The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" name="pipeline" version="3.0">
<p:output port="result"/>
<p:try name="try">
<p:identity>
<p:with-input>
<initial/>
</p:with-input>
</p:identity>
<p:catch>
<p:identity>
<p:with-input>
<catch/>
</p:with-input>
</p:identity>
</p:catch>
<p:finally>
<p:output port="finally" primary="false" pipe="@producer"/>
<p:wrap-sequence wrapper="wrapper" name="producer"/>
</p:finally>
</p:try>
<p:identity>
<p:with-input pipe="finally"/>
</p:identity>
</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="wrapper">The document root is not 'wrapper'.</s:assert>
<s:assert test="empty(wrapper/*)">Element 'wrapper' should not have children.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
