1. A computer readable medium including program code for providing a message-based interface for exchanging specifications of communication systems that includes services, communication methods and technical settings needed for communication, 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 a specification of a communication system that includes services, communication methods, and technical settings needed for communication that includes a message package hierarchically organized as: a communication system query message entity; and a communication system package comprising a communication system entity, where the communication system entity includes a universally unique identifier (UUID) an identifier (ID), a system access type code, a hypertext transfer protocol (HTTP) proxy name, system administrative data, and a status; and program code for sending a second message to the heterogeneous application responsive to the first message.