1. A semantic publish/subscribe system enabling semantic event routing and which allows publishers to use self-defined event schemas to publish events and subscribers to use self-defined event schemas to subscribe to events comprising: an ontology repository for storing object-oriented ontologies; an ontology engine accessing said ontology repository in response to queries; a set of event publish API (Application Program Interface) that allows an event provider to publish events using self-defined event schema of their own choice; event providers who publish events using self-defined event schemas of their own choice using said set of event publish API; a set of event subscription API that allows subscribers to subscribe to events using their own self-defined event schema; event consumers who subscribe to events using their own self-defined event schemas using said set of subscription API, where the subscriptions can be modeled as SQL (Structured Query Language) statements; and an event broker which queries the ontology engine to identify event sources for subscriptions and rewrites SQL statements to bridge semantic differences between published events and information required by subscriptions and, when an event is published, routes the event based on a rewritten SQL statement.