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XSLT II

Robin Burke

ECT 360

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Outline

Conditionals Numbering Functions and operators Variables and parameters Named and recursive templates

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Conditional nodes

XSLT supports two kinds of conditional elements:

<xsl:if> <xsl:choose>

If is only if-then (no else)Choose is more general

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Example

if choose

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Comparison operators

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Predicates

XPath expressionstest for a conditionresult = set of nodes that fulfill that

condition

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Example

from last week

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Numbering

Number nodes using:<xsl:number>position()

Using position():Nodes are numbered by position in

result documentCan be used in conditional statements

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Number element

Nodes are numbered according to position in source document

Attributes:value=expression: any XPath expression

that evaluates to a number (i.e. position())count=pattern: specifies which nodes to

countlevel=type: tree level for nodes to count;

can be any, single, or multiple

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USING <XSL:NUMBER>

Attributes:from=pattern: pattern indicates where

numbering should restartformat=pattern: pattern indicates

number formatgrouping-size, grouping-separator:

indicate how digits are grouped and separator character

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Example

numbering

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XPath numerical functions

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XPath string functions

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XPath operators

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Example

Calculating the average

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Number format

XPath function format-number Syntax: format-number(value, format) Example: format-number(56823.847,

'#,##0.00') displays 56,823.85

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Number format syntax

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Decimal format

XSL element for defining number formats

Named decimal format passed as argument to format-number

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Variables

Not variable! User-defined name that stores a particular

value or object Types:

numbertext stringnode setbooleanresult tree fragment

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Using variables

Syntax: <xsl:variable name=“name” select=“value”/>

Example: <xsl:variable name=”Months” select=”12” />

Names are case-sensitive Value only set once upon declaration Enclose text strings in single-quotes

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Using variables

Value can be XPath expression Value can be XML fragment

Syntax:

<xsl:variable name=”Logo”>

<img src=”logo.gif” width=”300” height=”100” />

</xsl:variable>

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Variable reference

Syntax: $variable-name Example: $Months Referencing tree fragments:

Do not use $variable-nameUse <xsl:copy-of> to reference value

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COPYING

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Global variables

Can be referenced from anywhere within the style sheet

Must be declared at the top level of the style sheet, as a direct child of the <xsl:stylesheet> element

Must have a unique variable name Evaluated only once when stylesheet

is invoked

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Local variables

Referenced only within template Can share name with other local or

global variable Reevaluated when template is used

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Examples

average numbering

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Parameters

Similar to variables, but:Value can be changed after it is

declaredCan be set outside of scope

Syntax: <xsl:param name=“name” select=“value”/>

Example: <xsl:param name=”Filter” select=”'C103'” />

To reference: $param-name

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External parameters

Depends on XSLT processor Some work by appending parameter

value to url Command line processors allow

external parameter setting:MSXMLSaxon

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Template parameters

Local in scope Created inside <xsl:template>

element Used to pass parameters to template

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Idea

Called template contains param definitions

Calling template place <xsl:with-param> element in

<xsl:apply-templates> element or <xsl:call-template> element Syntax: <xsl:with-param name=“name”

select=“value”/> No error if calling param name does not

match template param name

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Named template

Template not associated with node set Collection of commands that are

accessed from other templates in the style sheet

Syntax: <xsl:template name="name">

XSLT elements

</xsl:template>

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Calling named templates

Syntax:

<xsl:call-template name=”name”>

<xsl:with-param />

<xsl:with-param />

...

</xsl:call-template>

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Example

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Functional programming

Functional programming language:Relies on the evaluation of functions

and expressions, not sequential execution of commands

Different from C family of languages• LISP, Scheme, ML

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Templates as functions

A template supplies a result fragmentincorporated into the final documentthink of this as substitutionfunction call replaced by result

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Iteration

How to handle iteration with templates?stars for ratings

Possibilitiesconvert numbers into node sets

• weird since node sets are supposed to come from the document

recursive templates

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Recursion

Recursionbase case

• when do I stop?

recursive case• how do I bite off one piece• call template again with the rest

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Example

Template: star(rating)desired output: # stars = # in rating

Base case:rating = 0output: nothing

Recursive caserating > 0output: * plus result of star (rating-1)

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Example, cont'd

star(3) replaced by * star(2) replaced by ** star(1) replaced by *** star(0) ***

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Pseudocode

stars (n)if n = 0 return ''else

• return '*' + stars(n-1)

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Recursive pattern

Syntax with <xsl:if>:<xsl:template name=”template_name”>

<xsl:param name=”param_name” select=”default_value” />

...

<xsl:if test=”stopping_condition”>

...

<xsl:call-template name=”template_name”>

<xsl:with-param name=”param_name” select=”new_value” />

</xsl:call-template>

...

</xsl:if>

</xsl:template>

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Example

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Another example

"best rated" jeep supplier Finding maximum

built into XSLT 2.0

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Recursive statement?

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What about the name?

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Homework #5

Case 1 from Chapter 7 Plus doing it "correctly" with CSS