Towards SDL specification of a European OSI-application layer protocol interface for wired personalized communications and distributed multimedia applications

In this paper, we present a formal specification of CSTA, a protocol interface that links the telecommunications and data processing environments to support a variety of distributed telecommunications applications. We specify it in SDL, the ITU/TSS (formerly, CCITT) standard description technique for telecommunications protocols and distributed systems. In CSTA, an application is a cooperative process between a telecommunications switching function and computing function. It is presented to the user as a single function providing enhanced services. The switching function and the computing function are typically distributed among a telecommunications network and a computer network. The interface allows flexible creation of new telecommunications services and applications. It allows computer users and applications to invoke telecommunications services on the switch. The interface protocol has applications in Intelligent Networks, Customization of Telecommunications Services, Multimedia Communications, and Universal Personalized Communications.