A socio-technical system (STS) consists of many different actors such as people, organizations, software applications and infrastructures. We call actors except both people and organizations machines. Machines should be carefully introduced into the STS because the machines are beneficial to some people or organization but harmful to others. We thus propose a goal-oriented requirements modelling language called GDMA based on i* so that machines with the following characteristics can be systematically specified. First, machines make the goals of each people be achieved more and better than ever. Second, machines make people achieve goals fewer and easier than ever. We also propose analysis techniques of GDMA to judge whether or not the introduction of machines are appropriate or not. Several machines are introduced into an as-is model of GDMA locally with the help of model transformation techniques. Then, such an introduction is evaluated globally on the basis of metrics derived from the model structure. We confirmed that GDMA could evaluate the successful and failure of existing projects.