The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:identity name="id1">
<p:with-input port="source">
<p:inline>
<doc/>
</p:inline>
</p:with-input>
</p:identity>
<p:identity name="id2">
<p:with-input port="source">
<p:inline>
<doc/>
</p:inline>
</p:with-input>
</p:identity>
<p:identity name="combine">
<p:with-input port="source" pipe="@id1 @id2"/>
</p:identity>
<p:variable name="a" select="count(collection())" collection="true"/>
<p:identity>
<p:with-input>
<doc>{$a}</doc>
</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="doc">The pipeline root is not “doc”.</s:assert>
<s:assert test="doc = '2'">Text collection length isn’t correct.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
