Customers' requirements written in a natural language are rewritten to modeling language in development phases. In many cases, those who participate in development cannot understand requirements written in modeling language. This paper proposes the translation technique from the requirement model which is written by REED(REquirement EDitor) tool into a natural language in order to help for the customer understanding requirement model. This technique consists of three phases: 1 st phase is

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... ting the IORT(Input-Output Relation Tree), 2 nd phase is generating the RTT(Requirement Translation Tree), 3 rd phase is translating into a natural language.