Say i have the following:
<?xml version="1.0" encoding="utf-8"?>
<rootelement>
<level1 id="id_1" a="1" b="1" c="1" d="1">
  <level2 id="id_2" a="1" b="0" c="0" d="0">
    <contents>Some contents/contents>
  </level2>
  <level2 id="id_3" a="0" b="0" c="0" d="0">
    <contents>Some contents</contents>
  </level2>
</level1>
<level1 id="id_4" a="1" b="1" c="1" d="1">
  <level2 id="id_5" a="1" b="1" c="1" d="1">
    <level3 id="id_6" a="1" b="1" c="1" d="1">
      <contents>Some contents/contents>
    </level3>
    <level3 id="id_7" a="0" b="0" c="0" d="0">
      <contents>Some contents</contents>
    </level3>
  </level2>
</level1>
</rootelement>

Now i want to end up with an XML-document with only those elements which attribute 'a' equals 1, so:

<?xml version="1.0" encoding="utf-8"?>
<rootelement>
<level1 id="id_1">
  <level2 id="id_2">
    <contents>Some contents/contents>
  </level2>
</level1>
<level1 id="id_4">
  <level2 id="id_5">
    <level3 id="id_6">
      <contents>Some contents/contents>
    </level3>
  </level2>
</level1>
</rootelement>

I have made several attempts, but i always end up with either too much or too less information in the resultdocument.
Note: I don't know how much 'levels' the document has!

Any help is greatly appreciated!
Regards, Raoul.

No-one can tell you where you're going wrong unless you show your code!



Michael Kay
http://www.saxonica.com/

All right, here is my stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

  <xsl:output method="xml" encoding="utf-8" />

  <xsl:template match="/">
    <xsl:element name="rootdocument">
      <xsl:apply-templates select="*" />
    </xsl:element>
  </xsl:template>

  <xsl:template match="*">
    <xsl:choose>
      <xsl:when test="name() = 'contents'">
        <xsl:if test="../@a = '1'">
          <xsl:copy-of select="." />
        </xsl:if>
      </xsl:when>
      <xsl:when test="starts-with(name(), 'level')">
        <xsl:if test="@a = '1'">
          <xsl:element name="{name()}" use-attribute-sets="Item">

          </xsl:element>
        </xsl:if>
      </xsl:when>
      <xsl:otherwise />
    </xsl:choose>
    <xsl:apply-templates />
  </xsl:template>

  <xsl:attribute-set name="Item">
    <xsl:attribute name="id">
      <xsl:value-of select="@id" />
    </xsl:attribute>
  </xsl:attribute-set>

</xsl:stylesheet>

Quick fix:
Uncomment the inside your <xsl:when test="starts-with(name(), 'level')"> block, otherwise the elements won't nest at all.

Move the <xsl:apply-templates /> after the <xsl:choice>, inside, to the <xsl:otherwise> I suppose.
---
Smarter more durable fix: when you call apply-templates, only select the ones you want, eg.
<xsl:apply-templates select="*[(@a = '1') or not (@a)]/>

Thank you very much, it works just perfectly.