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Re: Question on duplicate node elimination

Subject: Re: Question on duplicate node elimination
From: Hermann Stamm-Wilbrandt <STAMMW@xxxxxxxxxx>
Date: Mon, 23 Aug 2010 00:12:41 +0200
Re:  Question on duplicate node elimination
> I'm not sure what you find surprising about the results you are seeing.
> What results would you expect?
Not surprising.

But how could the algorithm step of "duplicate elimination" be done?
How can the duplicates be determined and removed, correctly?

Perhaps I was not clear enough with my question.
How can this step (p. 40 from [1]) be implemented in XPath 1.0 plus
eslt:node-set():
A location step identifies a new mode-set relative to the context node-set.
The location step is evaluated against each node in the context node-set,
and the union of the resulting node-sets becomes the context node-set for
the next step. Location steps consist of an axis identifier, a node test
and zero or more predicates (see Figure 3-4). ...


[1]
http://www.theserverside.net/tt/books/addisonwesley/EssentialXML/index.tss

Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Developer, XML Compiler, L3
WebSphere DataPower SOA Appliances
----------------------------------------------------------------------
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Martin Jetter
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294



From:       Michael Kay <mike@xxxxxxxxxxxx>
To:         xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Date:       08/22/2010 11:53 PM
Subject:    Re:  Question on duplicate node elimination



I'm not sure what you find surprising about the results you are seeing.
What results would you expect?

xsl:copy-of creates a new node. Copying the same node twice creates two
copies with distinct identity. Is that the issue?

Michael Kay
Saxonica

On 22/08/2010 22:25, Hermann Stamm-Wilbrandt wrote:
> 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
> ----------------------------------------------------------------------
> IBM Deutschland Research&  Development GmbH
> Vorsitzender des Aufsichtsrats: Martin Jetter
> Geschaeftsfuehrung: Dirk Wittkopp
> Sitz der Gesellschaft: Boeblingen
> Registergericht: Amtsgericht Stuttgart, HRB 243294

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