XSLT - Why are multiple nodes getting merged in the output ( Group By)

Question

All- I am trying to understand the root cause for 2 nodes getting merged.

The input XML

<?xml version='1.0' encoding='UTF-8'?>
<Employees>
    <Employee>
        <Employee_ID>E00001</Employee_ID>
        <Legal_Name Descriptor="John Doe" />         
        <lastName>Doe</lastName>
        <firstName>John</firstName>
        <P_From_Date>2015-04-01-08:00</P_From_Date>
        <P_End_Date>2015-12-31-08:00</P_End_Date>

        <Transaction>            
            <Plan Descriptor="Plan A" />            
            <effective_date>2015-03-22-08:00</effective_date>
                    <end_date>2015-10-22</end_date>
            <Annual_Cost>6000</Annual_Cost>
        </Transaction>

        <Transaction>            
            <Plan Descriptor="Plan A" />            
            <effective_date>2015-02-03-08:00</effective_date>
            <Annual_Cost>4000</Annual_Cost>
        </Transaction>

        <Transaction>            
            <Plan Descriptor="Plan A" />            
            <effective_date>2013-02-03-08:00</effective_date>
            <Annual_Cost>3000</Annual_Cost>
        </Transaction>


        <Transaction>            
            <Plan Descriptor="Plan B" />            
            <effective_date>2014-12-03-08:00</effective_date>
            <Annual_Cost>12000</Annual_Cost>
        </Transaction>  

        <Transaction>            
            <Plan Descriptor="Plan B" />            
            <effective_date>2014-10-03-08:00</effective_date>
            <Annual_Cost>1000</Annual_Cost>
        </Transaction>  

   </Employee>       

     <Employee>
        <Employee_ID>E00002</Employee_ID>
        <Legal_Name Descriptor="John Doe" />         
        <lastName>Test</lastName>
        <firstName>Jane</firstName>
        <P_From_Date>2015-01-01-08:00</P_From_Date>

        <Transaction>            
            <Plan Descriptor="Plan D" />            
            <effective_date>2015-05-22-08:00</effective_date>
            <Annual_Cost>12000</Annual_Cost>
        </Transaction>

        <Transaction>            
            <Plan Descriptor="Plan D" />            
            <effective_date>2014-03-01-08:00</effective_date>
            <Annual_Cost>9000</Annual_Cost>
        </Transaction>

        <Transaction>            
            <Plan Descriptor="Plan C" />            
            <effective_date>2014-12-03-08:00</effective_date>
            <Annual_Cost>3000</Annual_Cost>
        </Transaction>


        <Transaction>            
            <Plan Descriptor="Plan C" />            
            <effective_date>2013-01-03-08:00</effective_date>
            <Annual_Cost>3000</Annual_Cost>
        </Transaction>


     </Employee>     
</Employees>

And the XSLT

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"

    xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml"/>
    <!-- TODO customize transformation rules 
         syntax recommendation http://www.w3.org/TR/xslt 
    -->
    <xsl:variable name="newline" select="'&#xd;'"/>
    <xsl:variable name="delimiter">,</xsl:variable>
    <xsl:variable name="qualifier">
        <xsl:text>"</xsl:text>
    </xsl:variable>

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

    <xsl:template match="Employee">

        <EE>

        <EID>
        <xsl:value-of select="Employee_ID" />
        </EID>        

        <FULNAME>
        <xsl:value-of select="Legal_Name/@Descriptor"/>
        </FULNAME>
        <LNAME>
        <xsl:value-of select="lastName"/>
        </LNAME>        
        <FNAME>
        <xsl:value-of select="firstName"/>
        </FNAME>


        <xsl:variable name="bework">
            <xsl:for-each-group select="Transaction" group-by="Plan/@Descriptor" >
                <berow>
                    <CurrentGroup>
                        <xsl:value-of select="current-grouping-key()"/>
                    </CurrentGroup>
                    <parm_from_date><xsl:value-of select="../P_From_Date" /></parm_from_date>
                    <xsl:for-each select="current-group()">
                        <begin-date><xsl:copy-of select="effective_date" /></begin-date>

                        <include-flag >
                            <xsl:choose>
                                <xsl:when test="xs:date( substring(effective_date,1,10)) &gt;=  xs:date(substring(../P_From_Date,1,10))">
                                    <xsl:text>Y</xsl:text>
                                </xsl:when>
                                <xsl:otherwise>
                                    <xsl:text>N</xsl:text>
                                </xsl:otherwise>
                            </xsl:choose>

                        </include-flag>
                        <adj-begin-date>
                            <xsl:choose>
                                <xsl:when test="xs:date(effective_date) &gt;= xs:date(../P_From_Date_1) ">
                                    <xsl:value-of select="effective_date"/>
                                </xsl:when>
                                <xsl:otherwise>
                                    <xsl:value-of select="../P_From_Date_1"/>
                                </xsl:otherwise>
                             </xsl:choose>
                        </adj-begin-date>
                        <end_date>
                            <xsl:value-of select="current-group()/end_date"/>
                        </end_date>
                        <Cost>
                            <xsl:value-of select="Annual_Cost"/>
                        </Cost>
                    </xsl:for-each>
                </berow>
            </xsl:for-each-group>
        </xsl:variable>

        <xsl:for-each select="$bework/berow">


            <CGR>
            <xsl:value-of select="CurrentGroup" />
            </CGR>



            <PFRMDT>            
            <xsl:value-of select="parm_from_date" />
            </PFRMDT>


            <BDT>
            <xsl:value-of select="begin-date" />
            </BDT>


            <FLAG>
            <xsl:value-of select="include-flag" />
            </FLAG>


            <ADJBGNDT>
            <xsl:value-of select="$qualifier"/>
            </ADJBGNDT>


            <EDATE>            
            <xsl:value-of select="$qualifier"/>
            </EDATE>

            <CO>
            <xsl:value-of select="Cost" />                        
            </CO>


        </xsl:for-each>

        </EE>
    </xsl:template>
</xsl:stylesheet>

The result

<?xml version="1.0" encoding="UTF-8"?>
<EES xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <EE>
        <EID>E00001</EID>
        <FULNAME>John Doe</FULNAME>
        <LNAME>Doe</LNAME>
        <FNAME>John</FNAME>
        <CGR>Plan A</CGR>
        <PFRMDT>2015-04-01-08:00</PFRMDT>
        <BDT>2015-03-22-08:00 2015-02-03-08:00 2013-02-03-08:00</BDT>
        <FLAG>N N N</FLAG>
        <ADJBGNDT>"</ADJBGNDT>
        <EDATE>"</EDATE>
        <CO>6000 4000 3000</CO>
        <CGR>Plan B</CGR>
        <PFRMDT>2015-04-01-08:00</PFRMDT>
        <BDT>2014-12-03-08:00 2014-10-03-08:00</BDT>
        <FLAG>N N</FLAG>
        <ADJBGNDT>"</ADJBGNDT>
        <EDATE>"</EDATE>
        <CO>12000 1000</CO>
    </EE>        

    <EE>
        <EID>E00002</EID>
        <FULNAME>John Doe</FULNAME>
        <LNAME>Test</LNAME>
        <FNAME>Jane</FNAME>
        <CGR>Plan D</CGR>
        <PFRMDT>2015-01-01-08:00</PFRMDT>
        <BDT>2015-05-22-08:00 2014-03-01-08:00</BDT>
        <FLAG>Y N</FLAG>
        <ADJBGNDT>"</ADJBGNDT>
        <EDATE>"</EDATE>
        <CO>12000 9000</CO>
        <CGR>Plan C</CGR>
        <PFRMDT>2015-01-01-08:00</PFRMDT>
        <BDT>2014-12-03-08:00 2013-01-03-08:00</BDT>
        <FLAG>N N</FLAG>
        <ADJBGNDT>"</ADJBGNDT>
        <EDATE>"</EDATE>
        <CO>3000 3000</CO>
    </EE>    
</EES>

If you look at John Doe's BDT node, there are 2 dates. These are 2 nodes for the sample plan are getting added to the same node despite looping through the current group.

WHat is causing this? And what should be done to remedy this? I will have to use variables as there is more manulations I will have to do. But that is for another day.

Thanks for providng me some insight.

Answer 1

Perhaps you just need to change:

<BDT>
<xsl:value-of select="begin-date" />
</BDT>

to:

<BDT>
<xsl:copy-of select="begin-date" />
</BDT>

In XSLT 2.0, xsl:value-of will generate a single text node, concatenating the values of all matching nodes, separated by a space (or another separator, if specified).

---

Additional explanation:

WHat is causing this?

The reason why your nodes are getting merged into a single text node is that you are using xsl:value-of when you try to fetch them from the $bework variable in order to write them into the output tree.

Consider the following simplified example:

XML

<root>
    <item>
        <category>A</category>
        <amount>1000</amount>
    </item>
    <item>
        <category>A</category>
        <amount>500</amount>
    </item>
    <item>
        <category>A</category>
        <amount>250</amount>
    </item>
    <item>
        <category>B</category>
        <amount>600</amount>
    </item>
    <item>
        <category>B</category>
        <amount>300</amount>
    </item>
</root>

XSLT 2.0

<xsl:stylesheet version="2.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:strip-space elements="*"/>

<xsl:template match="/root">
    <xsl:variable name="groups">
        <xsl:for-each-group select="item" group-by="category">
            <group category="{current-grouping-key()}">
                <xsl:for-each select="current-group()">
                    <amount>
                        <xsl:value-of select="amount"/>
                    </amount>
                </xsl:for-each>
            </group>
        </xsl:for-each-group>
    </xsl:variable>
    <output>    
        <xsl:for-each select="$groups/group">
            <group category="{@category}">
                <copy-of-amount>    
                    <xsl:copy-of select="amount"/>
                </copy-of-amount>       
                <for-each-amount>   
                    <xsl:for-each select="amount">
                        <new-node value="{.}"/>
                    </xsl:for-each>
                </for-each-amount>      
                <sum-of-amount> 
                    <xsl:value-of select="sum(amount)"/>
                </sum-of-amount>        
                <value-of-amount>   
                    <xsl:value-of select="amount"/>
                </value-of-amount>      
            </group>
        </xsl:for-each>
    </output>       
</xsl:template>

</xsl:stylesheet>

Result

<?xml version="1.0" encoding="UTF-8"?>
<output>
   <group category="A">
      <copy-of-amount>
         <amount>1000</amount>
         <amount>500</amount>
         <amount>250</amount>
      </copy-of-amount>
      <for-each-amount>
         <new-node value="1000"/>
         <new-node value="500"/>
         <new-node value="250"/>
      </for-each-amount>
      <sum-of-amount>1750</sum-of-amount>
      <value-of-amount>1000 500 250</value-of-amount>
   </group>
   <group category="B">
      <copy-of-amount>
         <amount>600</amount>
         <amount>300</amount>
      </copy-of-amount>
      <for-each-amount>
         <new-node value="600"/>
         <new-node value="300"/>
      </for-each-amount>
      <sum-of-amount>900</sum-of-amount>
      <value-of-amount>600 300</value-of-amount>
   </group>
</output>

As you can see, inside the $myVar variable, each group contains 2-3 distinct amount nodes. You can copy them, sum them or create something for each one of them. However, when you do:

<xsl:value-of select="amount"/>

you are addressing all the amount nodes in the current group, and you will get a result that incorporates them all, same as:

<xsl:value-of select="sum(amount)"/>

returns a result based on all the amount nodes being addressed.

And what should be done to remedy this?

We won't know that until you tell us what is the actual result you want to get. In the comments below you said that:

the final result is really the total cost per employee.

If so, the example above shows how to get it.

Answer 2

Inside of your bework variable you create a berow element for each Transaction group but then you use <xsl:for-each select="current-group()"> to output a begin-date for each Transaction in that group, without structuring or wrapping them further. With your input that means that berow element can contain two or three begin-date elements.

Then you have <xsl:for-each select="$bework/berow"> and inside

        <BDT>
        <xsl:value-of select="begin-date" />
        </BDT>

which will select and output the string value of the two or three begin-date elements.

I am not sure which value you want to output for BDT, you could use e.g. <xsl:value-of select="begin-date[1]"/> or <xsl:value-of select="begin-date[last()]"/> to output only the string value of the first or last element created earlier.