The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:identity name="one">
<p:with-input>
<one/>
</p:with-input>
</p:identity>
<p:identity name="two">
<p:with-input>
<two/>
</p:with-input>
</p:identity>
<p:identity name="identity">
<p:with-input port="source">
<p:pipe step="one"/>
<p:pipe step="two"/>
<p:pipe step="one"/>
<p:pipe step="two"/>
</p:with-input>
</p:identity>
<p:wrap-sequence name="splitseq" wrapper="pipe-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="pipe-sequence">Root element is not 'pipe-sequence'.</s:assert>
<s:assert test="count(pipe-sequence/*)=4">Root element should have 4 children.</s:assert>
<s:assert test="pipe-sequence/*[1]/local-name()='one'">First child of root element is not 'one'.</s:assert>
<s:assert test="pipe-sequence/*[2]/local-name()='two'">Second child of root element is not 'two'.</s:assert>
<s:assert test="pipe-sequence/*[3]/local-name()='one'">Third child of root element is not 'one'.</s:assert>
<s:assert test="pipe-sequence/*[4]/local-name()='two'">Forth child of root element is not 'two'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
