XSLT grouping issue

Question

Hi,
We have SAP webAS 6.2.  I am trying to group the authors based on their name for each publisher. But I am getting wrong results. Can someone help me understand what I am doing wrong.
Thanks,
Suman
Source XML
<?xml version="1.0" encoding="utf-8"?>
<PublisherList>
    <publisher>
        <name>Penguin</name>
        <books>
            <book>
                <title>Title One</title>
                <author>David</author>
            </book>
            <book>
                <title>Title Two</title>
                <author>John</author>
            </book>
            <book>
                <title>Title Three</title>
                <author>John</author>
            </book>
            <book>
                <title>Title Four</title>
                <author>David</author>
            </book>
        </books>
    </publisher>
    <publisher>
        <name>Wrox</name>
        <books>
            <book>
                <title>Title Five</title>
                <author>David</author>
            </book>
            <book>
                <title>Title Six</title>
                <author>John</author>
            </book>
            <book>
                <title>Title Seven</title>
                <author>John</author>
            </book>
            <book>
                <title>Title Eight</title>
                <author>David</author>
            </book>
        </books>
    </publisher>
</PublisherList>
Transformation xslt:
<?xml version="1.0" encoding="utf-8"?>
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:output method="xml" indent="yes"/>
  <xsl:key name="Author" match="publisher/books/book" use="author"/>
  <xsl:template match="PublisherList">
    <List>
     <xsl:apply-templates select="publisher/books"/>
    </List>
  </xsl:template>
  <xsl:template match="books">
    <xsl:for-each select="book[generate-id(.) = generate-id(key('Author', author)[1])]">
      <xsl:sort select="author"/>
      <BookPublisher>
        <name>
          <xsl:value-of select="//parent::node()[name()='publisher']/name"/>
        </name>
        <BooksByAuthor>
          <AuthorName><xsl:value-of select="author"/></AuthorName>
         <xsl:for-each select="key('Author', author)">
          <title>
            <xsl:value-of select="title"/>
          </title>
        </xsl:for-each>
        </BooksByAuthor>
      </BookPublisher>
    </xsl:for-each>
  </xsl:template>
</xsl:transform>
Expected Result:
<?xml version="1.0" encoding="UTF-8"?>
<List>
    <BookPublisher>
        <name>Penguin</name>
        <BooksByAuthor>
            <AuthorName>David</AuthorName>
            <title>Title One</title>
            <title>Title Four</title>
        </BooksByAuthor>
        <BooksByAuthor>
            <AuthorName>John</AuthorName>
            <title>Title Two</title>
            <title>Title Three</title>
        </BooksByAuthor>
    </BookPublisher>
    <BookPublisher>
        <name>Wrox</name>
        <BooksByAuthor>
            <AuthorName>David</AuthorName>
            <title>Title Five</title>
            <title>Title Eight</title>
        </BooksByAuthor>
        <BooksByAuthor>
            <AuthorName>John</AuthorName>
            <title>Title Six</title>
            <title>Title Seven</title>
        </BooksByAuthor>
    </BookPublisher>
</List>
Actual Result from my xslt:
<?xml version="1.0" encoding="UTF-8"?>
<List>
    <BookPublisher>
        <name>Penguin</name>
        <BooksByAuthor>
            <AuthorName>David</AuthorName>
            <title>Title One</title>
            <title>Title Four</title>
            <title>Title Five</title>
            <title>Title Eight</title>
        </BooksByAuthor>
    </BookPublisher>
    <BookPublisher>
        <name>Penguin</name>
        <BooksByAuthor>
            <AuthorName>John</AuthorName>
            <title>Title Two</title>
            <title>Title Three</title>
            <title>Title Six</title>
            <title>Title Seven</title>
        </BooksByAuthor>
    </BookPublisher>
</List>

Answer 1

I got the answer from MSDN forum for this.
Here is the code
<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
      <xsl:output method="xml" indent="yes"/>
      <xsl:key name="Author" match="publisher/books/book" use="author"/>
      <xsl:template match="PublisherList">
            <List>
                  <xsl:apply-templates select="publisher"/>
            </List>
      </xsl:template>
      <xsl:template match="publisher">
      <BookPublisher>
                        <name>
                              <xsl:value-of select="name"/>
                        </name>
            <xsl:for-each select= "books/book[generate-id(.)=generate-id(key('Author', author)[../../name = current()/name][1])]">
                  <xsl:sort select="author"/>
                         <BooksByAuthor>
                              <AuthorName>
                                    <xsl:value-of select="author"/>
                              </AuthorName>
                              <xsl:for-each select= "key('Author', author)[../../name = current()/../../name]">
                                    <title>
                                          <xsl:value-of select="title"/>
                                    </title>
                              </xsl:for-each>
                        </BooksByAuthor>
                       </xsl:for-each>
             </BookPublisher>
      </xsl:template>
</xsl:transform>