The pipeline
<p:declare-step xmlns:c="http://www.w3.org/ns/xproc-step" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:try name="try">
<p:error code="error">
<p:with-input>
<doc>
<value>../documents/ab-doc2.xml</value>
</doc>
</p:with-input>
</p:error>
<p:catch>
<p:identity>
<p:with-input>
<irrelevant/>
</p:with-input>
</p:identity>
</p:catch>
<p:finally>
<p:output port="finally" primary="false" pipe="@producer"/>
<p:identity name="producer">
<p:with-input href="{/c:errors/c:error/doc/value/text()}"/>
</p:identity>
</p:finally>
</p:try>
<p:identity>
<p:with-input pipe="finally@try"/>
</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="/doc">Document root is not named 'doc'.</s:assert>
<s:assert test="/doc/@att='1'">Attribute 'att' does not have value '1'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
