Question

I’m trying to merge two file that have the same structure, and some data in common. So if a node has the same name in both files, a new node should be created with the children of both original nodes. The original files are the following:

file1.xml
<?xml version='1.0' encoding='UTF-8'?>
<BROADRIDGE>
    <SECURITY CUSIP='CUSIP1' DESCRIPT='CUSIP1'>
        <CUSTOMER ID='M1'/>
        <CUSTOMER ID='M2'/>
        <CUSTOMER ID='M3'/>
    </SECURITY>
    <SECURITY CUSIP='CUSIP3' DESCRIPT='CUSIP3'>
        <CUSTOMER ID='M4'/>
        <CUSTOMER ID='M5'/>
        <CUSTOMER ID='M6'/>
    </SECURITY>
</BROADRIDGE>

file2.xml
<?xml version='1.0' encoding='UTF-8'?>
<BROADRIDGE>
    <SECURITY CUSIP='CUSIP1' DESCRIPT='CUSIP1'>
        <CUSTOMER ID='B1'/>
        <CUSTOMER ID='B2'/>
        <CUSTOMER ID='B3'/>
    </SECURITY>
    <SECURITY CUSIP='CUSIP2' DESCRIPT='CUSIP2'>
        <CUSTOMER ID='B4'/>
        <CUSTOMER ID='B5'/>
        <CUSTOMER ID='B6'/>
    </SECURITY>
</BROADRIDGE>

The idea is to create a new XML file with the same structure that contains the information from both files, merging those SECURITY nodes that have the same CUSIP attribute. In this case the result should be the following:

<?xml version="1.0" encoding="UTF-8"?>
<BROADRIDGE>
    <SECURITY CUSIP="CUSIP1">
        <CUSTOMER ID="M1"/>
        <CUSTOMER ID="M2"/>
        <CUSTOMER ID="M3"/>
        <CUSTOMER ID='B1'/>
        <CUSTOMER ID='B2'/>
        <CUSTOMER ID='B3'/>
    </SECURITY>
    <SECURITY CUSIP="CUSIP3">
        <CUSTOMER ID="M4"/>
        <CUSTOMER ID="M5"/>
        <CUSTOMER ID="M6"/>
    </SECURITY>
    <SECURITY CUSIP="CUSIP2">
        <CUSTOMER ID="B4"/>
        <CUSTOMER ID="B5"/>
        <CUSTOMER ID="B6"/>
    </SECURITY>
</BROADRIDGE>

I’ve defined the folling xml to joing them:

<?xml version="1.0"?>                                  
<MASTERFILE>
   <FILE>\file1.xml</FILE>
   <FILE>\file2.xml</FILE>
</MASTERFILE>

And the following XSL to do the merge:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/MASTERFILE">
        <BROADRIDGE>
            <xsl:variable name="securities" select="document(FILE)/BROADRIDGE/SECURITY"/>
            <xsl:for-each select="$securities">
                <xsl:if test="generate-id(.) = generate-id($securities[@CUSIP=current()/@CUSIP])">
                    <SECURITY>
                        <xsl:attribute name="CUSIP" ><xsl:value-of select="@CUSIP"/></xsl:attribute>
                        <xsl:for-each select="CUSTOMER">
                            <CUSTOMER>
                                <xsl:attribute name="ID" ><xsl:value-of select="@ID"/></xsl:attribute>
                            </CUSTOMER>
                        </xsl:for-each>
                    </SECURITY>
                </xsl:if>
            </xsl:for-each>
        </BROADRIDGE>
    </xsl:template>
</xsl:stylesheet>

But I’m getting the following:

<?xml version="1.0" encoding="UTF-8"?>
<BROADRIDGE>
    <SECURITY CUSIP="CUSIP1">
        <CUSTOMER ID="M1"/>
        <CUSTOMER ID="M2"/>
        <CUSTOMER ID="M3"/>
    </SECURITY>
    <SECURITY CUSIP="CUSIP3">
        <CUSTOMER ID="M4"/>
        <CUSTOMER ID="M5"/>
        <CUSTOMER ID="M6"/>
    </SECURITY>
    <SECURITY CUSIP="CUSIP2">
        <CUSTOMER ID="B4"/>
        <CUSTOMER ID="B5"/>
        <CUSTOMER ID="B6"/>
    </SECURITY>
</BROADRIDGE>

Any idea why it’s not merging the CUSTOMERS from both file for SECURITY with CUSIP =
CUSIP1?

Answer 1

(See my comment on the “one-way-merge” on the OP.) Here’s my (very inefficient) solution to the merge problem:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:variable name="set1" select="document('file1.xml')/BROADRIDGE/SECURITY"/>
    <xsl:variable name="set2" select="document('file2.xml')/BROADRIDGE/SECURITY"/>

    <xsl:template match="/">
        <BROADRIDGE>
            <!-- walk over all relevant nodes -->
            <xsl:for-each select="$set1 | $set2">
                <xsl:variable name="position" select="position()"/>
                <xsl:variable name="cusip" select="@CUSIP"/>
                <!-- if we see this CUSIP for the first time, --> 
                <xsl:if test="count($nodes[position() &lt; $position][@CUSIP = $cusip])=0">
                    <SECURITY>                            
                        <xsl:attribute name="CUSIP"><xsl:value-of select="$cusip"/></xsl:attribute>
                        <!-- copy nodes from both sets with matching attribute -->
                        <xsl:copy-of select="$set1[@CUSIP = $cusip]/*"/>
                        <xsl:copy-of select="$set2[@CUSIP = $cusip]/*"/>
                    </SECURITY>
                </xsl:if>
            </xsl:for-each>
        </BROADRIDGE>
    </xsl:template>
</xsl:stylesheet>

Note that the stylesheet does not suppose any particular document – it simply loads the two files as variables. One can improve th xslt design by parameterizing the urls for the to be loaded XML documents

To apply the merge to multiple documents, you can create a file, say master.xml that lists all the files to process like this:

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="merge.xslt"?>
<files>
  <file>file1.xml</file>
  <file>file2.xml</file>
  ...
  <file>fileN.xml</file>    
</files>

In file1.xml, I have this:

<?xml version='1.0' encoding='UTF-8'?>
<BROADRIDGE>
  <SECURITY CUSIP='CUSIP1' DESCRIPT='CUSIP1'>
    <CUSTOMER ID='M1'/>
    <CUSTOMER ID='M2'/>
    <CUSTOMER ID='M3'/>
  </SECURITY>
  <SECURITY CUSIP='CUSIP3' DESCRIPT='CUSIP3'>
    <CUSTOMER ID='M4'/>
    <CUSTOMER ID='M5'/>
    <CUSTOMER ID='M6'/>
  </SECURITY>
</BROADRIDGE>

In file2.xml, I have this:

<?xml version='1.0' encoding='UTF-8'?>
<BROADRIDGE>
  <SECURITY CUSIP='CUSIP1' DESCRIPT='CUSIP1'>
    <CUSTOMER ID='B1'/>
    <CUSTOMER ID='B2'/>
    <CUSTOMER ID='B3'/>
  </SECURITY>
  <SECURITY CUSIP='CUSIP2' DESCRIPT='CUSIP2'>
    <CUSTOMER ID='B4'/>
    <CUSTOMER ID='B5'/>
    <CUSTOMER ID='B6'/>
  </SECURITY>
</BROADRIDGE>

the merge.xslt is a modified version of the earlier one, which is now capable of processing a variable number of files (the files listed in master.xml):

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
  <xsl:call-template name="merge-files"/>
</xsl:template>

<!-- loop through file names, load documents -->
<xsl:template name="merge-files">
  <xsl:param name="files" select="/files/file/text()"/>
  <xsl:param name="num-files" select="count($files)"/>
  <xsl:param name="curr-file" select="0"/>
  <xsl:param name="set" select="/*[0]"/>
  <xsl:choose> <!-- if we still have files, concat them to $set -->
    <xsl:when test="$curr-file &lt; $num-files">
      <xsl:call-template name="merge-files">
        <xsl:with-param name="files" select="$files"/>
        <xsl:with-param name="num-files" select="$num-files"/>
        <xsl:with-param name="curr-file" select="$curr-file + 1"/>
        <xsl:with-param name="set" select="$set | document($files[$curr-file+1])/BROADRIDGE/SECURITY"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise> <!-- no more files, start merging. -->
      <xsl:call-template name="merge">
        <xsl:with-param name="nodes" select="$set"/>
      </xsl:call-template>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>

<!-- perform the actual merge -->
<xsl:template name="merge">
  <xsl:param name="nodes"/>
  <BROADRIDGE>
    <xsl:for-each select="$nodes"> <!-- look at all possible nodes to merge -->
      <xsl:variable name="position" select="position()"/>
      <xsl:variable name="cusip" select="@CUSIP"/>

      <!-- when we encounter this id for the 1st time -->
      <xsl:if test="count($nodes[position() &lt; $position][@CUSIP = $cusip])=0"> 
        <SECURITY>
          <xsl:attribute name="CUSIP"><xsl:value-of select="$cusip"/></xsl:attribute>
          <!-- copy all node data related to this cusip here -->
          <xsl:for-each select="$nodes[@CUSIP = $cusip]">
            <xsl:copy-of select="*"/>
          </xsl:for-each>
        </SECURITY>
      </xsl:if>
    </xsl:for-each>
  </BROADRIDGE>
</xsl:template>

</xsl:stylesheet>

Running this gives me this output:

<BROADRIDGE>
  <SECURITY CUSIP="CUSIP1">
    <CUSTOMER ID="M1"/>
    <CUSTOMER ID="M2"/>
    <CUSTOMER ID="M3"/>
    <CUSTOMER ID="B1"/>
    <CUSTOMER ID="B2"/>
    <CUSTOMER ID="B3"/>
  </SECURITY>
  <SECURITY CUSIP="CUSIP3">
    <CUSTOMER ID="M4"/>
    <CUSTOMER ID="M5"/>
    <CUSTOMER ID="M6"/>
  </SECURITY>
  <SECURITY CUSIP="CUSIP2">
    <CUSTOMER ID="B4"/>
    <CUSTOMER ID="B5"/>
    <CUSTOMER ID="B6"/>
  </SECURITY>
</BROADRIDGE>