Question

If I have an XML node that looks like this

<node name="a">
  <element ref="bb" />
  <element ref="cc" />
  <element ref="prefix_dd" />
  <element ref="prefix_ee" />
</node>

I’d like to write an XSLT to return

<node name="a">
  <element ref="prefix_dd" />
  <element ref="prefix_ee" />
</node>

Answer 1

Probably one of the shortest such transformations:

<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="node()[not(@ref[not(starts-with(.,'prefix_'))])]|@*">
     <xsl:copy>
       <xsl:apply-templates select="node()|@*"/>
     </xsl:copy>
 </xsl:template>
</xsl:stylesheet>

When applied on the provided XML document:

<node name="a">
    <element ref="bb" />
    <element ref="cc" />
    <element ref="prefix_dd" />
    <element ref="prefix_ee" />
</node>

the wanted, correct result is produced:

<node name="a">
   <element ref="prefix_dd"/>
   <element ref="prefix_ee"/>
</node>

Explanation: Modified identity rule.