The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" name="pipeline" version="3.0">
<p:output port="result"/>
<p:wrap match="section" wrapper="foo">
<p:with-input>
<doc>
<section>
<title>some title</title>
<section>
<title>some title</title>
<section>
<title>some title</title>
</section>
<section>
<title>some title</title>
</section>
</section>
</section>
</doc>
</p:with-input>
</p:wrap>
</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">Root element is not 'doc'.</s:assert>
<s:assert test="doc/foo">Element 'doc' does not have a child 'foo'.</s:assert>
<s:assert test="doc/foo/section">Element 'doc/foo' does not have child 'section'.</s:assert>
<s:assert test="doc/foo/section/title">Element 'doc/foo/section' does not have child 'title'.</s:assert>
<s:assert test="doc/foo/section/foo">Element 'doc/foo/section' does not have child 'foo'.</s:assert>
<s:assert test="doc/foo/section/foo/section">Element 'doc/foo/section/foo' does not have child 'section'.</s:assert>
<s:assert test="doc/foo/section/foo/section/title">Element 'doc/foo/section/foo/section' does not have child 'title'.</s:assert>
<s:assert test="count(doc/foo/section/foo/section/foo)=2">Element 'doc/foo/section/foo/section' does not have two child elements 'foo'.</s:assert>
<s:assert test="count(doc/foo/section/foo/section/foo/section)=2">Element 'doc/foo/section/foo/section' does not have two child elements 'foo/section'.</s:assert>
<s:assert test="count(doc/foo/section/foo/section/foo/section/title)=2">Element 'doc/foo/section/foo/section' does not have two child elements 'foo/section/title'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
