<filter name="step1" module="importer" act="procImporterAdminStep1">
    <form>
        <node target="source_type" required="true" filter="alpha" />
    </form>
    <parameter />
    <response callback_func="completeStep1">
        <tag name="error" />
        <tag name="message" />
        <tag name="next_step" />
        <tag name="module_list" />
    </response>
</filter>
