Question

I have a following XML file:

<titles>
   <book title="XML Today" author="David Perry"/>
   <book title="XML and Microsoft" author="David Perry"/>
   <book title="XML Productivity" author="Jim Kim"/>
   <book title="XSLT 1.0" author="Albert Jones"/>
   <book title="XSLT 2.0" author="Albert Jones"/>
   <book title="XSLT Manual" author="Jane Doe"/>
</titles>

I want to eliminate some elements and apply the following XSLT:

    <?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl">

  <xsl:output method="xml" indent="yes"/>

  <xsl:key name="author1-search" match="book[starts-with(@author, 'David')]" use="@title"/>
  <xsl:template match="book [key('author1-search', @title)]" />

  <xsl:key name="author2-search" match="book[starts-with(@author, 'Jim')]" use="@title"/>
  <xsl:template match="book [key('author2-search', @title)]" />

  <xsl:template match="/">  
    <xsl:apply-templates />
  </xsl:template>

</xsl:stylesheet>

Is it possible to use an inline xsl variable

  <xsl:variable name="Author"> 
    <name>David</name> 
    <name>Jim</name> 
  </xsl:variable> 

instead of “author1-search”, “author2-search”, and so on to loop through names?

I can use only XSLT 1.0 (2.0 is currently not supported).

Thanks in advance,

Leo

Answer 1

No, patterns (in XSLT 1.0) cannot contain variable/parameter references.

One way to perform such a task would be like this:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="text"/>

 <xsl:param name="pAuthor" select="'David Perry'"/>

    <xsl:key name="kBookaByAuthor" match="book"
             use="@author"/>

    <xsl:template match="/">

     Books written by <xsl:value-of select="$pAuthor"/> :<xsl:text/>
        <xsl:apply-templates
             select="key('kBookaByAuthor', $pAuthor)"/>
    </xsl:template>

    <xsl:template match="book">
     <!-- One can do more formatting here -->
     <xsl:text>&#xA;     </xsl:text>
     <xsl:value-of select="@title"/>
    </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the provided XML document:

<titles>
    <book title="XML Today" author="David Perry"/>
    <book title="XML and Microsoft" author="David Perry"/>
    <book title="XML Productivity" author="Jim Kim"/>
    <book title="XSLT 1.0" author="Albert Jones"/>
    <book title="XSLT 2.0" author="Albert Jones"/>
    <book title="XSLT Manual" author="Jane Doe"/>
</titles>

the wanted, correct result is produced:

Books written by David Perry :
  XML Today
  XML and Microsoft

Update: In a comment the OP has clarified that:

“I thought I fully specified my requirements in the initial question.
As I mentioned in my question and in my first comment, it would be
helpful to me to see the approach for dealing with more than one
author“

Here is a solution that truly uses keys (note that the “key” in the answer by @Flynn1179 doesn’t build any index and is just a constant sequence of strings– so the function key() using that xsl:key is actually finding a string in a list of strings — which is O(N) as contrasted to, typically, O(1) for searching in a true index):

<xsl:stylesheet version="1.0"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
     xmlns:ext="http://exslt.org/common">

     <xsl:output method="text"/>

     <xsl:param name="pAuthors">
      <x>David Perry</x>
      <x>Jane Doe</x>
     </xsl:param>

     <xsl:variable name="vParams" select=
      "ext:node-set($pAuthors)/*"/>

     <xsl:key name="kBookByAuthor" match="book"
                     use="@author"/>

     <xsl:template match="/">
       Books written by : <xsl:text/>

       <xsl:apply-templates select="$vParams"/>

       <xsl:apply-templates select=
        "key('kBookByAuthor', $vParams)"/>
     </xsl:template>

     <xsl:template match="book">
       <!-- One can do more formatting here -->
       <xsl:text>&#xA;     </xsl:text>
       <xsl:value-of select="concat('&quot;', @title, '&quot;')"/>
     </xsl:template>

     <xsl:template match="x">
      <xsl:if test="not(position() = 1)">, </xsl:if>
      <xsl:value-of select="."/>
     </xsl:template>
</xsl:stylesheet>

When this transformation is applied to the provided XML document (above), the wanted, correct result is produced:

   Books written by : David Perry, Jane Doe
     "XML Today"
     "XML and Microsoft"
     "XSLT Manual"

Do note: In this solution the Exslt function node-set() is used. This is done only for convenience here. In a real usage, the value of the parameter will be specified externally and then the ext:node-set() function isn’t necessary.

Efficiency: This solution uses the true power of keys in XSLT. An experiment made using MSXML (3, 4 and 6) XSLT processors shows that if we search for 10000 authors the transformation time with different XSLT processors ranges from: 32ms to 45ms.

Interestingly, the solution presented by @Flynn1179 doesn’t indeed make key index and with many XSLT processors it takes (for the same number (10000) of authors) from 1044ms to 5564ms:

MSXML3: 5564 ms.,

MSXML4: 2526ms,

MSXML6: 4867 ms,

AltovaXML: 1044ms.

This is quite inferior to the performance one gets with true key indexing (32ms to 45ms).