The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" xmlns:test="http://test" version="3.0">
<p:output port="result"/>
<p:declare-step type="test:step">
<p:option name="opt1" select="'text'"/>
<p:option name="opt2" select="concat($opt1,'_1')"/>
<p:option name="opt3" select="concat($opt2,'_2')"/>
<p:output port="result"/>
<p:identity>
<p:with-input>
<result>{$opt1} {$opt2} {$opt3}</result>
</p:with-input>
</p:identity>
</p:declare-step>
<test:step opt3="opt3"/>
</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 document root is not 'result'.</s:assert>
<s:assert test="result/text()='text text_1 opt3'"/>
</s:rule>
</s:pattern>
</s:schema>
