Why can't I specify input and output document?

pipe below fails in Calabash .9

<?xml version="1.0"?>
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc">
 <p:input port="source" primary='true'>
   <p:document href="doc.xml"/>
 </p:input>
 <p:output port='result'>
   <p:document href="op.xml"/>
 </p:output>
 <p:identity/>
</p:declare-step>


I want to define a pipe with both input and output files specified by the pipe.

http://www.w3.org/TR/xproc/#c.xslt
seems to specify both, I'm unsure why mine doesn't work?

Error  : file:/files/xproc/tests/pipe3.xpl:2: Unbound primary output
port on last step: #ANON.85
Error  : Pipeline failed: com.xmlcalabash.core.XProcException: Don't
know how to handle binding 3


Any suggestions where / why I'm wrong please?



-- 
Dave Pawson
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