How to select distinct values from XML document using XPATH?

Question

How can I select only distinct elements for the XML document using XPATH?I've tried to use the 'distinct-values' function but it didn't work for some reason..

The XML is similar to the following:

<catalog>

<product>
<size>12</size>
<price>1000</price>
<rating>1</rating>
</product>

<product>
<size>10</size>
<price>1000</price>
<rating>1</rating>
<year>2010</year>
</product>

</catalog>

So what I want to get is the list of distinct children of all the product elements.In the given example it would be - size,price,rating,year My xpath was something like : distinct-values(catalog/product/*)

Answer 1

In XPath 2.0:

distinct-values(/*/*/*/name(.))

In XPath 1.0 this cannot be produced with a single XPath expression.

Using XSLT 1.0:

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

 <xsl:template match="/">
   <xsl:for-each select=
   "/*/*/*[not(../following::*/*
                       [not(name() = name(current()))]
               )
           ]">
     <xsl:value-of select="concat(name(), ' ')"/>
   </xsl:for-each>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the provided XML document, the wanted result is produced:

size price rating year

A more efficient XSLT 1.0 transformation, using keys:

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

 <xsl:key name="kpchildByName"
  match="product/*" use="name()"/>

 <xsl:template match="/">
   <xsl:for-each select=
   "/*/*/*
         [generate-id()
         =
          generate-id(key('kpchildByName', name())[1])
          ]">
     <xsl:value-of select="concat(name(), ' ')"/>
   </xsl:for-each>
 </xsl:template>
</xsl:stylesheet>