Hello, I have to post my question again because the first time I forgot (or I was to stupid) to explain someting.
Thank you very much to Joe and Michael Kay for answering my first question.

Assuming the following xml data:

<shop_articles>
  <article id="1" order="50" show="yes">
    <article_groups>
      <article_group>
        <name>Group1</name>
    <value>value of group1</value>
      </article_group>
      <article_group>
    <name>Quality</name>
    <value>good</value>
      </article_group>
      ...
    </article_groups>

    <article_price>400</article_price>
  </article>

  <article id...
  </article>
</shop_articles>

I am using a <xsl:for-each > instruction to loop through all articles. When I want to sort the articles by the price it works fine with <xsl:sort select="*[name()=$article_sorting]" /> after the <xsl:for-each> instruction when the variable $article_sorting contains the value 'article_price'.

But I don´t know how to set the variable $article_sorting when I want to sort the articles by the <value> of <article_group>´s with the <name>Quality</name>.

Any one have an idea?
Thanks you very much in advance.

Greetings, Wolfgang

<xsl:sort select="*[name()=$article_sorting]" /> allow you to sort by the value any child element, but it doesn't allow you to supply a completely arbitrary sort key at run-time. If you want a completely general solution, consider <xsl:sort select="saxon:evaluate($x)"/> where $x can hold any XPath expression - the trouble is this isn't available in all products.

If you don't want a completely general solution but just one of a number of possible sort keys, you can try multiple sort keys:

<xsl:for-each...
<xsl:sort select="*[name()=$article_sorting]" />
<xsl:sort select="article_groups[$article_sorting='']/article_group[name="Quality"]/value"/>

If $article-sorting is "" the first sort key has no effect, if it is not "" then the second sort key has no effect.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Hi Michael, thank you very much for your help, that was the solution for me. I know now a little bit more of XSL :)
Greetings Wolfgang

That was what I was searching for.
Thank you very much Michael.
Greetings, Wolfgang

Hi Michael, thank you very much again.
That was what I was looking for.
Greetings, Wolfgang