Re: [xsl] How to do this tricky elimination on XML using XSL

I think I would tackle this in two passes. First use xsl:for-each-group to identify the nodes to be removed; then do a modified identity transform that retains only the nodes not in this list.

The first pass is something like this:

 <xsl:variable name="removed-nodes" as="element(*)*"> <xsl:for-each-group select="//blockA/*" group-by="concat(@id, '~', @method, '~', otherchild)"> <xsl:sequence select="subsequence(current-group(), 2)"/> </xsl:for-each-group> </xsl:variable>

The second pass is:

<xsl:template match="*">
<xsl:if test="empty(. intersect $removed-nodes)">
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:if>
</xsl:template>

Michael Kay
Saxonica

On 19/06/2012 10:14, Jo Na wrote:

Hi,
I have this input xml:
     <map>
         <region>
             <gridA id="1">
                 <blockA id="01" method="build">
                     <building1 id="x" method="build">
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be removed -->
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="01">
                     <building1 id="x" method="modify">
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be kept (prev node have same id but diff method so it's not
considered as successive -->
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="02">
                     <building3 id="y" method="modify">
                         <otherchild>b</otherchild>
                     </building3>
                     <building2 id="x" method="demolish"/>
                 </blockA>

                 <blockA id="01">
                     <building1 id="y" method="build">  <!-- this one
will be kept (diff id) -->
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be removed -->
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="02">
                     <building3 id="y" method="modify">  <!-- this one
will be removed -->
                         <otherchild>b</otherchild>
                     </building3>
                     <building2 id="x" method="demolish"/>  <!-- this
one will be removed -->
                 </blockA>
             </gridA>

             <gridA id="2">
                 <blockA id="01" method="build">
                     <building1 id="x" method="build">
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be removed -->
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be kept (diff children) -->
                         <otherchild>b</otherchild>
                     </building1>
                 </blockA>
                 <blockA id="01">
                     <building1 id="x" method="build">  <!-- this one
will be removed -->
                         <otherchild>b</otherchild>
                     </building1>
                 </blockA>
             </gridA>
             <gridB id="1">
                 ...and so on..
             </gridB>
         </region>
     </map>

Expected Output:

     <map>
         <region>
             <gridA id="1">
                 <blockA id="01" method="build">
                     <building1 id="x" method="build">
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="01">
                     <building1 id="x" method="modify">
                         <otherchild>a</otherchild>
                     </building1>
                     <building1 id="x" method="build">  <!-- this one
will be kept (prev node have same id but diff method so it's not
considered as successive -->
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="02">
                     <building3 id="y" method="modify">
                         <otherchild>b</otherchild>
                     </building3>
                     <building2 id="x" method="demolish"/>
                 </blockA>

                 <blockA id="01">
                     <building1 id="y" method="build">  <!-- this one
will be kept (diff id) -->
                         <otherchild>a</otherchild>
                     </building1>
                 </blockA>

                 <blockA id="02"/>
             </gridA>

             <gridA id="2">
                 <blockA id="01" method="build">
                     <building1 id="x" method="build">
                         <otherchild>a</otherchild>
                     </building1>

                     <building1 id="x" method="build">  <!-- this one
will be kept (diff children) -->
                         <otherchild>b</otherchild>
                     </building1>
                 </blockA>
                 <blockA id="01"/>
             </gridA>
             <gridB id="1">
                 ...and so on..
             </gridB>
         </region>
     </map>
The XSLT so far:

     <xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
         <xsl:output indent="yes"/>  <xsl:strip-space elements="*"/>

         <xsl:template match="node()|@*">
             <xsl:copy>
                 <xsl:apply-templates select="node()|@*"/>
             </xsl:copy>
         </xsl:template>

         <xsl:template match="region/*/*/*
              [deep-equal(.,preceding::*[name()=current()/name()]
                            [@id = current()/@id]
                            [../../@id = current()/../../@id][1])]" />
     </xsl:stylesheet>

the problem with the XSLT right now is that it cannot differentiate
duplicates that happens in siblings (i.e blockA with the same id).

I need to remove a node that are considered as *repetitive*.

**Two node that have the same `name` and `id` will be considered
*repetitive* if it appears one after another and it has the same
`method` and `children`.**

**for example:**

     <elem id="1" method="a" />
     <elem id="1" method="a" />  <!-- this is repetitive for id=1-->
     <elem id="1" method="b" />
     <elem id="1" method="a" />  <!-- this is the new boundary for removal id=1-->
     <elem id="2" method="a" />
     <elem id="1" method="a" />  <!-- this is repetitive for id=1 -->
     <elem id="2" method="a" />  <!-- this is repetitive for id=2 -->

**will be simplified into:**

     <elem id="1" method="a" />
     <elem id="1" method="b" />
     <elem id="1" method="a" />  <!-- this is the new boundary for removal id=1-->
     <elem id="2" method="a" />

  **- Everytime a successive node with the `same id` has `different method`,
    the `boundary` for the next removal for that `id` is reset.**

  - we need to take into account duplicates that are under one parent
or siblings (two or more parents nodes that has the same element name
and id) i.e (in example: `blockX`)
  - if the two nodes being compared did not share the same `gridX`
level, then they should not be considered as duplicates to be removed

Please let me know how to achieve such transformation using XSLT 2.0.
Thanks very much for the help.

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