The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:insert match="/doc" position="first-child">
<p:with-input>
<p:inline document-properties="map{'prop':'value'}">
<doc/>
</p:inline>
</p:with-input>
<p:with-input port="insertion">
<a/>
</p:with-input>
</p:insert>
<p:identity>
<p:with-input>
<result>{p:document-property(.,'prop')}</result>
</p:with-input>
</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="result">The root element is not 'result'.</s:assert>
<s:assert test="result/text()='value'">Root element does not contain text 'value'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
