How can I sort elements by new counted values in their child element. XSLT 1.0

I have an xml sheet of this kind:

<houses>
    <house number="1">
        <mainroom>
            <roomprice>5</roomprice>
            <roomtax>2</roomtax>
        </mainroom>
        <roompricefull>
            <price value="8"/>
        </roompricefull>
    </house>
    <house number="2">
        <mainroom>
            <roomprice>3</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="7"/>
        </roompricefull>
    </house>
    <house number="3">
        <mainroom>
            <roomprice>9</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="4"/>
        </roompricefull>
    </house>
    <house number="4">
        <mainroom>
            <roomprice>12</roomprice>
            <roomtax>3</roomtax>
        </mainroom>
        <roompricefull>
            <price value="6"/>
        </roompricefull>
    </house>
</houses>

so I had to change the value of attribute "value" in "price" element in each of the "house" with the sum of "roomprice" value and "roomtax"

I wrote an xsl transformation of such a kind:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://开发者_运维知识库www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template name="PriceChange" match="price[parent::roompricefull]">
        <xsl:copy>
            <xsl:variable name="sn" select="../../@number"/>
            <xsl:variable name="TaxValue" select="number(//house[@number=string($sn)]/mainroom/roomtax)"/>
            <xsl:variable name="BaseValue" select="number(//house[@number=string($sn)]/mainroom/roomprice)"/>
            <xsl:attribute name="value">
                <xsl:value-of select="string($TaxValue+$BaseValue)"/>
            </xsl:attribute>
            <!--xsl:for-each select="/houses/house">
            <xsl:sort select="houses/house[$sn]/roompricefull/@value"/>
        </xsl:for-each-->
        </xsl:copy> 
    </xsl:template>
</xsl:stylesheet>

But when I started working on sorting "house" elements by my new value, I found problems. I actually don't understand why it's not working, so I commented my last of the dozens examples in up code.

I got this:

<houses>
    <house number="1">
        <mainroom>
            <roomprice>5</roomprice>
            <roomtax>2</roomtax>
        </mainroom>
        <roompricefull>
            <price value="7"/>
        </roompricefull>
    </house>
    <house number="2">
        <mainroom>
            <roomprice>3</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="4"/>
        </roompricefull>
    </house>
    <house number="3">
        <mainroom>
            <roomprice>9</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="10"/>
        </roompricefull>
    </house>
    <house number="4">
        <mainroom>
            <roomprice>12</roomprice>
            <roomtax>3</roomtax>
        </mainroom>
        <roompricefull>
            <price value="15"/>
        </roompricefull>
    </house>
</houses>

But the expected result was:

<houses>
    <house number="4">
        <mainroom>
            <roomprice>12</roomprice>
            <roomtax>3</roomtax>
        </mainroom>
        <roompricefull>
            <price value="15"/>
        </roompricefull>
    </house>   
    <house number="3">
        <mainroom>
            <roomprice>9</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="10"/>
        </roompricefull>
    </house>
    <house number="1">
        <mainroom>
            <roomprice>5</roomprice>
            <roomtax>2</roomtax>
        </mainroom>
        <roompricefull>
            <price value="7"/>
        </roompricefull>
    </house>
    <house number="2">
        <mainroom>
            <roomprice>3</roomprice>
            <roomtax>1</roomtax>
        </mainroom>
        <roompricefull>
            <price value="4"/>
        </roompricefull>
    </house>
</houses>

It would be great if you could help me with sorting and explaining why my example is not working. Seems that I don't understand the meaning of <sort/>, but everything I find tells me just about the usage of it without any explanation. Thank you in advance.

---

it would be great if you could help me with sorting

This is the correct XSLT 1.0 approach.

Notice the correct use of xsl:sort which needs:

• the data-type to be specified, being string the default while we need here number
• the best use of sort inside the xsl:apply-templates
• the application of sorting with the sorting keys of the input document combined as required (sum).

• the sorting order also to be specified being the default ascending

  <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="houses">
     <xsl:copy>
      <xsl:apply-templates select="house">
          <xsl:sort select="mainroom/roomprice + mainroom/roomtax" 
           data-type="number"
           order="descending"/>
      </xsl:apply-templates>
     </xsl:copy>
  </xsl:template>
  
  <xsl:template match="price/@value">
      <xsl:value-of select="
          ../../../mainroom/roomprice 
          + 
          ../../../mainroom/roomtax"/>
  </xsl:template>
  

---

explaining why my example is not working

Your transform does no work mainly because you are trying to sort elements in the wrong context (inside a template matching a deep child in the tree). Moreover:

• you are trying to sort indicating a sorting key by absolute XPath pattern.
• you are not specifying the needed xsl:sort attributes
• you would like final elements be sorted according to a value calculated afterward and not present in the input document. This is not the correct approach. You must always use values present in the input document, eventually combining them properly.

---

Sort by the new price:

<xsl:template match="/">
  <xsl:for-each select="house">
    <xsl:sort select="mainroom/roomprice + mainroom/roomtax"/>
    <xsl:apply-templates select="."/>
  </xsl:for-each>
</xsl:template>

As before:

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

Adjust the price in the output:

<xsl:template match="roompricefull">
  <roompricefull>
    <price value="{../mainroom/roomprice + ../mainroom/roomtax}"/>
  </roompricefull>
</xsl:template>