1. A computer readable medium including program code for providing a message-based interface for exchanging business rules between parties, the medium comprising: program code for receiving via a message-based interface exposing at least one service as defined in a service registry and from a heterogeneous application executing in an environment of computer systems providing message-based services, a first message for providing a statement of a specific condition or combination of conditions and an appropriate action to take or an object to use if the conditions are fulfilled that includes a message package hierarchically organized as: a business rule message entity; and a business rule package comprising a business rule entity, where the business rule entity includes a universally unique identifier (UUID), a version identifier, a status, an activation status code, a business rule application UUID, and system administration data; and program code for sending a second message to the heterogeneous application responsive to the first message.