Dynamic Binding in Mobile Applications: A Middleware Approach

Service development and deployment face new challenges from the wide availability of Internet points of attachment, increasing deployment of wireless networks, and growing portabledevice market. To provision traditional Internet services to mobile clients, service providers must address the possibility of roaming during service sessions and the heterogeneity of access-terminal hardware and software. In addition, mobile computing encourages the development of location-dependent services. Traditional middleware solutions are not designed to handle mobile users, their frequent temporary disconnection, or the wide range of access devices they employ. Novel middleware components should extend the fixed Internet infrastructure at service provisioning time when necessary to accommodate user and device mobility.1 The middleware should also propagate to the service-level system information such as user location, preference profiles, and device characteristics. The mobility of users, terminals, and service components requires novel middleware solutions to handle the set of bindings to needed resources. We have developed a middleware approach for binding management in mobile applications that addresses several of these issues. The Contextand Location-based Middleware for Binding Adaptation (Colomba) automatically updates mobile client references to needed resources whenever a client moves and dynamically selects and enforces the most suitable binding strategy. Colomba operates according to dynamic environmental conditions and various metadata, ranging from administrator management requirements to user, terminal, resource profiles, and resource co-locality constraints — forcing two resources to reside close to each other and eventually move together, for instance. Our middleware lets service providers express binding strategies at a high level of abstraction in terms of declarative directives that are cleanly separated from the service code; changes in binding