XML Tutorial/XPath/proceding sibling

First subject preceding Java is

File: Data.xml
<?xml version = "1.0"?>
<product>
   <books>
      <book>
         Getting Started with Microsoft Visual C++ 
      </book>
      <book>Java</book>
   </books>
</product>
File: Transform.xslt
<?xml version = "1.0"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/product">
    First subject preceding "Java" is
    <xsl:value-of
      select="//subject[. = "Java"
                  ]/preceding-sibling::subject[ 1 ]" />
  </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?>
    First subject preceding "Java" is

if test="not(preceding-sibling::address[zip=$lastZip])"

File: Data.xml
<?xml version="1.0"?>
<addressbook>
  <address>
    <name>
      <title>Mr.</title>
      <first-name>Jack</first-name>
      <last-name>Smith</last-name>
    </name>
    <street>1234 Main Street</street>
    <city>New York</city>
    <state>WI</state>
    <zip>48392</zip>
  </address>
</addressbook>

File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text" indent="no"/>
  <xsl:template match="/">
    <xsl:for-each select="addressbook/address">
      <xsl:sort select="zip"/>
      <xsl:variable name="lastZip" select="zip"/>
      <xsl:if test="not(preceding-sibling::address[zip=$lastZip])">
        <xsl:text>Zip code </xsl:text>
        <xsl:value-of select="zip"/>
        <xsl:text>: &#xA;</xsl:text>
        <xsl:for-each select="/addressbook/address[zip=$lastZip]">
          <xsl:sort select="name/last-name"/>
          <xsl:sort select="name/first-name"/>
          <xsl:if test="name/title">
            <xsl:value-of select="name/title"/>
            <xsl:text> </xsl:text>
          </xsl:if>
          <xsl:value-of select="name/first-name"/>
          <xsl:text> </xsl:text>
          <xsl:value-of select="name/last-name"/>
          <xsl:text>&#xA;</xsl:text>
          <xsl:value-of select="street"/>
          <xsl:text>&#xA;&#xA;</xsl:text>
        </xsl:for-each>
      </xsl:if>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>
Output:
Zip code 48392: 
Mr. Jack Smith
1234 Main Street

if test="position() = 1 or zip!=preceding-sibling::address[1]/zip"

File: Data.xml
<?xml version="1.0"?>
<addressbook>
  <address>
    <name>
      <title>Mr.</title>
      <first-name>Jack</first-name>
      <last-name>Smith</last-name>
    </name>
    <street>1234 Main Street</street>
    <city>New York</city>
    <state>WI</state>
    <zip>48392</zip>
  </address>
</addressbook>

File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text" indent="no"/>
  <xsl:template match="/">
    <xsl:for-each select="addressbook/address">
      <xsl:sort select="zip"/>
      <xsl:if test="position() = 1 or zip!=preceding-sibling::address[1]/zip">
        <xsl:text>&#xA;Zip code </xsl:text>
        <xsl:value-of select="zip"/>
        <xsl:text> (</xsl:text>
        <xsl:value-of select="city"/>
        <xsl:text>, </xsl:text>
        <xsl:value-of select="state"/>
        <xsl:text>): &#xA;</xsl:text>
      </xsl:if>
      <xsl:if test="name/title">
        <xsl:value-of select="name/title"/>
        <xsl:text> </xsl:text>
      </xsl:if>
      <xsl:value-of select="name/first-name"/>
      <xsl:text> </xsl:text>
      <xsl:value-of select="name/last-name"/>
      <xsl:text>&#xA;</xsl:text>
      <xsl:value-of select="street"/>
      <xsl:text>&#xA;&#xA;</xsl:text>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>
Output:

Zip code 48392 (New York, WI): 
Mr. Jack Smith
1234 Main Street

preceding-sibling axis includes those nodes that are in the preceding axis and that also share a parent node with the context node.

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<data>
    <AAA id="a1" pos="start">
      <BBB id="b1"/>
      <BBB id="b2"/>
    </AAA>
    <AAA id="a2">
      <BBB id="b3"/>
      <BBB id="b4"/>
      <CCC id="c1">
        <CCC id="c2"/>
      </CCC>
      <BBB id="b5">
        <CCC id="c3"/>
      </BBB>
    </AAA>
</data>
File: Transform.xslt
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
      version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
      <table border="1" cellpadding="6">
        <tr>
          <th colspan="2">Axis: preceding-sibling</th>
        </tr>
        <tr>
          <td>Element</th>
          <td>Node-set</th>
        </tr>
        <xsl:for-each select="/source//*">
          <xsl:call-template name="print"/>
        </xsl:for-each>
      </table>
    </xsl:template>
    <xsl:template name="print">
      <tr>
        <td>
          <xsl:value-of select="name()"/>
          <xsl:text> id = </xsl:text>
          <xsl:value-of select="./@id"/>
        </td>
        <td>
          <xsl:for-each select="preceding-sibling::*">
            <xsl:if test="not(@id)">
              <xsl:value-of select="name()"/>
            </xsl:if>
            <xsl:value-of select="./@id"/>
            <xsl:text/>
          </xsl:for-each>
        </td>
      </tr>
    </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?><table border="1" cellpadding="6"><tr><th colspan="2">Axis: preceding-sibling</th></tr><tr><td>Element</th><td>Node-set</th></tr></table>