Joins and Query Use with XML - 9.6 Implementing the W3C XML Query-Use Cases in XSLT
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Problem

You need to perform a query operation similar to one of the use cases in http://www.w3.org/TR/2001/WD-xmlquery-use-cases-20011220, but you want to use XSLT rather than XQuery (http://www.w3.org/TR/xquery/).

Solution

The following examples are XSLT solutions to most of the XML query-use cases presented in the W3C document. The descriptions of each use case are taken almost verbatim from the W3C document.

Use case “XMP”: experiences and exemplars.

This use case contains several example queries that illustrate requirements gathered by the W3C from the database and document communities. The data use by these queries follows in Examples 9-10 to Example 9-13.

Example 9-10. bib.xml

<bib>
    <book year="1994">
        <title>TCP/IP Illustrated</title>             
        <author><last>Stevens</last> 
<first>W. </first></author> 
        <publisher>Addison-Wesley</publisher>
        <price> 65.95</price>
     </book>

     <book year="1992">
        <title>Advanced Programming in the Unix environment</title> 
        <author><last>Stevens</last><first>W. </first></author>
        <publisher>Addison-Wesley</publisher>
        <price>65.95</price>
     </book>

     <book year="2000">
        <title>Data on the Web</title>
        <author><last>Abiteboul </last><first> Serge</first></author> 
        <author><last>Buneman</last><first> Peter</first></author>
        <author><last>Suciu </last><first>Dan </first></author>
        <publisher>Morgan Kaufmann Publishers</publisher>
        <price> 39.95</price>
     </book>

     <book year="1999">
        <title>The Economics of Technology and Content for Digital TV</title> 
        <editor>
               <last>Gerbarg</last> <first>Darcy</first>          
                 <affiliation>CITI </affiliation>
        </editor>
           <publisher>Kluwer Academic Publishers</publisher>
        <price>129.95</price>
     </book>

</bib>

Example 9-11. reviews.xml

reviews>
    <entry>
        <title>Data on the Web</title>
        <price>34.95</price>
        <review>
               A very good discussion of semi-structured database
               systems and XML.
        </review>
    </entry>
    <entry>
        <title>Advanced Programming in the Unix environment</title>
        <price>65.95</price>
        <review>
               A clear and detailed discussion of UNIX programming.
        </review>
    </entry>
    <entry>
        <title>TCP/IP Illustrated</title>
        <price>65.95</price>
        <review>
               One of the best books on TCP/IP.
        </review>
    </entry>
</reviews>

Example 9-12. books.xml

<chapter>
    <title>Data Model</title>
    <section>
        <title>Syntax For Data Model</title>
    </section>
    <section>
        <title>XML</title>
        <section>
            <title>Basic Syntax</title>
        </section>
        <section>
            <title>XML and Semistructured Data</title>
        </section>
    </section>
</chapter>

Example 9-13. prices.xml

<prices>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <source>www.amazon.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <source>www.bn.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title> TCP/IP Illustrated </title>
        <source>www.amazon.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title> TCP/IP Illustrated </title>
        <source>www.bn.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>www.amazon.com</source>
        <price>34.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>www.bn.com</source>
        <price>39.95</price>
    </book>
</prices>
Question 1. List books in bib.xml published by Addison-Wesley after 1991, including
their year and title: <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:import href="copy.xslt"/>

<xsl:template match="book[publisher = 'Addison-Wesley' and @year > 1991]">
  <xsl:copy-of select="."/> </xsl:template>

<xsl:template match="book"/>

</xsl:stylesheet>
Question 2. Create a flat list of all the title-author pairs from bib.xml, with each
pair enclosed in a "result" element:
<xsl:template match="/">
<results>
  <xsl:apply-templates select="bib/book/author"/>
</results>
</xsl:template>

<xsl:template match="author">
  <result>
    <xsl:copy-of select="preceding-sibling::title"/>
    <xsl:copy-of select="."/>
  </result>
</xsl:template>
Question 3. For each book in bib.xml, list the title and authors, grouped inside a
"result" element:
<xsl:template match="bib">
  <results>
    <xsl:for-each select="book">
    <result>
      <xsl:copy-of select="title"/>
      <xsl:copy-of select="author"/>
    </result>
  </xsl:for-each>
 </results>
</xsl:template>
Question 4. For each author in bib.xml, list the author's name and the titles of all
books by that author, grouped inside a "result" element: <xsl:template match="/">
<results>
  <xsl:for-each select="//author[not(.=preceding::author)]">
    <result>
      <xsl:copy-of select="."/>
      <xsl:for-each select="/bib/book[author=current()]">
        <xsl:copy-of select="title"/>
      </xsl:for-each>
    </result>
  </xsl:for-each>
  </results>
Question 5. For each book found on both http://www.bn.com (bib.xml) and http://www.
amazon.com (reviews.xml), list the title of the book and its price from each source:
<xsl:variable name="bn" select="document('bib.xml')"/> <xsl:variable name="amazon" select="document('reviews.xml')"/>

<!--Solution 1 -->
<xsl:template match="/">
  <books-with-prices>
  <xsl:for-each select="$bn//book[title = $amazon//entry/title]">
    <book-with-prices>
      <xsl:copy-of select="title"/>
      <price-amazon><xsl:value-of
      select="$amazon//entry[title=current()/title]/price"/></price-amazon>
      <price-bn><xsl:value-of select="price"/></price-bn>
    </book-with-prices>
  </xsl:for-each>
  </books-with-prices>
</xsl:template>

<!--Solution 2-->
<xsl:template match="/">
  <books-with-prices>
  <xsl:for-each select="$bn/book">
    <xsl:variable name="bn-book" select="."/>
    <xsl:for-each select="$amazon//entry[title=$bn-book/title]">
      <book-with-prices>
        <xsl:copy-of select="title"/>
        <price-amazon><xsl:value-of select="price"/></price-amazon>
        <price-bn><xsl:value-of select="$bn-book/price"/></price-bn>
      </book-with-prices>
    </xsl:for-each>
  </xsl:for-each>
  </books-with-prices>
</xsl:template>
Question 6. For each book that has at least one author, list the title and first two
authors, as well as an empty
"et-al" element if the book has additional authors:
<xsl:template match="bib">
  <xsl:copy>
    <xsl:for-each select="book[author]">
      <xsl:copy>
        <xsl:copy-of select="title"/>
        <xsl:copy-of select="author[position() &lt;= 2]"/>
        <xsl:if test="author[3]">
        <et-al/>
        </xsl:if>
      </xsl:copy>
    </xsl:for-each>
  </xsl:copy>
</xsl:template>
Question 7. List the titles and years of all books published by Addison-Wesley after
1991, in alphabetic order: <xsl:template match="bib">
  <xsl:copy>
    <xsl:for-each select="book[publisher = 'Addison-Wesley'
          and @year > 1991]">
      <xsl:sort select="title"/>
      <xsl:copy>
        <xsl:copy-of select="@year"/>
        <xsl:copy-of select="title"/>
      </xsl:copy>
    </xsl:for-each>
  </xsl:copy>
</xsl:template>
Question 8. In the document books.xml, find all section or chapter titles that
contain the word "XML", regardless of the nesting level:
 <xsl:template match="/">
<results>
  <xsl:copy-of select="(//chapter/title |
  //section/title)[contains(.,'XML')]"/>
</results>
</xsl:template>
Question 9. In the document prices.xml, find the minimum price for each book in the
form of a "minprice" element with the book title as its title attribute:
<xsl:include href="../math/math.min.xslt"/>

<xsl:template match="/">
<results>
  <xsl:for-each select="//book/title[not(. = ./preceding::title)]">
    <xsl:variable name="min-price">
      <xsl:call-template name="math:min">
        <xsl:with-param name="nodes" select="//book[title =
                    current()]/price"/>
      </xsl:call-template>
    </xsl:variable>
    <minprice title="{.}">
      <price><xsl:value-of select="$min-price"/></prices>
    </minprice>
  </xsl:for-each>
</results>
</xsl:template>
Question 10. For each book with an author, return the book with its title and
authors. For each book with an editor, return a reference with the book title and the
editor's affiliation:
<xsl:template match="bib"> <xsl:copy>
  <xsl:for-each select="book[author]">
    <xsl:copy>
      <xsl:copy-of select="title"/>
      <xsl:copy-of select="author"/>
    </xsl:copy>
  </xsl:for-each>

  <xsl:for-each select="book[editor]">
    <reference>
      <xsl:copy-of select="title"/>
      <org><xsl:value-of select="editor/affiliation"/></org>
    </reference>
  </xsl:for-each>
  </xsl:copy>
</xsl:template>
Question 11. Find pairs of books that have different titles but the same set of
authors (possibly in a different order):
<xsl:include href="query.equal-values.xslt"/>

<xsl:template match="bib">
  <xsl:copy>
    <xsl:for-each select="book[author]">
      <xsl:variable name="book1" select="."/>
      <xsl:for-each select="./following-sibling::book[author]">
        <xsl:variable name="same-authors">
          <xsl:call-template name="query:equal-values">
            <xsl:with-param name="nodes1" select="$book1/author"/>
            <xsl:with-param name="nodes2" select="author"/> 
          </xsl:call-template>
        </xsl:variable>
        <xsl:if test="string($same-authors)">
          <book-pair>
            <xsl:copy-of select="$book1/title"/>
            <xsl:copy-of select="title"/>
          </book-pair>
        </xsl:if>
      </xsl:for-each>
    </xsl:for-each>
  </xsl:copy>
</xsl:template> 

Next: Use case TREE: queries that preserve hierarchy >>
 

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