When service S is the definitiveService for property P, any statement X P Y is true iff and only if a query to S returns that it is. The protocol for the service S depends on the scheme. For mysql protocol, the URI of the service is like sql://user:password@host.domain/database/. For example, there may be a definitive service for the zipcode of airports by airport code, and so on. This is useful to let a reasoner know that it can help resolve a query by delegating it to the service in question. (Cwm will do this if its mode includes "r").