Why rules on the Semantic Web?

• There are conditions that ontologies (ie, OWL) cannot express

• • a well known example is Horn rules: (P1 ∧ P2 ∧ …) → C
  • • (the property chains of OWL 2 covers some cases)

• But there are conditions that are complicated in rules and ontologies are better

• A different way of thinking — people may feel more familiar in one or the other