Question

I am trying to select all the <set>erase</set> elements such that if two or more elements have the <set>erase</set> in hierarchy (Ex: <b> and <d> both have <set>erase</set>) then only the element in parent node name has to be selected(ie <b> in this case).

Sample xml below:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<a>
    <b>
        <set>erase</set>
        <d>
            <set>erase</set>
        </d>
    </b>

    <c>
        <x></x>
    </c>

    <e>
        <y>
            <set>erase</set>
            <q></q>
        </y>
        <z>
            <p>
                <set>erase</set>
            </p>
        </z>
    </e>
</a>

When I use the query = //set[contains(.,'erase')] I get all <set>erase</set> of nodesList b,d,y,p in result set.

I need help in framing the query to select <set>erase</set> of b , y and p.

Answer 1

Here is the same solution:

One XPath expression that selects exactly the wanted elements is:

          //*[set[. = 'erase' and not(node()[2])]
             and
              not(ancestor::*
                     [set
                        [. = 'erase' and not(node()[2])]
                     ]
                  )
              ]

XSLT – based verification:

<xsl:stylesheet version="1.0"
         xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
         <xsl:output omit-xml-declaration="yes" indent="yes"/>
         <xsl:strip-space elements="*"/>

         <xsl:template match="/">
             <xsl:for-each select=
             "//*[set[. = 'erase' and not(node()[2])]
                 and
                  not(ancestor::*
                         [set
                            [. = 'erase' and not(node()[2])]
                         ]
                      )
                  ]">

              <xsl:value-of select="name()"/>
              <xsl:text>&#xA;</xsl:text>
            </xsl:for-each>
         </xsl:template>
</xsl:stylesheet>

when this transformation is applied on the provided XML document:

<a>
    <b>
        <set>erase</set>
        <d>
            <set>erase</set>
        </d>
    </b>
    <c>
        <x></x>
    </c>
    <e>
        <y>
            <set>erase</set>
            <q></q>
        </y>
        <z>
            <p>
                <set>erase</set>
            </p>
        </z>
    </e>
</a>

The contained XPath expression is evaluated and the names of the selected elements are output — correctly and as expected:

b
y
p

If you need to select the set children of the selected above elements, just append the above XPath expression with /set:

          //*[set[. = 'erase' and not(node()[2])]
             and
              not(ancestor::*
                     [set
                        [. = 'erase' and not(node()[2])]
                     ]
                  )
              ]
               /set

Again, XSLT – based verification:

<xsl:stylesheet version="1.0"
         xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
         <xsl:output omit-xml-declaration="yes" indent="yes"/>
         <xsl:strip-space elements="*"/>

         <xsl:template match="/">
             <xsl:copy-of select=
             "//*[set[. = 'erase' and not(node()[2])]
                 and
                  not(ancestor::*
                         [set
                            [. = 'erase' and not(node()[2])]
                         ]
                      )
                  ]
                   /set
                  "/>
         </xsl:template>
</xsl:stylesheet>

This transformation just evaluates the above XPath expression and copies to the output the correctly selected three set elements:

<set>erase</set>
<set>erase</set>
<set>erase</set>