1. A computer readable medium including program code for providing a message-based interface for exchanging information about relations between sales territories and accounts, 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 requesting maintenance of one or more relations between sales territories and accounts that includes a message package hierarchically organized as: a sales territory account bundle check maintain request message entity; a message header package comprising a basic message header entity; and a sales territory package comprising a sales territory account maintain request bundle entity, where the sales territory account maintain request bundle entity includes a sales territory identifier (ID); and program code for sending a second message to the heterogeneous application responsive to the first message.