Abstract
In this paper, we proposed a level 2 middleware with common services for controlling steel plants, which is named POSMOS. POSMOS supports eight middleware services currently, but, this paper described in detail two representative services of the common services: file service and external communication service and their respective measured performance. In the experiment section, we described the performance of the two representative services and a case using our middleware which shows better response time than the existing commercial middleware by about 32%.