Cooperation plays an important role in distributed reasoning systems in Ambient Environment. In such systems, ambient entities with diverse perception and capabilities have to cooperate during the reasoning process by sharing parts of their local knowledge to achieve a set of common goals. Nevertheless, previous work in distributed reasoning assumedthat ambient entities keep their local knowledge private and reason in a top-down manner to reach these goals. Such approaches do not fit with the features of Ambient environment. This paper presents a more tailored distributed peer-to-peerapproach for modeling and reasoning with context informationusing cooperation in Ambient Environment. Ambient entitiescooperate by sharing parts of their local context informationand reason in a bottom-up manner. We propose an operational model and present a prototype implementation for the proposed approach