A semantic publish/subscribe system enables semantic event routing and allows publishers (resp. subscribers) to use self-defined event schemas to publish (resp. subscribe) events. The constraints on value-based publish/subscribe systems that publishers and subscribers must share the same event schemas are removed. With ontology support, the system conducts event correlation based on their semantics using relational operators. Event sources are searched for subscriptions and selected events are automatically correlated according to subscriptions. The system enables efficient semantic event routing by rewriting the subscription SQL statement, wherein no redundant events are generated.