Abstract. The availability of portable computing devices and advances in wireless networking technologies have contributed to the growing acceptance of mobile computing applications and opened the door for the possibility of seamless and pervasive services in mobile environments. However, with the dilemmas of limited device capabilities, network connectivity, transmission range and frequent changes, due to users and/or devices mobility, Internet-oriented wireless applications face challenges in terms of computation and interaction. These challenges elaborate with the inevitable demand for such applications to adapt to users' situations, their profiles, and the resources provided by the operating environment. Taking into account contextual information is an essential ingredient to cope with the frequent changes in mobile environments and hence provide adequate solutions for achieving adaptability, reliability, and seamless service provisioning. This paper introduces the use of policies over semantically modeled context as a technique for generating implicit context information and making use of context in mobile computing in general and internet-computing in specific. A context-sensitive instant messaging application demonstrates our proposed model using agent technology.