Towards testability-directed Estelle specification of an OSI-IN interface for universal personal communications and multimedia communications

We present a protocol interface, called CSTA, that links the telecommunications and data processing environments to support a variety of applications. We specify it in Estelle, one of ISO´s standard description techniques for communications protocols and distributed systems. CSTA allows flexible creation of new telecommunications services and applications. It allows computer users and applications to invoke telecommunications services on the switch. CSTA protocol has applications in intelligent networks, customization of telecommunications services, multimedia communications, and personalized communications. The formalization of the CSTA is testability-directed. A testability-directed standard protocol is a version of the protocol standard that reflects the degree of precision in developing universal interpretation of what it means for an implementation to conform to the standard, and the ability to exercise the implementations of a communications protocol for purposes of assessing their conformance to the standard