A formalisation of the ITU-T Intelligent Network standard

Telecommunication systems are today among the largest and most heterogeneous computer systems that exist. The functionality offered by them is rapidly increasing, by numerous features: call waiting, credit-card billing and call-forwarding to name a few. The realisation of extra services poses a challenge to implementors, in particular since different services are developed at different times and places, by different people. Not only is the number and complexity of services increasing but some vendors want to enable users to tailor their own services and ultimately design them entirely. This of course calls for rigorous control of the services so that they do not come into conflict with the interest of the vendors, other users or surprise the users with their behaviours. One way of aiding the service designers is to provide a service creation environment containing a set of well defined building blocks that would be uniform for all features, irrespective of vendor or service. Such an environment also needs tool support for writing, checking, validating and analysing for possible conflicts. We have constructed a formalism for compactly specifying the interface behaviour of the switching and service logic system underlying a service creation environment, and for specifying the behaviour of components of an environment for service creation. For this formalism we supply tool support in the form of a simulator. We have further made a formalisation, in our framework, of the ITU-T Intelligent Network model, Capability Set-1. The formalisation concerns both the underlying service architecture, in which service logic is perform by a dedicated Service Control Function, and the component language, in which Service Independent Building Blocks are composed to yield new services