"Federated Identity Management (FIdM) systems are at the heart of any on-line service in a public, private or hybrid autonomous cooperating system. This paper reviews and compares several existing approaches for building FIdM systems in the specific sector of e-Government by showing identity management schemes employed by several countries representatives of different realities by size, geographycal location and Public Administration traditions. The paper analyzes then the case of Italy by introducing the ongoing effort for defining and developing a nationwide e-Government Enterprise Architecture in order to guarantee a flexible approach for integrated application services, respecting local and central administrations’ autonomy. The paper finally focuses on the FIdM aspects employed within the Italian Enterprise Architecture."

"A distributed event notication service (ENS) is a middleware ar- chitecture commonly used to provide applications with scalable and ro- bust publish/subscribe communication primitives. A distributed ENS can route events toward subscribers using multiple paths with dier- ent lengths and latencies; as a consequence, subscribers can receive events out of order. In this paper, we propose a novel solution for out-of-order notication detection on top of an existing topic-based ENS. Our solution guarantees that events published on dierent topics will be either delivered in the same order to all the subscribers of those topics or tagged as out-of-order. The proposed algorithm is completely distributed and is able to scale with the system size while imposing a reasonable cost in terms of notication latency. Our solution improves the current state of the art solutions by dynamically handling subscrip- tions/unsubscriptions and by automatically adapting with respect to topic popularity changes."

"This paper studies the complexity of answering aggregation queries with the interval validity semantics in a distributed system prone to churn. The interval validity semantics states that the query answer must contain contributions from at least all the processes that were part of the system for the whole query execution time. Solving this problem in unstructured distributed systems with unbounded churn is impossible due to the lack of connectivity and path stability between processes. This paper presents a novel overlay management protocol, namely Virtual Tree OMP, that, under the assumption of bounded churn, maintains a structured overlay network with guaranteed con- nectivity and path stability. The resulting Virtual Tree graph is a tree-shaped topology with virtual nodes constituted by cliques of pro- cesses and virtual links constituted by multiple communication links connecting processes located in adjacent virtual nodes. This paper also introduces a distributed query algorithm that, working on top of the Virtual Tree graph, guarantees answers complying with the interval validity semantics. Finally, the paper explores through an extensive experimental analysis the performance characteristics of the overlay maintenance protocol under different churn levels."

"The design of large-scale critical infrastructures demands for innovative data dissemination services, able to jointly provide reliability and timeliness guarantees. Current middleware solutions do not address both these aspects. Indeed, fault tolerance is typically achieved at the cost of severe performance fl uctuations, or timeliness is always obtained by softening the fault-tolerance requirements. In this paper we propose to fulfill this lack by combining two dierent approaches, namely coding and gossiping. We provide a theoretical model to evaluate the potential benet of coding on the information delivery performance. These results are also conrmed by an experimental analysis conducted on a real air traffic control workload, which evidences how coding mitigates latency and overhead penalties to ensure reliable event notification."