An Environment for the Creationof Intelligent Network

This paper presents a Service Creation Environment which is unique in ooering global correctness and consistency checks. These guarantee frame conditions for the design concerning implementability, country speciic standards and network speciic features. Frame conditions are formulated in a modal logic and veriied via model checking. The described environment ooers a lazy and incremental use of formal methods: if no formal constraints are deened, the system behaves like standard systems for service creation. However, the more constraints are added, the more reliable are the created services. This provides a `soft' entry into the world of formal methods. Intelligent Network (IN) services are customized telephone services, like e.g., 1) `Free-Phone', where the receiver of the call can be billed if some conditions are met, 2) `Virtual Private Network', enabling groups of customers to deene their own private net within the public net, or 3) `Partner Lines', where a number of menus leads to the satisfaction of all desires. The realization of these services is quite complex and error prone. The current trend in advanced IN services clearly evolves towards decoupling Service Processing Systems from the switch network (see e.g. CrKu94]). The reasons for this tendency lie in the growing need for decentralization of the service processing, in the demand for quick customization of the ooered services, and in the requirement of rapid availability of the modiied or reconngured services. Service Processing Systems are those elements of the IN architecture which provide service processing logic and control but not connection control and management, which are provided by the underlying switch system. In particular, they include Service Creation Environments 1 , which are interactive environments responsible for the creation, modiication, customization and provision of new services. Service Creation Environments for the creation of IN-services are usually based on clas-sicaìClipboard-Architecture' environments, where services are graphically constructed, compiled, and successively tested. Two extreme approaches characterize the state of the art: The rst approach guarantees consistency, but the creation process is strongly limited in its exibility to compose Service Independent Building Blocks (SIBs) to new services. The second approach allows exible compositions of services, but there is little or no feedback on the correctness of the service under creation during the development: the validation is almost entirely located after the design is completed. Thus the resulting test phase is lengthy and costly. This paper presents an environment used for the reliable, aspect-driven creation of telephone services …