Detecting and resolving the interaction between telephone features: terminating call screening and call forwarding by colored Petri-nets

This paper presents an approach for detecting and resolving feature interactions (FI) in a telephone system. In this approach, the existing system and new features are each represented as a colored Petri net (CP-net), and a service of a feature is represented as a firing sequence realizing a transition-invariant (T-invariant) of that Petri net. When two features are integrated into a system, their interaction can be observed through combining their nets into a large net. If some relevant T-invariants of the two component nets are not preserved, an FI is detected in the integrated system; and if they are preserved, FI has been resolved. As an illustration, this approach is applied to detecting and resolving the interaction between the two features: terminating call screening and call forwarding.