1. A computer readable medium including program code for providing a message-based interface for exchanging information about events and user input for which users are notified in a feed system, 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 querying information about feed events according to specified selection elements, the first message including a message package hierarchically organized as: a feed event query message entity; and a feed event package comprising a feed event entity, where the feed event entity includes a universally unique identifier (UUID) and system administrative data, and where the feed event entity comprises at least one creation identity entity; and program code for sending a second message to the heterogeneous application responsive to the first message.