FEATURE INTERACTIONS AND FORMAL SPECIFICATIONS IN TELECOMMUNICATIONS

The de facto specification of a telecommunications system is a set of feature specifications. A feature interaction occurs when the behavior of the system as a whole does not satisfy the separate specifications of all its features. Much of this problem results from the rapid evolution of telecommunications technology. Innovations such as multiplexing telephones, flexible calls. multipurpose directory numbers, and greater distribution of function undermine what used to be fundamental assumptions. Many feature interactions can be eliminated by using current general-purpose specification techniques in the feature specifications (for example, types, roles, invariants, and parsing). But other feature interactions call for application-dependent specification techniques based on the status of features in telecommunications as primary, named, manipulable objects. Unfortunately, all of these techniques remove feature interactions only if system designers restructure old specifications and write new ones with foresight. Designers will also have to better separate the system's concerns and emphasize creating conceptual models that can be exploited as new features are developed.