1. A method of interaction between a requesting entity including at least one SIP based resource and a processor and a responding entity including at least one SIP based resource and a processor, on a communication network based on session initiation protocol, comprising the steps of: retrieving, by the requesting entity, a machine-readable service description from a service description provider, the machine-readable service description comprising specifications of interaction between the requesting entity invoking a service and the responding entity offering the service, said specifications comprising at least a set of rules comprising abstract input/output message formats and session initiation protocol binding rules, wherein the abstract input message format comprises information relating to invoking the service by the requesting entity, and wherein the abstract output message format comprises information relating to the service provided by the responding entity; invoking, by the requesting entity, the service to a session initiation protocol uniform resource identifier by means of a session initiation protocol invocation message patterned according to said retrieved machine-readable service description; interpreting, by the requesting entity, the service provided by the responding entity according to said machine-readable service description; receiving, by at least one of the requesting entity or the responding entity, a dynamic notification regarding an updated machine-readable service description comprising the specifications of interaction; and retrieving, by the requesting entity, the updated machine-readable service description including the session initiation protocol binding rules.
11. The method according to claim 1 , wherein the step of providing said machine-readable service description comprises the steps of: creating said machine-readable service description; and making available said machine-readable service description to the requesting entity.