Re: Question on duplicate node elimination

Michael Kay
Saxonica

Hello,

I have a question on duplicate node elimination.

> From the XPATH 1.0 specification:
...
* node-set (an unordered collection of nodes without duplicates)
...
An initial sequence of steps is composed together with a following step as
follows. The initial sequence of steps selects a set of nodes relative to a
context node. Each node in that set is used as a context node for the
following step. The sets of nodes identified by that step are unioned
together. The set of nodes identified by the composition of the steps is
this union.
...

So "are unioned together" results in a node-set and that does not contain
duplicates.

Now how can this algorithm step be realized in XPATH 1.0 plus
exslt:node-set
funtion?
(this would work in browsers with the technique from David Carlisle [1])

This is the output for below stylesheet simple.xsl on file simple.xml.
For the nodes four node /a/b/c their parents are copied into an
intermediate
result. But xsltproc and xalan show that the four nodes are different by
the
their generate-id() values, whereas the first pair and last pair are
representations of the same node.

xsltproc        xalan
1: id2659470    1: AbT0
2: id2659470    2: AbT0
3: id2659354    3: AbT1
4: id2659354    4: AbT1

1: id2659234    1: AbT2
2: id2659244    2: AbT3
3: id2659254    3: AbT4
4: id2659264    4: AbT5

1:<b>           1:<b>
     <c>1</c>         <c>1</c>
     <c>2</c>         <c>2</c>
   </b>             </b>
2:<b>           2:<b>
     <c>1</c>         <c>1</c>
     <c>2</c>         <c>2</c>
   </b>             </b>
3:<b>           3:<b>
     <c>1</c>         <c>1</c>
     <c>2</c>         <c>2</c>
   </b>             </b>
4:<b>           4:<b>
     <c>1</c>         <c>1</c>
     <c>2</c>         <c>2</c>
   </b>             </b>

$ cat simple.xml
<a>
<b>
<c>1</c>
<c>2</c>
</b>
<b>
<c>1</c>
<c>2</c>
</b>
</a>
$ cat simple.xsl
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exsl="http://exslt.org/common"

<xsl:output omit-xml-declaration="yes"/>

   <xsl:template match="/">
     <xsl:variable name="rtf">
       <xsl:for-each select="/a/b/c">
         <xsl:copy-of select=".."/>
       </xsl:for-each>
     </xsl:variable>

     <xsl:for-each select="/a/b/c">
       <xsl:value-of select="position()"/><xsl:text>:</xsl:text>
       <xsl:value-of select="generate-id(..)"/><xsl:text>&#10;</xsl:text>
     </xsl:for-each>

<xsl:text>&#10;</xsl:text>

     <xsl:for-each select="exsl:node-set($rtf)/*">
       <xsl:value-of select="position()"/><xsl:text>:</xsl:text>
       <xsl:value-of select="generate-id(.)"/><xsl:text>&#10;</xsl:text>
     </xsl:for-each>

<xsl:text>&#10;</xsl:text>

     <xsl:for-each select="exsl:node-set($rtf)/*">
       <xsl:value-of select="position()"/><xsl:text>:</xsl:text>
       <xsl:copy-of select="."/><xsl:text>&#10;</xsl:text>
     </xsl:for-each>
   </xsl:template>

</xsl:stylesheet>
$

[1] http://dpcarlisle.blogspot.com/2007/05/exslt-node-set-function.html


Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Developer, XML Compiler, L3
WebSphere DataPower SOA Appliances
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