The challenging task of requirements specification for communication services has not been sufficiently addressed to date. The complexity of communication systems requires a formal approach to requirements capture and analysis, however at the same time the industry does not take well to convoluted formalisms. We suggest improving requirements specification by enhancing the approach that is most popular at the moment - use case modelling. We amend traditional use case models with a formal structure and semantics to make them suitable for automated verification. The enhanced use case modelling technique that we propose is called Susan (”S”ymbolic ”us”e case ”an”alysis) and it facilitates verification of use case models using symbolic model checking. We also developed a software tool called SusanX to construct, manipulate and analyse Susan models. The analysis feature of the tool is implemented using the NuSMV model checker. A number of generic properties for verification are built into SusanX, and the tool additionally allows the user to construct model-specific properties
