of the

document (used in XPointers)• In essence makes a parse tree describing

the relationships between tags in the file

XPointers

• Allows one to point into a document (similar to anchors in HTML), but without any special notation (like id=“mytaghere”)

• Also allows selection of a section of the file (i.e. if you want section 25, it only downloads section 25, not the whole file)

XPointers (cont)

• 3 ways to reference:– #anchor (like in HTML)– #/1/3/4 (3rd tag under root, 4th tag under that)– #xptr (XPath expression)

• If you aren’t sure if there is an ID, you can concatenate different reference methods together

• Range: XPtr(id(“c2”) to id(“c3”))

XML Uses

• MathML – allows math expressions in web pages (www.w3.org/Math)

• XML-Data – provides mechanism to reference binary data within XML docs

• XHTML – a merging of XML and HTML• WIDL – Web Interface Definition

Language – allowed direct access to Web data from e-commerce or business apps

• And many more!

http://www.w3.org/Math

References

• XML for Dummies, 2nd edition (Ed Tittel, Frank Boumphrey)

• http://www.w3.org/TR/WD-xptr - XPointer• http://www.w3.org/TR/xslt - XSLT• http://www.w3.org/Style/XSL/ - XSL• http://www.w3.org/XML/ - XML

Documents

XML Part 2