presentation: XSLT Assessment Questions
image-directory: cocoon-images

Author: Aidan Killian, Martin Dransfield, Warrell Harries

For: Wiley Interscience/SCS

Date: August 2007

Assessment of XSLT Knowledge

slide: XSLT Variables

Variable 1

code:
<xsl:variable name="cost">
	<xsl:value-of select="sum(/statement/item/amount)"/>
</xsl:variable>

Variable 2

code:
<xsl:variable name="cost" select="sum(/statement/item/amount)"/>

subtitle: 1.1 What is the difference between Variable 1 & 2 above? 

Variable 1 holds a result tree fragment with a root node and a text node with string value the decimal representation of a number
Variable 2 holds a number

2 points

subtitle: 1.2 Why would you use one rather than the other?

Variable 2 is simpler and much easier to use in XSLT 1.0

1 points

subtitle: 1.3 What is special about XSLT Variables? 

Variable are assigned once and cannot have their value changed

2 points

subtitle: 1.4 Why is this behaviour thought to be desirable?
Transparency - it is far easier to reason about a program that is free from side effects. So you can prove your program is correct with less effort.
Scalability - pure (side-effect free) programs are much easier to parallelize
Debugging - no need to monitor when a variable changes value.

3 Points

code:
<things>
	<thing>
		<quantity>1</quantity>
		<price>2</price>
	</thing>
	<thing>
		<quantity>4</quantity>
		<price>5</price>
	</thing>
	<thing>
		<quantity>3</quantity>
		<price>10</price>
	</thing>
	<thing>
		<quantity>2</quantity>
		<price>1</price>
	</thing>
</things>

subtitle: 1.3 Please declare and initialise a variable that can be used to total the cost of things.

 <xsl:variable name="x">
   <xsl:for-each select="things/thing">
	<xsl:value-of select="quantity * price"/>
   </xsl:for-each>
 </xsl:variable>
 
4 points 

slide: XSLT Features

subtitle: 2.1 Please summarise the difference between 'Push' and 'Pull' usage in XSLT? 

A 'Pull' implementation prefers the use of <xsl:call-template> over the use of <xsl:apply-templates>

2 points

subtitle: 2.2 Please describe four differences between XSLT v1.0 and v2.0?

New options for the grouping of nodes: the xsl:for-each-group instruction and the current-group() function have been added.
Users can create and use custom functions in the stylesheet
The possibility of generating multiple output documents have been extended in comparison to XSLT 1.1. You can also link between these 'result trees'.
XHTML output method has been added.
There is a new xsl:sort-key declaration.
The possibility to create a temporary tree on which to perform actions.
A new instruction xsl:namespace has been added to generate namespace nodes.

4 points

slide: Template Usage

code:
<xsl:template name="proc">
   <xsl:param name="txt" select="''"/>
   <value>
      <xsl:choose>
         <xsl:when test="contains($txt, '|')" >
            <xsl:value-of select="substring-before($txt, '|')"/>
         </xsl:when>
         <xsl:otherwise>
            <xsl:value-of select="$txt"/>
         </xsl:otherwise>
      </xsl:choose>
   </value>
   <xsl:variable name="left" select="substring-after($txt, '|')"/>
   <xsl:if test="string-length($left)>1" >
      <xsl:call-template name="proc" >
         <xsl:with-param name="txt" select="$left"/>
      </xsl:call-template>
   </xsl:if>
</xsl:template>

subtitle: 3.1 In the template above name the computing technique being used?

Recursion

1 points

subtitle: 3.2 Please give one benefit and one disadvantage of this technique
Benefit
Generates new variables on each iteration
Disadvantage
Resource hungry

2 points

code:
<xsl:template match="h:parameter[@name='order']/h:value">
   <xsl:variable name="values">
      <xsl:call-template name="proc" >
         <xsl:with-param name="txt" select="text()"/>
      </xsl:call-template>
   </xsl:variable>
   <xsl:for-each select="xalan:nodeset($values)/value">
      <SetGroupTitleJournalOrder group="1" title="{.}" sort="{position()}"/>
   </xsl:for-each>
</xsl:template>

subtitle: 3.2 In the XSL 1.0 template above describe the purpose of xalan:nodeset?

It's a XalanJ extension function that allows processing of result tree fragments in XSLT 1.0

subtitle: 3.3 Why is the following stylesheet often used by XSL developers?

code:
<?xml version="1.0"?> 
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*"/>
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>

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slide: XPath

subtitle: 4.1 When might you use current() rather than '.' when selecting a node?

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img_fullWidth: xmlTree.jpg

subtitle: 4.2 Please write an XPath expression that returns the contents of all p elements that follow the one with ID="p13" 

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