The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:viewport match="comment() | processing-instruction()">
<p:with-input>
<p:inline>
<!-- replace here -->
<?target replace-here?>
<doc>
<para>Some para.</para>
</doc>
<?target replace-here?>
<!-- replace here -->
</p:inline>
</p:with-input>
<p:identity>
<p:with-input port="source">
<replaced/>
</p:with-input>
</p:identity>
</p:viewport>
<p:wrap-sequence wrapper="result"/>
</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="result">The document root is not 'result'.</s:assert>
<s:assert test="result/*[1]/name()='replaced'">First child of result is not 'replaced'.</s:assert>
<s:assert test="result/*[2]/name()='replaced'">Second child of result is not 'replaced'.</s:assert>
<s:assert test="result/*[3]/name()='doc'">Third child of result is not 'doc'.</s:assert>
<s:assert test="result/*[4]/name()='replaced'">Fourth child of result is not 'replaced'.</s:assert>
<s:assert test="result/*[5]/name()='replaced'">Fifth child of result is not 'replaced'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
