XSLT merging help

[vez yao]

Hello, i'm fairly new to xsl stylesheets but have always wanted to know how to merge two xml documents and transform them to output a xml document referencing certain elements.
I've written up two simple xml documents to help you guys understand what i am after.

authors.xml:

<authors>
  <author>
    <name>Stefani, Josepi</name>
    <born>Milan, Italy</born-died>
    <nationality>Italian</nationality>
    <about_me>loves writing and reading</about_me>
  </author>
  <author>
    <name>Yu, Michael</name>
    <born>Guanzhou, China</born>
    <nationality>Chinese</nationality>
    <about_me>Caring person that spends his time writing</about_me>
  </author>
 </authors>

books.xml:

<books>
  <book>
    <title>Hello Children!</title>
    <author>Yu, Michael</author>
    <published_date>2007</published_date>
    <description>Uplifting and inspirational children's book</description>
    <price>15</price>
    <genre>children</genre>
    <type>picture book</type>
  </book>
  <book>
    <title>Over the Seas</title>
    <author>John, Gabbi</author>
    <date>2008</date>
    <drescription>Sweet and melodic tale between two lovers</description>
    <price>25</price>
    <genre>romance</genre>
    <type>novel</type>
  </book>
  <book>
    <title>In the Willows</title>
    <author>Yu, Michael</author>
    <published_date>1999</published_date>
    <description>Cheerful and full of wonderful animals</description>
    <price>17</price>
    <genre>children</genre>
    <type>picture book</type>
  </book>
 </books>

And the output that i'd like:

<authors>
  <author>
    <name>Stefani, Josepi</name>
    <born>Milan, Italy</born-died>
    <nationality>Italian</nationality>
    <about_me>loves writing and reading</about_me> 
      <books genre="romance">
         <book published_date="2008">
            <title>Over the Seas</title>
            <drescription>Sweet and melodic tale between two lovers</description>
            <price>25</price>
         </book>
      </books>
   </author>
   <author>
    <name>Yu, Michael</name>
    <born>Guanzhou, China</born-died>
    <nationality>Chinese</nationality>
    <about_me>Caring person that spends his time writing</about_me>
      <books genre="children">
         <book published_date="1999">
            <title>In the Willows</title>
            <description>Cheerful and full of wonderful animals</description>
            <price>17</price>
         </book>
		 <book published_date="2007">
            <title>Hello Children!</title>
            <description>Uplifting and inspirational children's book</description>
			<price>15</price>
         </book>
      </books>
	</author>
<authors>

So basically the books.xml 'author' element is a foreign key that references the authors.xml author entries. (i'm assuming using muenchian?)
- For each author, "name", "born", "nationality" and "about_me" along with all their "books".
- The books are grouped by "genre" and then sorted on "published_date".
- For each book, the "title", "description, "price" will be stored also.

Thanks

[Paul Clapham]

The document() function allows you to reference a second XML document from XSLT.

[g tsuji]

[0] I can show you how to do that, but before doing that, I do not target the output document in exactly the same as what you propose, in particular, I will not put the genre into the attribute to books (as the same author can write different genre of books). Instead I would show the demo with genre put in the book instead.

[0.1] There are quite a few typo and/or consistency in tagging in the sample. I only take the spirit of it and use a consistently named sample (like date vs published_date).

[0.2] Apart from that, the techniques being used to achieve the result are sufficiently varying so that any change of mind can easily be done by yourself with the techniques as demonstrated.

[1] Here is the xsl document. It is supposed to operate on authors.xml and that the books.xml is in the same directory as authors.xml.

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:param name="ext_xml" select="'books.xml'" />
<xsl:output method="xml" encoding="utf-8" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:template match="node()|@*|text()|comment()|processing-instruction()">
    <xsl:copy>
        <xsl:apply-templates select="node()|@*|text()|comment()|processing-instruction()" />
    </xsl:copy>
</xsl:template>
<xsl:template match="author">
    <xsl:copy>
        <xsl:apply-templates select="node()|@*|text()|comment()|processing-instruction()" />
        <xsl:variable name="current_author" select="name" />
        <xsl:variable name="ext" select="document($ext_xml)/books/book[author = $current_author]" />
        <xsl:if test="$ext">
            <books>
                <xsl:for-each select="$ext">
                    <xsl:call-template name="process_copy">
                        <xsl:with-param name="root" select="." />
                    </xsl:call-template>
                </xsl:for-each>
            </books>
        </xsl:if>
    </xsl:copy>
</xsl:template>
<xsl:template name="process_copy">
    <xsl:param name="root" />
        <xsl:if test="name($root) != 'author'">
            <xsl:choose>
                <xsl:when test="name($root) = 'book'">
                    <xsl:copy>
                        <xsl:attribute name="genre">
                            <xsl:value-of select="genre" />
                        </xsl:attribute>
                        <xsl:attribute name="published_date">
                            <xsl:value-of select="published_date" />
                        </xsl:attribute>
                        <xsl:for-each select="node()[name() != 'genre' and name() != 'published_date'] |@*|text()">
                            <xsl:call-template name="process_copy">
                                <xsl:with-param name="root" select="." />
                            </xsl:call-template>
                        </xsl:for-each>
                    </xsl:copy>
                </xsl:when>
                <xsl:when test="name($root) = 'type'">
                </xsl:when>
                <xsl:otherwise>
                    <xsl:copy>
                        <xsl:for-each select="node()|@*|text()">
                            <xsl:call-template name="process_copy">
                                <xsl:with-param name="root" select="." />
                            </xsl:call-template>
                        </xsl:for-each>
                    </xsl:copy>
                </xsl:otherwise>
            </xsl:choose>
        </xsl:if>
</xsl:template>
		
</xsl:stylesheet>

[1.1] I suppose there always exist genre and published_date. In case one or both might be absent, it is easy to add a node test with xsl:if to filter the cases.