The Semantic Application Design Language (SADL) expresses domain knowledge as semantic models and rules. The SADL-IDE (integrated development environment) is an Eclipse plug-ins for editing SADL, converting to OWL, and testing using Jena or Pellet.
JNOMO is a Jean Plugin for providing more expresiveness in its rule language. This plugin allows for retracting or priorizing rules, removing facts as a rule consecuence or even asking for the "unspecified" information into Knowledge Base.