The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:input port="source"/>
<p:output port="result"/>
<p:for-each name="for">
<p:with-input select="//para"/>
<p:choose>
<p:when test="p:iteration-position() = 1">
<p:identity>
<p:with-input port="source">
<p:inline>
<first/>
</p:inline>
<p:pipe step="for" port="current"/>
</p:with-input>
</p:identity>
</p:when>
<p:when test="p:iteration-position() = p:iteration-size()">
<p:identity>
<p:with-input port="source">
<p:pipe step="for" port="current"/>
<p:inline>
<last/>
</p:inline>
</p:with-input>
</p:identity>
</p:when>
<p:otherwise>
<p:identity/>
</p:otherwise>
</p:choose>
</p:for-each>
<p:wrap-sequence wrapper="wrapper"/>
</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="wrapper">The document root is not wrapper.</s:assert>
<s:assert test="wrapper/*[1]/name()='first'">First child of wrapper is not 'first'.</s:assert>
<s:assert test="wrapper/*[2]/name()='para'">Second child of wrapper is not 'para'.</s:assert>
<s:assert test="wrapper/*[3]/name()='para'">Third child of wrapper is not 'para'.</s:assert>
<s:assert test="wrapper/*[4]/name()='para'">Fourth child of wrapper is not 'para'.</s:assert>
<s:assert test="wrapper/*[5]/name()='last'">Fifth child of wrapper is not 'last'.</s:assert>
<s:assert test="count(wrapper/*)=5">Wrapper does not have five children.</s:assert>
<s:assert test="wrapper/para[1]/text()='Paragraph 1.'">Content of first para child is not 'Paragraph 1.'</s:assert>
<s:assert test="wrapper/para[2]/text()='Paragraph 2.'">Content of second para child is not 'Paragraph 2.'</s:assert>
<s:assert test="wrapper/para[3]/text()='Paragraph 3.'">Content of thrid para child is not 'Paragraph 3.'</s:assert>
</s:rule>
</s:pattern>
</s:schema>
