Publishers to define LogDistiller's way of publishing log distillation reports.

Each report specifies which publisher to use :

<group id="unknown">
  <description>Unknown log events : to be categorized</description>
  <condition>
      <match attribute="timestamp" type="contains">${date}</match>
  </condition>
  <report publisher="file"/>
  <report publisher="mail">
    <param name="to">admin@localhost</param>
  </report>
  <plugin type="freq">
    <param name="attribute">severity</param>
  </plugin>
</group>