The applications in Ubiquitous Computing (UbiComp) environments must be aware of their contexts of interest and adapt to changes in them. Thus, a major research challenge in the area of UbiComp is related to context awareness. Considering the high distribution, heterogeneity, dynamism, and mobility of ubiquitous environments, this paper presents an architecture for context awareness, named UbiC (Ubiquitous Context awareness), which is integrated to EXEHDA middleware (Execution Environment for Highly Distributed Applications). We consider that the main contribution of this work is an architecture that enables the acquisition, storage, and processing of context data, in a distributed way, independently of the application, in a rule-based autonomic perspective, and with support to mobility. To assess the functionalities of the UbiC architecture, we present a case study, highlighting prototypes developed, technologies employed, and tests realized.