Question

The sample presented is a simplified version of what I am trying to do.

Using XSLT, how do I compare data from nodes in different (non -child) xpaths? I want to compare each cd/artist with the dvd/director to see if they match (see samples below). There are multiple cd’s and dvd’s, but in this simplified example I only used one of each. I tried doing the comparison within one template, but I couldn’t access the dvd xpath. And I couldn’t access the dvd xpath by using a separate template. When using a separate template, I created a ‘compare’ template that I called (<xsl:call-template name="compare">). By access, I mean that I couldn’t print out the dvd/director’s value.

My Question: How do I access one xpath when accessing a different xpath? What I want to do is compare cd artist with dvd director to see if they match. And print out these values, if they match. What I can’t figure out is how to get the artist and director so I can compare them. My xslt does print the cd’s artist value, but I can’t print out the dvd/director’s value.

My samples follows:

The samples come from W3Schools. I modified them to illustrate my question.

Sample XSLT

<xsl:for-each select="catalog/cd">
   <xsl:value-of select="@artist"/>
    <xsl:for-each select="catalog/dvd">         
    <xsl:if test="@director = @artist">
        <xsl:value-of select="@director"/>
    </xsl:if>           
   </xsl:for-each>
 </xsl:for-each>

Sample XML

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>   
<cd title="Unchain my heart" artist="Joe Cocker">

    <country>USA</country>
    <company>EMI</company>
    <price>8.20</price>
    <year>1987</year>
</cd>

    <dvd title="My DVD Movie" director="Joe Cocker">
    <country>USA</country>
    <company>WB</company>
    <price>20.00</price>
    <year>1999</year>
    </dvd>
</catalog>

Thanks for your help in advance.

Answer 1

I think the larger issue is that you’re thinking in procedural terms, which is rarely the right way to approach a problem with XSLT. A better way is to first match cd elements and then select the dvd elements whose director matches the artist. Consider this stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:template match="/*/cd">
        <xsl:value-of select="artist"/>
        <xsl:apply-templates select="../dvd[director=current()/artist]"
            mode="out"/>
    </xsl:template>
    <xsl:template match="dvd" mode="out">
        <xsl:value-of select="director"/>
    </xsl:template>
    <xsl:template match="dvd"/>
</xsl:stylesheet>

The first template applies templates to all dvd elements for which the following predicate evaluates to true: director=current()/artist

Of course, as in your example, we’re just printing the name Joe Cocker twice, which isn’t very useful.

Note: This approach breaks down when there is more than one cd element with the same artist. More complicated grouping strategies would address that case.