A smart home service is provided by following several contexts of environment and user activities. Moreover, some contexts are common for different services. So, it is unwise to separately compute the same context for different services due to the processing time cost, here a context reusable mechanism can significantly reduce the context computing cost. For this purpose, middleware-based implementation is a good alternative. Middleware uses raw data through sensors and user profiles from database then generates context using these data, and finally conveys context to applications. In this paper, we propose a middleware architecture that shares context in a cooperative manner so that it can be reused among applications. Basically, this middleware generates a particular context at once for a time interval and disseminates among registered applications using a new mechanism. Measuring inequality of the context computing time over application-based implementation exposes the effectiveness of this middleware.