You can do it (albeit inefficiently) like this:

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

<xsl:template match="v">
  <xsl:text>X Y Z
</xsl:text>
  <xsl:for-each select="w">
    <xsl:sort select="x"/>
    <xsl:sort select="y"/>
    <xsl:sort select="z"/>
    <xsl:choose>
      <xsl:when test="position()=1">
	<xsl:value-of select="x"/>
      </xsl:when>
      <xsl:otherwise>
	<xsl:variable name="pos" expr="position()"/>
	<xsl:variable name="x" expr="x"/>
	<xsl:for-each select="../w">
	  <xsl:sort select="x"/>
	  <xsl:sort select="y"/>
	  <xsl:sort select="z"/>
	  <xsl:if test="position() = $pos - 1">
	     <xsl:choose>
	       <xsl:when test="not(x=$x)">
		 <xsl:value-of select="$x"/>
	       </xsl:when>
	       <xsl:otherwise><xsl:text> </xsl:text></xsl:otherwise>
	     </xsl:choose>
	  </xsl:if>
	</xsl:for-each>
      </xsl:otherwise>
    </xsl:choose> 
    <xsl:text> </xsl:text>
    <xsl:value-of select="y"/>
    <xsl:text> </xsl:text>
    <xsl:value-of select="z"/>
    <xsl:text>&#xA;</xsl:text>
  </xsl:for-each>
</xsl:template>

</xsl:stylesheet>

"G. Ken Holman" wrote:
> 
> Hi all,
> 
> XSLT 19990421 is considered "feature complete", yet I've come across what I
> think may represent the need for a frequently-used facility I cannot find
> in the working draft.
> 
> I'm hoping someone on the list can show me if the following problem can,
> indeed, be solved with Working Draft 19990421, because I've tried a lot of
> things and keep getting caught up in the prewired document order of the axes.
> 
> First, here is a problem that I think will be a frequent need that I was
> able to solve in a straightforward fashion, that of suppressing redundant
> entries in a table:
> 
> From:
> 
> <?xml version="1.0"?>
> <v>
> <w><x>1</x><y>1</y><z>a</z></w>
> <w><x>1</x><y>2</y><z>b</z></w>
> <w><x>1</x><y>3</y><z>c</z></w>
> <w><x>2</x><y>1</y><z>d</z></w>
> <w><x>2</x><y>2</y><z>e</z></w>
> <w><x>3</x><y>1</y><z>f</z></w>
> </v>
> 
> Produce:
> 
>  X   Y   Z
>  1   1   a
>      2   b
>      3   c
>  2   1   d
>      2   e
>  3   1   f
> 
> ..... suppressing redundant values for X.

> Now, consider the problem where I want the same output from an unsorted
> collection:
> 
> <?xml version="1.0"?>
> <v>
> <w><x>1</x><y>2</y><z>b</z></w>
> <w><x>3</x><y>1</y><z>f</z></w>
> <w><x>1</x><y>3</y><z>c</z></w>
> <w><x>2</x><y>2</y><z>e</z></w>
> <w><x>2</x><y>1</y><z>d</z></w>
> <w><x>1</x><y>1</y><z>a</z></w>
> </v>

> So, my question is, can this problem be solved with the proposed working
> draft in a single pass, and if not, is it important enough a problem that
> it should be solved with version 1.0?



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