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Wireless connectivity and widespread diffusion of portable devices offer novel opportunities for users to share resources anywhere and anytime, and to form ad-hoc coalitions. Resource access control is crucial to leverage these ad-hoc collaborations. In pervasive scenarios, however, collaborating entities cannot be predetermined and resource availability(More)
Policies are being increasingly used for automated system management and controlling the behavior of complex systems, allowing administrators to modify system behavior without changing source code or requiring the consent or cooperation of the components being governed. Past approaches to policy representation have been restrictive in many ways. By way of(More)
— The provisioning of Web services over the wireless Internet introduces novel challenging issues for service design and implementation: from user/terminal mobility during service execution, to wide heterogeneity of portable access devices and unpredictable modifications in accessible resources. In this scenario, there are frequent provision-time changes in(More)
S ociality characterizes an individual's life: people go to bars and restaurants, study together in schools, and work in teams on production lines and in business. Every person plays a role within a social community. Social ties, such as friendship, common interests, and shared professional activities, bind individuals together. This web of social bindings(More)
The widespread diffusion of mobile computing calls for novel services capable of providing results that depend on both the current physical position of users (location) and the logical set of accessible resources, subscribed services, preferences, and requirements (context). Leaving the burden of location/context management to applications complicates(More)
Wireless connectivity and the widespread diffusion of portable devices raise new challenges for ubiquitous service provisioning. Mobility of users causes frequent and unpredictable changes in user location and in consequently available resources. Access control to resources is crucial to leverage the provision of ubiquitous services and calls for novel(More)