Dependency management (again)

Consider the following pipeline:

<p:pipeline name="pipeline"
	    xmlns:p="http://www.w3.org/2007/03/xproc"
	    xmlns:ex="http://example.org/ns/xproc-extensions">
<p:input port="document"/>
<p:output port="result"/>

<p:declare-step type="ex:db-update">
  <p:input port="source" sequence="no"/>
  <p:parameter name="database" required="yes"/>
</p:declare-step>

<p:declare-step type="ex:db-query">
  <p:output port="result" sequence="no"/>
  <p:parameter name="database" required="yes"/>
  <p:parameter name="query" required="yes"/>
</p:declare-step>

<ex:db-update name="update">
  <p:input port="source">
    <p:pipe step="pipeline" port="document"/>
  </p:input>
  <p:parameter name="database" value="mydb"/>
</ex:db-update>

<ex:db-query name="query">
  <p:parameter name="database" value="mydb"/>
  <p:parameter name="query" value="some query"/>
</ex:db-query>

<p:xslt>
  <p:input port="stylesheet">
    <p:document href="http://example.org/xslt/format-report.xsl"/>
  </p:input>
</p:xslt>

</p:pipeline>

I don't see any way to assure that db-update runs before db-query without
adding some sort of dependency control to the language. Perhaps:

<ex:db-query name="query" depends="update">
  <p:parameter name="database" value="mydb"/>
  <p:parameter name="query" value="some query"/>
</ex:db-query>

                                        Be seeing you,
                                          norm

-- 
Norman Walsh
XML Standards Architect
Sun Microsystems, Inc.