The feature interaction problem in Intelligent Networks (IN) obstructs more and more the rapid introduction of new features. Checking each feature manually against each other feature is no longer feasible. We give an overview on current (verification) approaches for the off-line detection of feature-interactions, and we categorize them into specified-property approaches (which verify two separate formal descriptions against each other) and general-property approaches (which require only one description). We improve the general-property approaches by presenting a formal framework that allows to identify all potential feature interactions in the specified system. It is centered around formal definitions of the notions of "feature" and "feature interaction" which cover the functional aspects of a system. The definition of feature interaction is based on the notion of "behaviour of a feature". The telephone system is modeled by a global, structured automaton. Adding a feature is realized by adding transitions and (possibly) extending the state space, employing a specific specification style. Based on the formal definition, we derive more sophisticated detection criteria. There is already some tool support. A first case study did not only find the already known feature interactions but also two interferences which we overlooked during specification. A second, extended case study is still in progress. Since the general-property approaches complement the specified-property approaches in a certain sense, we propose to apply both approaches together in order to solve the feature interaction detection problem.

Keywords

telecommunications systems, Intelligent Networks, feature interaction problem, formal description techniques, verification, verification tools, automata, model checking

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