The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result">
<p:http-request href="http://localhost:8246/service/echo" method="post">
<p:with-input>
<p:inline content-type="text/html" document-properties="map{'serialization' : map{'encoding' : 'ISO-8859-1'}}">
<html/>
</p:inline>
</p:with-input>
</p:http-request>
<p:identity>
<p:with-input pipe="report">
</p:identity>
<p:identity>
<p:with-input>
<result>{.?headers?content-type}</result>
</p:with-input>
</p:identity>
</p:declare-step>
Schematron validation
<s:schema xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
<s:pattern>
<s:rule context="/">
<s:assert test="result">The root element is not 'result'.</s:assert>
<s:assert test="result/text()='text/html; charset=ISO-8859-1'">The content type is not correct.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
