In ubiquitous computing environment a large number of devices, services and applications that help end-users perform various kinds of tasks. Especially Location awareness based on TPO (Time-Position- Occasion) significantly enhances the functionality of ubiquitous computing services and applications. For these, a plethora of different alternative of complementary LBS (Location Based System) and RFID technologies is available. However, these technologies give TPO information in different formats and with different meanings. In this paper we propose Situation-Middleware that helps we do access control of suitable applications, service and devices without considering technologies. Besides, we introduce an inference rule based on Event-Condition-Action and TPO metadata. Using TPO metadata is able to keeping clear of semantics mistakes which are entered from ubiquitous devices. The inference rule allows inferring that actions may conflicts based on policy.