The XAPI , which is an abbreviation for extensive Application Programming Interface, is an operating system and language-independent homogenous access mechanism to general communication services. It is not dedicated to a certain layer, but allows access to all layers of the OSI reference model and other layered communication models (e.g. conferencing). The XAPI provides a framework of functions for the use in communication applications. All communication services are accessible through this set of functions. The XAPI does not impose any restrictions on the service interface of the underlying communication platform.Which services are made available via the XAPI depends on the installed service providers, and not on the XAPI, which only provides the access mechanism. New service providers can be added in the XAPI configuration. Thus, the communication system can be tailored to specific requirements and all communication services are accessible via one homogeneous access mechanism.