The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:delete match="processing-instruction()">
<p:with-input>
<p:inline>
<?target content?>
<doc>
<?target content?>
<element>
<?target content?>
<in>
<?target content?>
</in>
</element>
<?target content?>
</doc>
<?target content?>
</p:inline>
</p:with-input>
</p:delete>
</p:declare-step>
Schematron validation
<s:schema xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
<s:pattern>
<s:rule context="/">
<s:assert test="doc">The document root is not 'doc'.</s:assert>
<s:assert test="doc/element">Child of root is not 'element'.</s:assert>
<s:assert test="doc/element/in">'element' does not have a child 'in'.</s:assert>
<s:assert test="count(processing-instruction())=0">There should be no pi at root level.</s:assert>
<s:assert test="count(doc/processing-instruction())=0">There should be no pi as children of doc.</s:assert>
<s:assert test="count(doc/element/processing-instruction())=0">There should be no pi as children of element.</s:assert>
<s:assert test="count(doc/element/in/processing-instruction())=0">There should be no pi as children of in.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
