The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:identity>
<p:with-input>
<doc/>
</p:with-input>
</p:identity>
<p:choose name="choose">
<p:when test="false()">
<p:output port="result" primary="false"/>
<p:identity>
<p:with-input>
<false/>
</p:with-input>
</p:identity>
</p:when>
</p:choose>
<p:wrap-sequence wrapper="result">
<p:with-input pipe="result@choose"/>
</p:wrap-sequence>
</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">Root element is not 'result'.</s:assert>
<s:assert test="count(/result/*)=0">Element 'result' should not have any children.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
