Use Case 5.10 - XInclude and Sign

In looking at:

   http://www.w3.org/TR/xmldsig-core/

The algorithm needs the KeyInfo element.  The signature of the step would
be:

<?xml version="1.0" encoding="UTF-8"?>
<p:declare-step type="ex:sign" xmlns:p="http://www.w3.org/ns/xproc"
    xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0"
    xmlns:ex="http://www.example.org/signer">
   <p:input port="source" primary="true"/>
   <p:input port="keyinfo"/>
   <p:output port="result" primary="true"/>
</p:declare-step>

Assuming the canonicalization is built into the signing technology:

<?xml version="1.0" encoding="UTF-8"?>

<p:declare-step name="main" xmlns:p="http://www.w3.org/ns/xproc"
    xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0"
    xmlns:ex="http://www.example.org/signer">
   <p:input port="source" primary="true"/>
   <p:input port="keyinfo"/>
   <p:output port="result"/>
   <import href="signer.xpl"/>
   <p:xinclude/>
   <p:xslt>
      <p:input port="stylesheet">
         <p:document href="transform.xsl"/>
      </p:input>
      <p:input port="parameters">
         <p:inline><c:param-set/></p:inline>
      </p:input>
   </p:xslt>
   <ex:sign>
      <p:input port="keyinfo">
         <p:pipe step="main" port="keyinfo"/>
      </p:input>
   </ex:sign>
</p:declare-step>

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics