Abstract
There is an inherent trade-off between epidemic and deterministic tree-based broadcast primitives. Tree-based approaches have a small message complexity in steady-state but are very fragile in the presence of faults. Gossip, or epidemic, protocols have a higher message complexity but also offer much higher resilience. This paper proposes an integrated broadcast scheme that combines both approaches. We use a low cost scheme to build and maintain broadcast trees embedded on a gossip-based overlay. The protocol sends the message payload preferably via tree branches but uses the remaining links of the gossip overlay for fast recovery and expedite tree healing. Experimental evaluation presented in the paper shows that our new strategy has a low overhead and that is able to support large number of faults while maintaining a high reliability.

Abstract

Abstract
Discussion forums are presently one of the most important tools in assisting distance education. Web learning is accomplished by using these communication tools and, particularly, by the interactions that take place in these settings. Therefore, students' participations in a discussion forum, the frequency and the way they participate, the types of interactions that they create with their colleagues and with the professor, can and should be analyzed in order to fully understand the group and, consequently, allow a more efficient and student focused education. In this article, suggest graphical representations (the iGraph) of these interactions and by using these tools, we describe forum participation according to the centralization of information, the density and intensity of interactions, and yet the quality of the moderation.

Abstract
The integration of multiple network access technologies in the terminal is one of the most important trends in 4G networks. This integration places telecommunications service providers, and in particular operators, under the significant challenge of being able to transform their services in order to adapt them to a great variety of delivery contexts. This paper describes a generic methodology for the adaptation of telecommunications services provided in the context of an operator. A number of scenarios are examined which show how Parlay middleware can be used by trusted service providers to easily access network resources and context information for enhancing location-based and adaptable multimedia telecommunications services.

Abstract
This paper describes the design and implementation of a PKI-based eHealth authentication architecture. This architecture was developed to authenticate eHealth Professionals accessing RTS (Rede Telematica da Saude), a regional platform for sharing clinical data among a set of affiliated health institutions. The architecture had to accommodate specific RTS requirements, namely the security of Professionals' credentials, the mobility of Professionals, and the scalability to accommodate new health institutions. The adopted solution uses short lived certificates and cross-certification agreements between RTS and eHealth institutions for authenticating Professionals accessing the RTS. These certificates carry as well the Professional's role at their home institution for role-based authorization. Trust agreements between health institutions and RTS are necessary in order to make the certificates recognized by the RTS. The implementation was based in Windows technology and as a general policy we avoided the development of specific code; instead, we used and configured available technology and services.

Abstract