xsl sorting on an an average value of 3 child elements

I have the following xml. What I want to do with my XSL is sort the output on the total value of the elements productDesignRating, productPriceRating and productPerfromanceRating. So far no luck in trying to get this done. Any help will be appreciated i need to be able to do this in xsl 1 so no xsl2 functions.

    <DocumentElement xmlns="DotNetNuke/UserDefinedTable">
  <QueryResults>
    <productCategory>cat1</productCategory>
    <productTitle>product1</productTitle>
    <productImage>&lt;img alt="productImage" title="productImage" src="/skinconversion/Portals/12/babynokiko.jpg" /&gt;</productImage>
    <productDesignRating>3</productDesignRating>
    <productPriceRating>4</productPriceRating>
    <productPerformanceRating>4</productPerformanceRating>
    <productPrice>10</productPrice>
    <productSummary>description</productSummary>
    <productUrl>http://www.2dnn.com</productUrl>
  </QueryResults>
  <QueryResults>
    <productCategory>cat2</productCategory>
    <productTitle>product2</productTitle>
    <productImage>&lt;img alt="productImage" title="productImage" src="/skinconversion/Portals/12/babynokiko.jpg" /&gt;</productImage>
    <productDesignRating>3</productDesignRating>
    <productPriceRating>3</productPriceRating>
    <productPerformanceRating>3</productPerformanceRating>
    <productPrice>10</productPrice>
    <productSummary>description</productSummary>
    <productUrl>http://www.2dnn.com</productUrl>
  </QueryResults>
  <QueryResults>
    <productCategory>cat3</productCategory>
    <productTitle>product3</productTitle>
    <productImage>开发者_StackOverflow社区&lt;img alt="productImage" title="productImage" src="/skinconversion/Portals/12/babynokiko.jpg" /&gt;</productImage>
    <productDesignRating>1</productDesignRating>
    <productPriceRating>2</productPriceRating>
    <productPerformanceRating>3</productPerformanceRating>
    <productPrice>56</productPrice>
    <productSummary>description</productSummary>
    <productUrl>http://www.2dnn.com</productUrl>
  </QueryResults>
</DocumentElement>

Try this:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:my="DotNetNuke/UserDefinedTable">
    <xsl:template match="node()">
        <xsl:copy>
            <xsl:apply-templates select="node()">
                <xsl:sort select="my:productDesignRating +  
                                  my:productPriceRating +  
                                  my:productPerformanceRating"
                    data-type="number"/>
            </xsl:apply-templates>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

This is just a simplified identity template (not processing any attributes), but applying a numerical sort on the sum of the values of the 3 specified child elements – if they are present.

Specifically note the use of the data-type attribute, allowing to specify that the sorting base should be numbers, so the order here is 6,9,11 (for strings, which is default, it would be 11,6,9)…

[To reverse the order, simply add the order="descending" attribute]