Toshinori Takai (AIST CVS/JST CREST) A case study of applying formal methods for developping a network system Abstract: We are working with a company to research, design, develop and verify the network system. In the last year, we tried to prove security properties of the network system. In this year, we are tring to find bugs in the specifiations of the system by a model-checking technique and to find bugs in the implementation of the system by testing. In this presentation, we report a case study of formal methods on the practical view point.