The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:choose name="choose">
<p:when test="true()">
<p:output port="result" primary="true"/>
<p:output port="when-output">
<when/>
</p:output>
<p:identity>
<p:with-input>
<true/>
</p:with-input>
</p:identity>
</p:when>
<p:otherwise>
<p:output port="result" primary="true"/>
<p:output port="otherwise-output">
<otherwise/>
</p:output>
<p:identity>
<p:with-input>
<false/>
</p:with-input>
</p:identity>
</p:otherwise>
</p:choose>
<p:wrap-sequence name="wrap1" wrapper="when">
<p:with-input pipe="when-output@choose"/>
</p:wrap-sequence>
<p:wrap-sequence name="wrap2" wrapper="otherwise">
<p:with-input pipe="otherwise-output@choose"/>
</p:wrap-sequence>
<p:wrap-sequence wrapper="result">
<p:with-input pipe="@choose @wrap1 @wrap2"/>
</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="/result/*[1]/name()='true'">The first child of result is not named 'true'.</s:assert>
<s:assert test="/result/*[2]/name()='when'">The second child of result is not named 'when'.</s:assert>
<s:assert test="/result/when/when">'when' does not have a child 'when'.</s:assert>
<s:assert test="/result/*[3]/name()='otherwise'">The third child of result is not named 'otherwise'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
